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BEST CURRENT PRACTICE
Errata Exist
Network Working Group                                   A. Johnston, Ed.Request for Comments: 5359                                         AvayaBCP: 144                                                       R. SparksCategory: Best Current Practice                                  Tekelec                                                           C. Cunningham                                                              S. Donovan                                                           Cisco Systems                                                              K. Summers                                                                   Sonus                                                            October 2008Session Initiation Protocol Service ExamplesStatus of This Memo   This document specifies an Internet Best Current Practices for the   Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.Abstract   This document gives examples of Session Initiation Protocol (SIP)   services.  This covers most features offered in so-called IP Centrex   offerings from local exchange carriers and PBX (Private Branch   Exchange) features.  Most of the services shown in this document are   implemented in the SIP user agents, although some require the   assistance of a SIP proxy.  Some require some extensions to SIP   including the REFER, SUBSCRIBE, and NOTIFY methods and the Replaces   and Join header fields.  These features are not intended to be an   exhaustive set, but rather show implementations of common features   likely to be implemented on SIP IP telephones in a business   environment.Johnston, et al.         Best Current Practice                  [Page 1]

RFC 5359                  SIP Service Examples              October 2008Table of Contents1. Overview ........................................................31.1. Legend for Message Flows ...................................42. Service Examples ................................................62.1. Call Hold ..................................................62.2. Consultation Hold .........................................192.3. Music on Hold .............................................382.4. Transfer - Unattended .....................................502.5. Transfer - Attended .......................................582.6. Transfer - Instant Messaging ..............................712.7. Call Forwarding Unconditional .............................772.8. Call Forwarding - Busy ....................................842.9. Call Forwarding - No Answer ...............................922.10. 3-Way Conference - Third Party Is Added .................1012.11. 3-Way Conference - Third Party Joins ....................1072.12. Find-Me .................................................1132.13. Call Management (Incoming Call Screening) ...............1252.14. Call Management (Outgoing Call Screening) ...............1322.15. Call Park ...............................................1352.16. Call Pickup .............................................1472.17. Automatic Redial ........................................1542.18. Click to Dial ...........................................1633. Security Considerations .......................................1664. Acknowledgements ..............................................1665. References ....................................................1675.1. Normative References .....................................1675.2. Informative References ...................................168Johnston, et al.         Best Current Practice                  [Page 2]

RFC 5359                  SIP Service Examples              October 20081.  Overview   This document provides example call flows detailing a SIP   implementation of the following traditional telephony services:           Call Hold                        3-Way Conference           Consultation Hold                Find-Me           Music on Hold                    Incoming Call Screening           Unattended Transfer              Outgoing Call Screening           Attended Transfer                Call Park           Instant Messaging Transfer       Call Pickup           Unconditional Call Forwarding    Automatic Redial           Call Forwarding on Busy          Click to Dial           Call Forwarding on No Answer   Note that the Single Line Extension call flow has been removed from   this document and will be covered in a separate document.   The call flows shown in this document were developed in the design of   a SIP IP communications network.  They represent an example set of   so-called IP Centrex services or PBX services.   It is the hope of the authors that this document will be useful for   SIP implementers, designers, and protocol researchers alike and will   help further the goal of a standard implementation ofRFC 3261   [RFC3261] and some of its extensions.   These flows represent carefully checked and working group reviewed   scenarios of SIP service examples as a companion to the   specifications.   These call flows are based on the current version 2.0 of SIP inRFC3261 [RFC3261] with Session Description Protocol (SDP) usage   described inRFC 3264 [RFC3264].  Other RFCs also form part of the   SIP standard and are used and referenced in these call flows.   The SIP specification and the other referenced documents are   definitive as far as protocol issues are concerned.  Also, these   flows do not represent the only way to implement these services --   other approaches such as 3pcc (Third Party Call Control) [RFC3725] or   Back-to-Back User Agents (B2BUAs) can be used.  This specification   does not preclude these or other approaches for implementing such   services.  The peer-to-peer design and principles of these service   examples are described in the Multiparty Framework document   [FRAMEWORK].Johnston, et al.         Best Current Practice                  [Page 3]

RFC 5359                  SIP Service Examples              October 2008   These flows assume the functionality described in the SIP Call Flow   Examples document [RFC3665], which explores basic SIP behavior.  Some   of the scenarios described herein make use of the SIP method   extension REFER [RFC3515], the SIP header extension Replaces   [RFC3891], and the SIP header extension Join [RFC3911].  The SIP   Events document [RFC3265] describes the use of SUBSCRIBE and NOTIFY,   while the SIP Dialog Event Package document [RFC4235] describes the   dialog event package.  Some examples make use of the GRUU (Globally   Routable User Agent URI) extension [GRUU].   These flows were prepared assuming a network of proxies, registrars,   and other SIP servers.  The use of Secure SIP URIs (sips) is shown   throughout this document, implying TLS transport on each hop with   assumed certificate validation.  However, other security approaches   can be used.  The use of Digest authentication is shown in some   examples.   The emphasis in these call flows is the SIP signaling exchange.  As a   result, only very simple SDP offer/answer exchanges are shown with   audio media.  These flows apply equally well for other media and   multimedia sessions.  For more advanced examples of SDP offer/answer   exchanges, refer to [RFC4317].   Each call flow is presented with a textual description of the   scenario, a message flow diagram showing the messages exchanged   between separate network elements, and the detailed contents of each   message shown in the diagram.   For simplicity in reading and editing the document, there are a   number of differences between some of the examples and actual SIP   messages.  For example, the HTTP Digest responses are not actual MD5   encodings.  Call-IDs are often repeated, and CSeq counts often begin   at 1.  Header fields are usually shown in the same order.  Usually   only the minimum required header field set is shown.  Also, message   body content lengths are often not calculated, but instead shown as   "..." where the actual octet count would be.1.1.  Legend for Message Flows   Dashed lines (---) represent control messages that are mandatory to   the call scenario.  These control messages can be SIP signaling.   Double dashed lines (===) represent media paths between network   elements.   Messages with parentheses around the name represent optional control   messages.Johnston, et al.         Best Current Practice                  [Page 4]

RFC 5359                  SIP Service Examples              October 2008   Messages are identified in the figures as F1, F2, etc.  This   references the message details in the table that follows the figure.   Lines longer than 72 characters are handled using the <allOneLine>   convention defined inSection 2.1 of RFC 4475 [RFC4475].   Comments in the message details are shown in the following form:   /* Comments. */Johnston, et al.         Best Current Practice                  [Page 5]

RFC 5359                  SIP Service Examples              October 20082.  Service Examples2.1.  Call Hold            Alice           Proxy            Bob             |    INVITE F1   |              |             |--------------->|              |             |                |   INVITE F2  |             |(100 Trying) F3 |------------->|             |<---------------|              |             |                |180 Ringing F4|             | 180 Ringing F5 |<-------------|             |<---------------|              |             |                |  200 OK F6   |             |    200 OK F7   |<-------------|             |<---------------|              |             |     ACK F8     |              |             |--------------->|    ACK F9    |             |                |------------->|             |    Both way RTP Established   |             |<=============================>|             |                |INVITE(hold) F10             |INVITE(hold) F11|<-------------|             |<---------------|              |             |    200 OK F12  |              |             |--------------->|   200 OK F13 |             |                |------------->|             |                |     ACK F14  |             |     ACK F15    |<-------------|             |<---------------|              |             |           No RTP Sent!        |             |                |  INVITE F16  |             |   INVITE F17   |<-------------|             |<---------------|              |             |   200 OK F18   |              |             |--------------->|  200 OK F19  |             |                |------------->|             |                |    ACK F20   |             |     ACK F21    |<-------------|             |<---------------|              |             |    Both way RTP Established   |             |<=============================>|             |     BYE F22    |              |             |--------------->|   BYE F23    |             |                |------------->|             |                |   200 OK F24 |             |    200 OK F25  |<-------------|             |<---------------|              |Johnston, et al.         Best Current Practice                  [Page 6]

RFC 5359                  SIP Service Examples              October 2008   In this scenario, Alice calls Bob, then Bob places the call on hold.   Bob then takes the call off hold, then Alice hangs up the call.  Note   that hold is unidirectional in nature.  However, a UA that places the   other party on hold will generally also stop sending media, resulting   in no media exchange between the UAs.  Older UAs may set the   connection address to 0.0.0.0 when initiating hold.  However, this   behavior has been deprecated in favor or using the a=inactive SDP   attribute if no media is sent, or the a=sendonly attribute if media   is still sent.   Also note the use of the rendering feature tag defined inRFC 4235   [RFC4235] used in F10 and F11 to indicate that Bob's UA is no longer   rendering media to Bob, i.e., that Bob has placed the call on hold.   Message Details      F1 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 INVITE Proxy 1 -> Bob      INVITE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061Johnston, et al.         Best Current Practice                  [Page 7]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F3 (100 Trying) Proxy 1 -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F4 180 Ringing Bob -> Proxy 1      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159Johnston, et al.         Best Current Practice                  [Page 8]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content Length:0      F5 180 Ringing Proxy 1 -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content Length: 0      F6 200 OK Bob -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                  [Page 9]

RFC 5359                  SIP Service Examples              October 2008      F7 200 OK Proxy 1 -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F8 ACK Alice -> Proxy 1      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf92      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F9 ACK Proxy 1 -> Bob      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837492.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061Johnston, et al.         Best Current Practice                 [Page 10]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bK74bf92       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      /* Bob places Alice on hold.  Note that the version is         incremented in the o= field of the SDP. */      F10 INVITE Bob -> Proxy 1      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      F11 INVITE Proxy 1 -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061Johnston, et al.         Best Current Practice                 [Page 11]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      /* Alice replies to hold. */      F12 200 OK Alice -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 12]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F13 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F14 ACK Bob -> Proxy 1      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds72      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 ACKJohnston, et al.         Best Current Practice                 [Page 13]

RFC 5359                  SIP Service Examples              October 2008      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F15 ACK Proxy 1 -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds72       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      /* Bob takes the call off hold. */      F16 INVITE Bob -> Proxy 1      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds73      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.comJohnston, et al.         Best Current Practice                 [Page 14]

RFC 5359                  SIP Service Examples              October 2008      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F17 INVITE Proxy 1 -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837493.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds73       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F18 200 OK Alice -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837493.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds73       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 INVITEJohnston, et al.         Best Current Practice                 [Page 15]

RFC 5359                  SIP Service Examples              October 2008      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F19 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds73       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F20 ACK Bob -> Proxy 1      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds74      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70Johnston, et al.         Best Current Practice                 [Page 16]

RFC 5359                  SIP Service Examples              October 2008      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F21 ACK Proxy 1 -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837494.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds74       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      /* RTP Media stream re-established.  Alice disconnects. */      F22 BYE Alice -> Proxy 1      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf97      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F23 BYE Proxy 1 -> Bob      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837497.1Johnston, et al.         Best Current Practice                 [Page 17]

RFC 5359                  SIP Service Examples              October 2008      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf97       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F24 200 OK Bob -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837497.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf97       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F25 200 OK Proxy 1 -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf97       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 18]

RFC 5359                  SIP Service Examples              October 20082.2.  Consultation Hold           Alice            Proxy           Bob                Carol             |                |              |                   |             |    INVITE F1   |              |                   |             |--------------->|   INVITE F2  |                   |             |                |------------->|                   |             |(100 Trying) F3 |              |                   |             |<---------------|180 Ringing F4|                   |             |                |<-------------|                   |             | 180 Ringing F5 |              |                   |             |<---------------|  200 OK F6   |                   |             |                |<-------------|                   |             |    200 OK F7   |              |                   |             |<---------------|              |                   |             |     ACK F8     |              |                   |             |--------------->|     ACK F9   |                   |             |                |------------->|                   |             |     Both way RTP Established  |                   |             |<=============================>|                   |             |                |INVITE(hold) F10                  |             |INVITE(hold) F11|<-------------|                   |             |<---------------|              |                   |             |    200 OK F12  |              |                   |             |--------------->|   200 OK F13 |                   |             |                |------------->|                   |             |                |     ACK F14  |                   |             |                |<-------------|                   |             |    ACK F15     |              |                   |             |<---------------|              |                   |             |         No RTP Sent!          |                   |             |                |   INVITE F16 |                   |             |                |<-------------|                   |             |                |              |    INVITE F17     |             |                |--------------------------------->|             |                |(100 Trying) F18                  |             |                |------------->|                   |             |                |              | 180 Ringing F19   |             |                |<---------------------------------|             |                | 180 Ringing F20                  |             |                |------------->|                   |             |                |              |    200 OK F21     |             |                |<---------------------------------|             |                |   200 OK F22 |                   |             |                |------------->|                   |             |                |    ACK F23   |                   |             |                |<-------------|                   |             |                |              |      ACK F24      |Johnston, et al.         Best Current Practice                 [Page 19]

RFC 5359                  SIP Service Examples              October 2008             |                |--------------------------------->|             |                |         Both way RTP Established |             |                |              |<=================>|             |                |   BYE F25    |                   |             |                |<-------------|                   |             |                |              |       BYE F26     |             |                |--------------------------------->|             |                |              |    200 OK F27     |             |                |<---------------------------------|             |                |   200 OK F28 |                   |             |                |------------->|                   |             |                |   INVITE F29 |                   |             |    INVITE F30  |<-------------|                   |             |<---------------|              |                   |             |    200 OK F31  |              |                   |             |--------------->|   200 OK F32 |                   |             |                |------------->|                   |             |                |     ACK F33  |                   |             |                |<-------------|                   |             |    ACK F34     |              |                   |             |<---------------|              |                   |             |     Both way RTP Established  |                   |             |<=============================>|                   |             |    BYE F35     |              |                   |             |--------------->|    BYE F36   |                   |             |                |------------->|                   |             |                |   200 OK F37 |                   |             |                |<-------------|                   |             |  200 OK F38    |              |                   |             |<---------------|              |                   |             |                |              |                   |   In this scenario, Alice calls Bob.  Bob places call on hold.  Bob   calls Carol.  Bob then disconnects with Carol, then takes the call   with Alice off hold.  The call ends when Alice hangs up.   Also note the use of the rendering feature tag defined inRFC 4235   [RFC4235] used in F10 to indicate that Bob's UA is no longer   rendering media to Bob, i.e., that Bob has placed the call on hold.   Message Details      F1 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70Johnston, et al.         Best Current Practice                 [Page 20]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 INVITE Proxy 1 -> Bob      INVITE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 21]

RFC 5359                  SIP Service Examples              October 2008      F3 (100 Trying) Proxy 1 -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F4 180 Ringing Bob -> Proxy 1      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content Length:0      F5 180 Ringing Proxy 1 -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content Length: 0Johnston, et al.         Best Current Practice                 [Page 22]

RFC 5359                  SIP Service Examples              October 2008      F6 200 OK Bob -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F7 200 OK Proxy 1 -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 23]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F8 ACK Alice -> Proxy 1      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf45      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F9 ACK Proxy 1 -> Bob      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837494.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf45       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 24]

RFC 5359                  SIP Service Examples              October 2008      /* Bob places Alice on hold. */      F10 INVITE Bob -> Proxy 1      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      F11 INVITE Proxy 1 -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837497.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 25]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      F12 200 OK Alice -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837497.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F13 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159Johnston, et al.         Best Current Practice                 [Page 26]

RFC 5359                  SIP Service Examples              October 2008      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F14 ACK Bob -> Proxy 1      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdsg      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F15 ACK Proxy 1 -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8374.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdsg       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567Johnston, et al.         Best Current Practice                 [Page 27]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F16 INVITE Bob -> Proxy 1      INVITE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 50170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F17 INVITE Proxy 1 -> Carol      INVITE sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749a.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFYJohnston, et al.         Best Current Practice                 [Page 28]

RFC 5359                  SIP Service Examples              October 2008      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 50170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F18 (100 Trying) Proxy 1 -> Bob      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22       ;received=192.0.2.105      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Content-Length: 0      F19 180 Ringing Carol -> Proxy 1      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749a.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Content Length:0      F20 180 Ringing Proxy 1 -> Bob      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22Johnston, et al.         Best Current Practice                 [Page 29]

RFC 5359                  SIP Service Examples              October 2008       ;received=client.chicago.example.com      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Content Length: 0      F21 200 OK Carol -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749a.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F22 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds22       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654Johnston, et al.         Best Current Practice                 [Page 30]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F23 ACK Bob -> Proxy 1      ACK sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds24      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F24 ACK Proxy 1 -> Carol      ACK sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749b.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds24       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 1 ACKJohnston, et al.         Best Current Practice                 [Page 31]

RFC 5359                  SIP Service Examples              October 2008      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F25 BYE Bob -> Proxy 1      BYE sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7j      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 2 BYE      Content-Length: 0      F26 BYE Proxy 1 -> Carol      BYE sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749k.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7j       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 2 BYE      Content-Length: 0      F27 200 OK Carol -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749k.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7j       ;received=192.0.2.105      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654Johnston, et al.         Best Current Practice                 [Page 32]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 9876543210@biloxi.example.com      CSeq: 2 BYE      Content-Length: 0      F28 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7j       ;received=192.0.2.105      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=456654      Call-ID: 9876543210@biloxi.example.com      CSeq: 2 BYE      Content-Length: 0      /* Bob takes the call off hold. */      F29 INVITE Bob -> Proxy 1      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7b      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 33]

RFC 5359                  SIP Service Examples              October 2008      F30 INVITE Proxy 1 -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749q.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7b       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F31 200 OK Alice -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749q.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7b       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 34]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F32 200 OK Proxy 1 -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7b       ;received=192.0.2.105      Record-Route: <sips:ss1.example.com;lr>      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F33 ACK Bob -> Proxy 1      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7d7      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replacesJohnston, et al.         Best Current Practice                 [Page 35]

RFC 5359                  SIP Service Examples              October 2008      Content-Length: 0      F34 ACK Proxy 1 -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8374.1      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7d7       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F35 BYE Alice -> Proxy 1      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf10      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F36 BYE Proxy 1 -> Bob      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8379.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf10       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 36]

RFC 5359                  SIP Service Examples              October 2008      F37 200 OK Bob -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8379.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf10       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F38 200 OK Proxy 1 -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf10       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 37]

RFC 5359                  SIP Service Examples              October 20082.3.  Music on Hold           Alice             Bob       Music Server             |                |              |             |    INVITE F1   |              |             |--------------->|              |             | 180 Ringing F2 |              |             |<---------------|              |             |    200 OK F3   |              |             |<---------------|              |             |     ACK F4     |              |             |--------------->|              |             |       RTP      |              |             |<==============>|              |             |                |              |             |   Bob places Alice on hold    |             |                |              |             | INVITE (hold) F5              |             |<---------------|              |             |    200 OK F6   |              |             |--------------->|              |             |     ACK F7     |              |             |<---------------|              |             |    no RTP      |              |             |                |              |             |  Bob initiates music on hold  |             |                |              |             |                |   REFER Refer-To: A F8             |                |------------->|             |                |    202 F9    |             |                |<-------------|             |                |   NOTIFY F10 |             |                |<-------------|             |                |    200 F11   |             |                |------------->|             |  INVITE F12 Replaces: B       |             |<------------------------------|             |          200 OK F13           |             |------------------------------>|             |           ACK F14             |             |<------------------------------|             |           RTP Music           |             |<==============================|             |     BYE F15    |              |             |--------------->|  NOTIFY F17  |             |  200 OK F16    |<-------------|             |<---------------|  200 OK F18  |             |                |------------->|Johnston, et al.         Best Current Practice                 [Page 38]

RFC 5359                  SIP Service Examples              October 2008             |                |              |             | The music on hold is complete |             |                |              |             |    Bob takes Alice off hold   |             |                |              |             |  INVITE Replaces: M F19       |             |<---------------|              |             |    200 OK F20  |              |             |--------------->|              |             |     ACK F21    |              |             |<---------------|              |             |       RTP      |              |             |<==============>|              |             |            BYE F22            |             |------------------------------>|             |          200 OK F23           |             |<------------------------------|   In this flow, Bob places Alice on hold with music.  This is performed   by Bob sending a REFER to a Music Server that sends an INVITE with   Replaces to Alice.  The Music Server then sends RTP music to Alice.   Bob picks the call up from hold by sending an INVITE with Replaces to   Alice.   Note the use of the rendering feature tag defined inRFC 4235   [RFC4235] used in F5 to indicate that Bob's UA is no longer rendering   media to Bob, i.e., that Bob has placed the call on hold.  Feature   tags are also used in F12 with the automaton (defined inRFC 3840   [RFC3840]) and byeless feature tags (defined inRFC 4235 [RFC4235])   to describe the capabilities of the Music Server.   Should Alice not wish to receive music on hold, her UA could refuse   F12 and she will remain on hold with Bob, but in silence.   Message Details     F1 INVITE Alice -> Bob     INVITE sips:bob@biloxi.example.com SIP/2.0     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74bf9     Max-Forwards: 70     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>     Call-ID: 12345600@atlanta.example.com     CSeq: 1 INVITE     Contact: <sips:a8342043f@atlanta.example.com;gr>     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFYJohnston, et al.         Best Current Practice                 [Page 39]

RFC 5359                  SIP Service Examples              October 2008     Supported: replaces, gruu     Content-Type: application/sdp     Content-Length: ...     v=0     o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com     s=     c=IN IP4 client.atlanta.example.com     t=0 0     m=audio 49170 RTP/AVP 0     a=rtpmap:0 PCMU/8000     F2 180 Ringing Bob -> Alice     SIP/2.0 180 Ringing     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74bf9      ;received=192.0.2.103     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 1 INVITE     Contact: <sips:bob@client.biloxi.example.com>     Content-Length: 0     F3 200 OK Bob -> Alice     SIP/2.0 200 OK     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74bf9      ;received=192.0.2.103     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 1 INVITE     Contact: <sips:bob@client.biloxi.example.com>     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY     Supported: replaces     Content-Type: application/sdp     Content-Length: ...     v=0     o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com     s=     c=IN IP4 client.biloxi.example.com     t=0 0Johnston, et al.         Best Current Practice                 [Page 40]

RFC 5359                  SIP Service Examples              October 2008     m=audio 3456 RTP/AVP 0     a=rtpmap:0 PCMU/8000     F4 ACK Alice -> Bob     ACK sips:bob@client.biloxi.example.com SIP/2.0     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74bfd     Max-Forwards: 70     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 1 ACK     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY     Supported: replaces     Content-Length: 0     /* Bob places Alice on hold. */     F5 INVITE Bob -> Alice     INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bK874bk     To: Alice <sips:alice@atlanta.example.com>;tag=1234567     From: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 712 INVITE     Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY     Supported: replaces     Content-Type: application/sdp     Content-Length: ...     v=0     o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com     s=     c=IN IP4 client.biloxi.example.com     t=0 0     m=audio 3456 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=sendonlyJohnston, et al.         Best Current Practice                 [Page 41]

RFC 5359                  SIP Service Examples              October 2008     F6 200 OK Alice -> Bob     SIP/2.0 200 OK     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bK874bk      ;received=192.0.2.105     To: Alice <sips:alice@atlanta.example.com>;tag=1234567     From: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 712 INVITE     Contact: <sips:a8342043f@atlanta.example.com;gr>     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY     Supported: replaces, gruu     Content-Type: application/sdp     Content-Length: ...     v=0     o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com     s=     c=IN IP4 client.atlanta.example.com     t=0 0     m=audio 49170 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=recvonly     F7 ACK Bob -> Alice     ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bKq874b     To: Alice <sips:alice@atlanta.example.com>;tag=1234567     From: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 712 ACK     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY     Supported: replaces     Content-Length: 0     /* Bob REFERs Music Server to establish session with Alice        which replaces the established session between Alice and Bob. */     F8 REFER Bob -> Music Server     REFER sips:music@server.example.com SIP/2.0     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bKnashds9Johnston, et al.         Best Current Practice                 [Page 42]

RFC 5359                  SIP Service Examples              October 2008     Max-Forwards: 70     From: Bob <sips:bob@biloxi.example.com>;tag=02134     To: Music Server <sips:music@server.example.com>     Call-ID: 4802029847@biloxi.example.com     CSeq: 1 REFER   <allOneLine>     Refer-To: <sips:a8342043f@atlanta.example.com;gr?Replaces=     12345600%40atlanta.example.com%3Bfrom-tag%3D23431     %3Bto-tag%3D1234567&Require=replaces>   </allOneLine>     Referred-By: <sips:bob@biloxi.example.com>     Contact: <sips:bob@client.biloxi.example.com>     Content-Length: 0     F9 202 Accepted Music Server -> Bob     SIP/2.0 202 Accepted     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bKnashds9      ;received=192.0.2.105     From: Bob <sips:bob@biloxi.example.com>;tag=02134     To: Music Server <sips:music@server.example.com>;tag=56323     Call-ID: 4802029847@biloxi.example.com     Contact: <sips:music@server.example.com>     CSeq: 1 REFER     Content-Length: 0     F10 NOTIFY Music Server -> Bob     NOTIFY sips:bob@client.biloxi.example.com SIP/2.0     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74bT6     To: Bob <sips:bob@biloxi.example.com>;tag=02134     Max-Forwards: 70     From: Music Server <sips:music@server.example.com>;tag=56323     Call-ID: 4802029847@biloxi.example.com     CSeq: 1 NOTIFY     Event: refer     Subscription-State: active;expires=60     Contact: <sips:music@server.example.com>     Content-Type: message/sipfrag     Content-Length: ...     SIP/2.0 100 TryingJohnston, et al.         Best Current Practice                 [Page 43]

RFC 5359                  SIP Service Examples              October 2008     F11 200 OK Bob -> Music Server     SIP/2.0 200 OK     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74bT6      ;received=192.0.2.103     To: Bob <sips:bob@biloxi.example.com>;tag=02134     From: Music Server <sips:music@server.example.com>;tag=56323     Call-ID: 4802029847@biloxi.example.com     CSeq: 1 NOTIFY     Content-Length: 0     /* Music Server places call to Alice to replace session        between Alice and Bob. */     F12 INVITE Music Server -> Alice     INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74rf     Max-Forwards: 70     From: <sips:music@server.example.com>;tag=0111     To: <sips:a8342043f@atlanta.example.com;gr>     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 1 INVITE     Referred-By: <sips:bob@biloxi.example.com>     Contact: <sips:music@server.example.com>;automaton      ;+sip.byeless;+sip.rendering="no"     Require: replaces     Replaces: 12345600@atlanta.example.com      ;from-tag=23431;to-tag=1234567     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY     Supported: replaces     Content-Type: application/sdp     Content-Length: ...     v=0     o=MusicServer 2890844576 2890844576 IN IP4 server.example.com     s=     c=IN IP4 server.example.com     t=0 0     m=audio 49170 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=sendonlyJohnston, et al.         Best Current Practice                 [Page 44]

RFC 5359                  SIP Service Examples              October 2008     F13 200 OK Alice -> Music Server     SIP/2.0 200 OK     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74rf      ;received=192.0.2.103     From: <sips:music@server.example.com>;tag=0111     To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 1 INVITE     Contact: <sips:a8342043f@atlanta.example.com;gr>     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY     Supported: replaces, gruu     Content-Type: application/sdp     Content-Length: ...     v=0     o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com     s=     c=IN IP4 client.atlanta.example.com     t=0 0     m=audio 49170 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=recvonly     F14 ACK Music Server -> Alice     ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK7rfF     Max-Forwards: 70     From: <sips:music@server.example.com>;tag=0111     To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 1 ACK     Content-Length: 0     F15 BYE Alice -> Bob     BYE sips:bob@client.biloxi.example.com SIP/2.0     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bKnashds7     Max-Forwards: 70     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.comJohnston, et al.         Best Current Practice                 [Page 45]

RFC 5359                  SIP Service Examples              October 2008     CSeq: 2 BYE     Content-Length: 0     F16 200 OK Bob -> Alice     SIP/2.0 200 OK     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bKnashds7      ;received=192.0.2.105     From: Alice <sips:alice@atlanta.example.com>;tag=1234567     To: Bob <sips:bob@biloxi.example.com>;tag=23431     Call-ID: 12345600@atlanta.example.com     CSeq: 2 BYE     Content-Length: 0     /* Music Server reports success back to Bob by returning        a 200 OK response.  Bob obtains the dialog identifiers        from the headers included in the response. */     F17 NOTIFY Music Server -> Bob     NOTIFY sips:bob@client.biloxi.example.com SIP/2.0     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74bf9     To: Bob <sips:bob@biloxi.example.com>;tag=02134     Max-Forwards: 70     From: Music Server <sips:music@server.example.com>;tag=56323     Call-ID: 4802029847@biloxi.example.com     CSeq: 2 NOTIFY     Event: refer     Subscription-State: terminated;reason=noresource     Contact: <sips:music@server.example.com>     Content-Type: message/sipfrag     Content-Length: ...     SIP/2.0 200 OK     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74rf      ;received=192.0.2.103     From: <sips:music@server.example.com>;tag=0111     To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 1 INVITE     Contact: <sips:a8342043f@atlanta.example.com;gr>Johnston, et al.         Best Current Practice                 [Page 46]

RFC 5359                  SIP Service Examples              October 2008     F18 200 OK Bob -> Music Server     SIP/2.0 200 OK     Via: SIP/2.0/TLS server.example.com:5061      ;branch=z9hG4bK74bf9      ;received=192.0.2.103     To: Bob <sips:bob@biloxi.example.com>;tag=02134     From: Music Server <sips:music@server.example.com>;tag=56323     Call-ID: 4802029847@biloxi.example.com     CSeq: 2 NOTIFY     Content-Length: 0     /* Alice is now parked at the Music Server. */     /* Bob picks up the call by sending an INVITE to Alice, who        replaces the existing session with the Music Server. */     F19 INVITE Bob -> Alice     INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bK74bf9     From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr     To: Alice <sips:a8342043f@atlanta.example.com;gr>     Call-ID: uioewrjk2k2were     CSeq: 42121 INVITE     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,      SUBSCRIBE, NOTIFY     Replaces: a5-75-34-12-76@server.example.com      ;to-tag=098594;from-tag=0111     Contact: <sips:bob@client.biloxi.example.com>     Supported: replaces     Content-Type: application/sdp     Content-Length: ...     v=0     o=bob 2890844631 2890844631 IN IP4 client.biloxi.example.com     s=     c=IN IP4 client.biloxi.example.com     t=0 0     m=audio 3458 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=sendrecvJohnston, et al.         Best Current Practice                 [Page 47]

RFC 5359                  SIP Service Examples              October 2008     F20 200 OK Alice -> Bob     SIP/2.0 200 OK     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bK74bf9      ;received=192.0.2.105     From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr     To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=6654323     Call-ID: uioewrjk2k2were     CSeq: 42121 INVITE     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,      SUBSCRIBE, NOTIFY     Contact: <sips:alice@client.atlanta.example.com>     Supported: replaces     Content-Type: application/sdp     Content-Length: ...     v=0     o=alice 2890844576 2890844576 IN IP4 client.atlanta.example.com     s=     c=IN IP4 client.atlanta.example.com     t=0 0     m=audio 49170 RTP/AVP 0     a=rtpmap:0 PCMU/8000     a=sendrecv     F21 200 ACK Bob -> Alice     ACK sips:alice@client.atlanta.example.com SIP/2.0     Via: SIP/2.0/TLS client.biloxi.example.com:5061      ;branch=z9hG4bKj974bf9     From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr     To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=6654323     Call-ID: uioewrjk2k2were     CSeq: 42121 ACK     Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,      SUBSCRIBE, NOTIFY     Supported: replaces     Content-Length: 0     F22 BYE Alice -> Music Server     BYE sips:music@server.example.com SIP/2.0     Max-Forwards: 70     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74rfJohnston, et al.         Best Current Practice                 [Page 48]

RFC 5359                  SIP Service Examples              October 2008     To: <sips:music@server.example.com>;tag=0111     From: <sips:a8342043f@atlanta.example.com;gr>;tag=098594     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 15 BYE     Content-Length: 0     F23 200 OK Music Server -> Alice     SIP/2.0 200 OK     Via: SIP/2.0/TLS client.atlanta.example.com:5061      ;branch=z9hG4bK74rf      ;received=192.0.2.103     To: <sips:music@server.example.com>;tag=0111     From: <sips:a8342043f@atlanta.example.com;gr>;tag=098594     Call-ID: a5-75-34-12-76@server.example.com     CSeq: 15 BYE     Content-Length: 0     /* Normal media session between Alice and Bob is resumed. */Johnston, et al.         Best Current Practice                 [Page 49]

RFC 5359                  SIP Service Examples              October 20082.4.  Transfer - Unattended          Alice                 Bob                 Carol            |      INVITE F1     |                    |            |<-------------------|                    |            |   180 Ringing F2   |                    |            |------------------->|                    |            |      200 OK F3     |                    |            |------------------->|                    |            |        ACK F4      |                    |            |<-------------------|                    |            |        RTP         |                    |            |<==================>|                    |            |                    |                    |            |  Alice performs unattended transfer     |            |                    |                    |            | REFER Refer-To:C F5|                    |            |------------------->|                    |            |  202 Accepted F6   |                    |            |<-------------------|                    |            |      NOTIFY F7     |                    |            |<-------------------|                    |            |      200 OK F8     |                    |            |------------------->|                    |            |       BYE F9       |                    |            |------------------->|                    |            |     200 OK F10     |                    |            |<-------------------|                    |            |   No RTP Session   | INVITE Referred-By: A F11            |                    |------------------->|            |                    |   180 Ringing F12  |            |                    |<-------------------|            |                    |     200 OK F13     |            |                    |<-------------------|            |                    |       ACK F14      |            |                    |------------------->|            |                    |        RTP         |            |                    |<==================>|            |      NOTIFY F15    |                    |            |<-------------------|                    |            |      200 OK F16    |                    |            |------------------->|                    |            |                    |                    |Johnston, et al.         Best Current Practice                 [Page 50]

RFC 5359                  SIP Service Examples              October 2008   In this scenario, Bob calls Alice.  Alice then transfers Bob to   Carol, then Alice disconnects with Bob.  Bob establishes the session   to Carol then reports the success back to Alice in the NOTIFY in F15.   If the transfer fails, Bob can send a new INVITE back to Alice to re-   establish the session.   Despite the BYE sent by Alice in F9, the dialog between Alice and Bob   still exists until the subscription created by the REFER has   terminated (either due to a NOTIFY containing a Subscription-State:   terminated;reason=noresource header field, as in F15, or a 481   response to a NOTIFY).   For more about call transfer, see the transfer document [TRANSFER].   Message Details      F1 INVITE Bob -> Alice      INVITE sips:alice@atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 180 Ringing Alice -> Bob      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=314159Johnston, et al.         Best Current Practice                 [Page 51]

RFC 5359                  SIP Service Examples              October 2008      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Content-Length: 0      F3 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F4 ACK Bob -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds2      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      /* Session is established between Alice and Bob. */Johnston, et al.         Best Current Practice                 [Page 52]

RFC 5359                  SIP Service Examples              October 2008      /* Alice performs unattended transfer of Bob to Carol. */      F5 REFER Alice -> Bob      REFER sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds8      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 101 REFER      Refer-To: <sips:carol@chicago.example.com>      Referred-By: <alice@atlanta.example.com>      Contact: <sips:alice@client.atlanta.example.com>      Content-Length: 0      F6 202 Accepted Bob -> Alice      SIP/2.0 202 Accepted      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds8       ;received=192.0.2.105      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      Contact: <sips:bob@client.biloxi.example.com>      CSeq: 101 REFER      Content-Length: 0      F7 NOTIFY Bob -> Alice      NOTIFY sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds32      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 NOTIFY      Event: refer      Subscription-State: active;expires=60      Contact: <sips:bob@client.biloxi.example.com>      Content-Type: message/sipfrag      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 53]

RFC 5359                  SIP Service Examples              October 2008      SIP/2.0 100 Trying      F8 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds32       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 2 NOTIFY      Content-Length: 0      /* Alice now disconnects with Bob. */      F9 BYE Alice -> Bob      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds43      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 102 BYE      Content-Length: 0      F10 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds43       ;received=192.0.2.105      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345601@atlanta.example.com      CSeq: 102 BYE      Content-Length: 0      /* Bob attempts the transfer to Carol. */Johnston, et al.         Best Current Practice                 [Page 54]

RFC 5359                  SIP Service Examples              October 2008      F11 INVITE Bob -> Carol      INVITE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds1      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Referred-By: <alice@atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844539 2890844539 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3458 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F12 180 Ringing Carol -> Bob      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds1       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Content-Length: 0      F13 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds1       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287Johnston, et al.         Best Current Practice                 [Page 55]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890944542 2890844542 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F14 ACK Bob -> Carol      ACK sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds9      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287      Call-ID: 7436222@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* Bob and Carol now have established a session.  Bob reports         success to Alice, which Alice probably ignores. */      F15 NOTIFY Bob -> Alice      NOTIFY sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds67      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 3 NOTIFY      Event: refer      Subscription-State: terminated;reason=noresource      Contact: <sips:bob@client.biloxi.example.com>      Content-Type: message/sipfragJohnston, et al.         Best Current Practice                 [Page 56]

RFC 5359                  SIP Service Examples              October 2008      Content-Length: ...      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds1       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Content-Type: application/sdp      Content-Length: ...      F16 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds6       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=314159      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345601@atlanta.example.com      CSeq: 3 NOTIFY      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 57]

RFC 5359                  SIP Service Examples              October 20082.5.  Transfer - Attended           Alice             Bob          Carol             |                |              |             |    INVITE F1   |              |             |--------------->|              |             | 180 Ringing F2 |              |             |<---------------|              |             |    200 OK F3   |              |             |<---------------|              |             |     ACK F4     |              |             |--------------->|              |             |       RTP      |              |             |<==============>|              |             |INVITE (hold) F5|              |             |<---------------|              |             |    200 OK F6   |              |             |--------------->|              |             |     ACK F7     |              |             |<---------------|              |             |     No RTP     |              |             |                |  INVITE F8   |             |                |------------->|             |                | 180 Ringing F9             |                |<-------------|             |                |  200 OK F10  |             |                |<-------------|             |                |    ACK F11   |             |                |------------->|             |                |     RTP      |             |                |<============>|             |                |INVITE (hold) F12             |                |------------->|             |                | 200 OK F13   |             |                |<-------------|             |                |    ACK F14   |             |                |------------->|             |                |     No RTP   |             | REFER Refer-To: C F15         |             |<---------------|              |             |202 Accepted F16|              |             |--------------->|              |             |   NOTIFY F17   |              |             |--------------->|              |             |   200 OK F18   |              |             |<---------------|              |             |     INVITE Replaces: B F19    |             |------------------------------>|Johnston, et al.         Best Current Practice                 [Page 58]

RFC 5359                  SIP Service Examples              October 2008             |            200 OK F20         |             |<------------------------------|             |             ACK F21           |             |------------------------------>|             |               RTP             |             |<=============================>|             |                |    BYE F22   |             |                |<-------------|             |                |  200 OK F23  |             |                |------------->|             |   NOTIFY F24   |              |             |--------------->|              |             |   200 OK F25   |              |             |<---------------|              |             |    BYE F26     |              |             |<---------------|              |             |   200 OK F27   |              |             |--------------->|              |   In this scenario, Alice calls Bob.  Bob puts Alice on hold then calls   Carol to announce transfer, then places Carol on hold.  Bob transfers   Alice to Carol, which replaces the session between Bob and Carol.   Carol then disconnects session with Bob.  Alice reports success of   transfer to Bob, who then disconnects with Alice.  In this example,   the Replaces header field [RFC3891] is inserted into the Refer-To URI   by Bob.  Note that the Refer-To URI is the Contact URI returned by   Carol in the 200 OK response F10.  This ensures that only the correct   instance of Carol is reached.  The presence of the gr URI parameter   in the Contact URI in message F10 indicates that the Contact URI is a   GRUU [GRUU] and will be globally routable outside of the dialog.   Without knowing the Contact URI is a gruu, Bob must be prepared, if   the triggered INVITE had failed, to retry the REFER with a Refer-To   URI of the URI used to reach Carol but with a Require: replaces   header escaped in the Refer-To header field, as discussed in the   transfer document [TRANSFER].   Message Details      F1 INVITE Alice -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.comJohnston, et al.         Best Current Practice                 [Page 59]

RFC 5359                  SIP Service Examples              October 2008      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 180 Ringing Bob -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0      F3 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 60]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F4 ACK Alice -> Bob      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      /* Alice and Bob have established a session.         Bob puts Alice on hold. */      F5 INVITE Bob -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Content-Type: application/sdp      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.comJohnston, et al.         Best Current Practice                 [Page 61]

RFC 5359                  SIP Service Examples              October 2008      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      F6 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F7 ACK Bob -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds3      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 ACK      Content-Length: 0      /* Bob calls Carol. */Johnston, et al.         Best Current Practice                 [Page 62]

RFC 5359                  SIP Service Examples              October 2008      F8 INVITE Bob -> Carol      INVITE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3458 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F9 180 Ringing Carol -> Bob      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 INVITE      Contact: <sips:39itp34klkd@chicago.example.com>      Content-Length: 0      F10 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.comJohnston, et al.         Best Current Practice                 [Page 63]

RFC 5359                  SIP Service Examples              October 2008      CSeq: 42 INVITE      Contact: <sips:39itp34klkd@chicago.example.com;gr>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F11 ACK Bob -> Carol      ACK sips:39itp34klkd@chicago.example.com;gr SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashd5      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 ACK      Content-Length: 0      /* Bob puts Carol on hold. */      F12 INVITE Bob -> Carol      INVITE sips:39itp34klkd@chicago.example.com;gr SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds0      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 43 INVITE      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 64]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=bob 289084834 2890844835 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3458 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=sendonly      F13 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds0       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 43 INVITE      Contact: <sips:39itp34klkd@chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844922 2890844923 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      a=recvonly      F14 ACK Bob -> Carol      ACK sips:39itp34klkd@chicago.example.com;gr SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash334      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.comJohnston, et al.         Best Current Practice                 [Page 65]

RFC 5359                  SIP Service Examples              October 2008      CSeq: 43 ACK      Content-Length: 0      /* Bob transfers Alice to Carol. */      F15 REFER Bob -> Alice      REFER sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds2g      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1025 REFER    <allOneLine>      Refer-To: <sips:39itp34klkd@chicago.example.com?Replaces=      sdjfdjfskdf%40biloxi.example.com%3Bto-tag%3D5f35a3      %3Bfrom-tag%3D8675309&Require=replaces>    </allOneLine>      Referred-By: <sips:bob@biloxi.example.com>      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0      F16 202 Accepted Alice -> Bob      SIP/2.0 202 Accepted      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds2g       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      Contact: <sips:alice@client.atlanta.example.com>      CSeq: 1025 REFER      Content-Length: 0      F17 NOTIFY Alice -> Bob      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfK      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431Johnston, et al.         Best Current Practice                 [Page 66]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345600@atlanta.example.com      CSeq: 2 NOTIFY      Contact: <sips:alice@client.atlanta.example.com>      Event: refer      Subscription-State: active;expires=60      Content-Type: message/sipfrag      Content-Length: ...      SIP/2.0 100 Trying      F18 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfK       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 2 NOTIFY      Content-Length: 0      /* Alice establishes session with Carol, which replaces the         session between Bob and Carol. */      F19 INVITE Alice -> Carol      INVITE sips:39itp34klkd@chicago.example.com;gr SIP/2.0      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKadfe4ko      To: Carol <sips:39itp34klkd@chicago.example.com>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=3461      Call-ID: 9435674543@atlanta.example.com      CSeq: 1 INVITE      Require: replaces      Referred-By: <sips:bob@biloxi.example.com>      Replaces: sdjfdjfskdf@biloxi.example.com       ;to-tag=5f35a3;from-tag=8675309      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                 [Page 67]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=alice 2890844989 2890844989 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 3458 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F20 200 OK Carol -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKadfe4ko       ;received=192.0.2.103      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a      From: Alice <sips:alice@atlanta.example.com>;tag=3461      Call-ID: 9435674543@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:39itp34klkd@chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844221 2890844221 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 49172 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F21 ACK Alice -> Carol      ACK sips:39itp34klkd@chicago.example.com;gr SIP/2.0      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKadfe4kU3      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=3461      Call-ID: 9435674543@atlanta.example.com      CSeq: 1 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFYJohnston, et al.         Best Current Practice                 [Page 68]

RFC 5359                  SIP Service Examples              October 2008      Supported: replaces      Content-Length: 0      /* Carol then disconnects from Bob. */      F22 BYE Carol -> Bob      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfE      To: Bob <sips:bob@biloxi.example.com>;tag=8675309      Max-Forwards: 70      From: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 1 BYE      Content-Length: 0      F23 200 OK Bob -> Carol      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfE       ;received=192.0.2.123      To: Bob <sips:bob@biloxi.example.com>;tag=8675309      From: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 1 BYE      Content-Length: 0      /* Alice tells Bob that the call has been         successfully transferred. */      F24 NOTIFY Alice -> Bob      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf2N      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 3 NOTIFY      Event: refer      Subscription-State: terminated;reason=noresourceJohnston, et al.         Best Current Practice                 [Page 69]

RFC 5359                  SIP Service Examples              October 2008      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: message/sipfrag      Content-Length: ...      SIP/2.0 200 OK      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKadfe4ko       ;received=192.0.2.103      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a      From: Alice <sips:alice@atlanta.example.com>;tag=3461      Call-ID: 9435674543@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:39itp34klkd@chicago.example.com>      F25 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 3 NOTIFY      Content-Length: 0      /* Bob disconnects with Alice. */      F26 BYE Bob -> Alice      BYE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7P      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1026 BYE      Content-Length: 0      F27 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7PJohnston, et al.         Best Current Practice                 [Page 70]

RFC 5359                  SIP Service Examples              October 2008       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1026 BYE      Content-Length: 02.6.  Transfer - Instant Messaging            Alice          Bob                Carol             |              |                   |             |   INVITE F1  |                   |             |------------->|                   |             | 180 Ringing F2                   |             |<-------------|                   |             |  200 OK F3   |                   |             |<-------------|                   |             |    ACK F4    |                   |             |------------->|                   |             |  Both way RTP Established        |             |<============>|                   |             |              |     MESSAGE F5    |             |              |------------------>|             |              |     200 OK F6     |             |              |<------------------|             |              |                   |             |       INVITE Replaces:A-B F7     |             |<---------------------------------|             |            200 OK F8             |             |--------------------------------->|             |               ACK F9             |             |<---------------------------------|             |   Both way RTP Established       |             |<================================>|             |    BYE F10   |                   |             |------------->|                   |             |  200 OK F11  |                   |             |<-------------|                   |             |                                  |   In this scenario, Alice and Bob establish a session between them.   Bob wants Carol to take the call and so sends an Instant Message (IM)   to Carol containing Alice's URI and an embedded Replaces header   field.  If Carol clicks on the URI, Carol's SIP UA sends an INVITE to   Alice, which replaces the session with Bob.Johnston, et al.         Best Current Practice                 [Page 71]

RFC 5359                  SIP Service Examples              October 2008   This scenario shows the use of the SIP MESSAGE [RFC3428] method to   pass the URI.  However, another IM protocol or other method could   have been used to pass the URI from Bob to Carol.   Message Details      F1 INVITE Alice -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:a8342043f@atlanta.example.com;gr>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 180 Ringing Bob -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 72]

RFC 5359                  SIP Service Examples              October 2008      F3 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      Contact: <sips:bob@client.biloxi.example.com>      CSeq: 1 INVITE      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F4 ACK Alice -> Bob      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74r      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      CSeq: 1 ACK      Content-Length: 0      /* Bob IMs Carol. */      F5 MESSAGE Bob -> Carol      MESSAGE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash      Max-Forwards: 70Johnston, et al.         Best Current Practice                 [Page 73]

RFC 5359                  SIP Service Examples              October 2008      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 MESSAGE      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE      Supported: replaces      Content-Type: text/html      Content-Length: ...      <HTML>Do you want to take this call from    <allOneLine>      <A HREF="sips:a8342043f@atlanta.example.com;gr?Replaces=      12345600@atlanta.example.com%3Bto-tag%3D3145678      %3Bfrom-tag%3D1234567&Require=replaces">      Alice</A>?    </allOneLine>       </HTML>      F6 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 MESSAGE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE      Supported: replaces      Content-Length: 0      /* Carol takes the call from Bob. */      F7 INVITE  Carol -> Alice      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0      Via: SIP/2.0/TLS pc.biloxi.example.com:5061       ;branch=z9hG4bK74HH      Max-Forwards: 70      From: Carol <sips:carol@chicago.example.com>;tag=8675310      To: Alice <sips:a8342043f@atlanta.example.com;gr>      Call-ID: 563456212@b2.chicago.example.com      CSeq: 1 INVITE      Require: replacesJohnston, et al.         Best Current Practice                 [Page 74]

RFC 5359                  SIP Service Examples              October 2008      Replaces: 12345600@atlanta.example.com       ;to-tag=3145678;from-tag=1234567      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890843122 2890843122 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 5342 RTP/AVP 0      a=rtpmap:0 PCMU/8000      /* Alice matches the dialog information in the         Replaces header and accepts the INVITE. */      F8 200 OK Alice -> Carol      SIP/2.0 200 OK      Via: SIP/2.0/TLS pc.biloxi.example.com:5061       ;branch=z9hG4bK74HH       ;received=192.0.2.114      From: Carol <sips:carol@chicago.example.com>;tag=8675310      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=131256      Call-ID: 563456212@b2.chicago.example.com      CSeq: 1 INVITE      Contact: <sips:a8342043f@atlanta.example.com;gr>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 289084543 289084543 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49172 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 75]

RFC 5359                  SIP Service Examples              October 2008      F9 ACK  Carol -> Alice      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0      Via: SIP/2.0/TLS b2.biloxi.example.com:5061       ;branch=z9hG4bK7435      Max-Forwards: 70      From: Carol <sips:carol@chicago.example.com>;tag=8675310      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=131256      Call-ID: 563456212@b2.chicago.example.com      CSeq: 1 ACK      Content-Length: 0      /* RTP streams are established between Alice and Carol.         Alice hangs up with Bob due to the Replaces header field. */      F10 BYE Alice -> Bob      BYE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F11 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq:  2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 76]

RFC 5359                  SIP Service Examples              October 20082.7.  Call Forwarding Unconditional            Alice           Proxy          Gateway             |                |              |             |    INVITE F1   |              |             |--------------->|              |             |(100 Trying) F2 |              |             |<---------------|              |             | (181 Call Is Being Forwarded) F3             |<---------------|   INVITE F4  |             |                |------------->|             |                |180 Ringing F5|             | 180 Ringing F6 |<-------------|             |<---------------|  200 OK F7   |             |    200 OK F8   |<-------------|             |<---------------|              |             |     ACK F9     |              |             |--------------->|    ACK F10   |             |                |------------->|             |    Both way RTP Established   |             |<=============================>|             |     BYE F11    |              |             |--------------->|   BYE F12    |             |                |------------->|             |                |   200 OK F13 |             |    200 OK F14  |<-------------|             |<---------------|              |             |                |              |   Bob wants all calls forwarded to the Public Switched Telephone   Network (PSTN) (which is just another URI to the proxy server).   Alice calls Bob.  The proxy server rewrites the Request URI, and   forwards the INVITE to a Gateway.  Details of messaging behind the   Gateway are not shown.   Note that the 181 Call is Being Forwarded response is shown as sent   by the proxy.  Strictly speaking, the proxy is behaving as a user   agent in this case as a proxy cannot generate non-100 provisional   responses.   Note also that forwarding could be accomplished using a redirect (302   Moved Temporarily response).Johnston, et al.         Best Current Practice                 [Page 77]

RFC 5359                  SIP Service Examples              October 2008   Message Details      F1 INVITE Alice -> Proxy      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 (100 Trying) Proxy -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F3 (181 Call is Being Forwarded) Proxy -> Alice      SIP/2.0 181 Call is Being Forwarded      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=9214dJohnston, et al.         Best Current Practice                 [Page 78]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      /* Proxy forwards call by rewriting Request-URI. */      F4 INVITE Proxy -> Gateway      INVITE sips:+19727293660@gw1.example.com;user=phone SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F5 180 Ringing Gateway -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.comJohnston, et al.         Best Current Practice                 [Page 79]

RFC 5359                  SIP Service Examples              October 2008      CSeq: 1 INVITE      Contact: <sips:+19727293660@gw1.example.com;user=phone>      Content Length:0      F6 180 Ringing Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:+19727293660@gw1.example.com;user=phone>      Content Length: 0      F7 200 OK Gateway -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:+19727293660@gw1.example.com;user=phone>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=GATEWAY1 2890844527 2890844527 IN IP4 gatewayone.example.com      s=      c=IN IP4 gatewayone.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 80]

RFC 5359                  SIP Service Examples              October 2008      F8 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:+19727293660@gw1.example.com;user=phone>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=GATEWAY1 2890844527 2890844527 IN IP4 gatewayone.example.com      s=      c=IN IP4 gatewayone.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F9 ACK Alice -> Proxy      ACK sips:+19727293660@gw1.example.com;user=phone SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf31      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F10 ACK Proxy -> Gateway      ACK sips:+19727293660@gw1.example.com;user=phone SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749ws.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf31       ;received=192.0.2.103      Max-Forwards: 69Johnston, et al.         Best Current Practice                 [Page 81]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F11 BYE Alice -> Proxy      BYE sips:+19727293660@gw1.example.com;user=phone SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfJe      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F12 BYE Proxy -> Gateway      BYE sips:+19727293660@gw1.example.com;user=phone SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749G1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfJe       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F13 200 OK Gateway -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749G1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfJe       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159Johnston, et al.         Best Current Practice                 [Page 82]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F14 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfJe       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 12345600@atlanta.example.com      CSeq:  2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 83]

RFC 5359                  SIP Service Examples              October 20082.8.  Call Forwarding - Busy           Alice            Proxy          User B1             User B2             |                |              |                   |             |    INVITE F1   |              |                   |             |--------------->|   INVITE F2  |                   |             |                |------------->|                   |             |(100 Trying) F3 |              |                   |             |<---------------|  486 Busy F4 |                   |             |                |<-------------|                   |             |                |     ACK F5   |                   |             |                |------------->|                   |             |(181 Call is Being Forwarded) F6                   |             |<---------------|              |    INVITE F7      |             |                |--------------------------------->|             |                |              | 180 Ringing F8    |             |                |<---------------------------------|             | 180 Ringing F9 |              |                   |             |<---------------|              |      200 OK F10   |             |                |<---------------------------------|             |    200 OK F11  |              |                   |             |<---------------|              |                   |             |     ACK F12    |              |                   |             |--------------->|              |     ACK F13       |             |                |--------------------------------->|             |               Both way RTP Established            |             |<=================================================>|             |    BYE F14     |              |                   |             |--------------->|              |      BYE F15      |             |                |--------------------------------->|             |                |              |    200 OK F16     |             |  200 OK F17    |<---------------------------------|             |<---------------|              |                   |             |                |              |                   |   Bob wants calls to B1 forwarded to B2 if B1 is busy (this information   is known to the proxy).  Alice calls B1, B1 is busy, the proxy server   places call to B2.   Message Details      F1 INVITE Alice -> Proxy      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70Johnston, et al.         Best Current Practice                 [Page 84]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 INVITE Proxy -> B1      INVITE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 85]

RFC 5359                  SIP Service Examples              October 2008      F3 (100 Trying) Proxy -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F4 486 Busy Here B1 -> Proxy      SIP/2.0 486 Busy Here      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F5 ACK Proxy -> B1      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F6 (181 Call is Being Forwarded) Proxy -> Alice      SIP/2.0 181 Call is Being Forwarded      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103Johnston, et al.         Best Current Practice                 [Page 86]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=9214d      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      /* The proxy now forwards the call to B2. */      F7 INVITE Proxy -> B2      INVITE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F8 180 Ringing B2 -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567Johnston, et al.         Best Current Practice                 [Page 87]

RFC 5359                  SIP Service Examples              October 2008      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Content-Length: 0      F9 180 Ringing Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Content-Length: 0      F10 200 OK B2 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com      s=      c=IN IP4 client2.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                 [Page 88]

RFC 5359                  SIP Service Examples              October 2008      F11 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com      s=      c=IN IP4 client2.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F12 ACK Alice -> Proxy      ACK sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfX      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F13 ACK Proxy -> B2      ACK sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83731      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfX       ;received=192.0.2.103      Max-Forwards: 69Johnston, et al.         Best Current Practice                 [Page 89]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* RTP streams are established between Alice and B2. */      /* Alice eventually hangs up with User B2. */      F14 BYE Alice -> Proxy      BYE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bW4      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F15 BYE Proxy -> B2      BYE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837493      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bW4       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F16 200 OK B2 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837493       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061Johnston, et al.         Best Current Practice                 [Page 90]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bK74bW4       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F17 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bW4       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq:  2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 91]

RFC 5359                  SIP Service Examples              October 20082.9.  Call Forwarding - No Answer           Alice            Proxy         User B1             User B2             |                |              |                   |             |    INVITE F1   |              |                   |             |--------------->|   INVITE F2  |                   |             |(100 Trying) F3 |------------->|                   |             |<---------------|180 Ringing F4|                   |             | 180 Ringing F5 |<-------------|                   |             |<---------------|              |                   |             |                 Request Timeout                   |             |                |              |                   |             |                |   CANCEL F6  |                   |             |                |------------->|                   |             |                |   200 OK F7  |                   |             |                |<-------------|                   |             |                |     487 F8   |                   |             |                |<-------------|                   |             |                |     ACK F9   |                   |             |                |------------->|                   |             |(181 Call is Being Forwarded) F10                  |             |<---------------|              |    INVITE F11     |             |                |--------------------------------->|             |                |              | 180 Ringing F12   |             | 180 Ringing F13|<---------------------------------|             |<---------------|              |      200 OK F14   |             |                |<---------------------------------|             |   200 OK F15   |              |                   |             |<---------------|              |                   |             |     ACK F16    |              |                   |             |--------------->|              |     ACK F17       |             |                |--------------------------------->|             |               Both way RTP Established            |             |<=================================================>|             |    BYE F18     |              |                   |             |--------------->|              |      BYE F19      |             |                |--------------------------------->|             |                |              |    200 OK F20     |             |  200 OK F21    |<---------------------------------|             |<---------------|              |                   |             |                |              |                   |   Bob wants calls to B1 forwarded to B2 if B1 is not answered   (information is known to the proxy server).  Alice calls B1 and no   one answers.  The proxy server then places the call to B2.Johnston, et al.         Best Current Practice                 [Page 92]

RFC 5359                  SIP Service Examples              October 2008   Message Details      F1 INVITE Alice -> Proxy      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 INVITE Proxy -> B1      INVITE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=Johnston, et al.         Best Current Practice                 [Page 93]

RFC 5359                  SIP Service Examples              October 2008      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F3 (100 Trying) Proxy -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F4 180 Ringing B1 -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0      F5 180 Ringing Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITEJohnston, et al.         Best Current Practice                 [Page 94]

RFC 5359                  SIP Service Examples              October 2008      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0      /* B1 rings until a configurable timer expires in the proxy.  The         proxy sends Cancel and proceeds down the list of routes. */      F6 CANCEL Proxy -> B1      CANCEL sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 CANCEL      Content-Length: 0      F7 200 OK B1 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=329d823      Call-ID: 12345600@atlanta.example.com      CSeq: 1 CANCEL      Content-Length: 0      F8 487 Request Terminated B1 -> Proxy      SIP/2.0 487 Request Terminated      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0Johnston, et al.         Best Current Practice                 [Page 95]

RFC 5359                  SIP Service Examples              October 2008      F9 ACK Proxy -> B1      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=3145678      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F10 (181 Call is Being Forwarded) Proxy -> Alice      SIP/2.0 181 Call is Being Forwarded      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=9214d      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F11 INVITE Proxy -> B2      INVITE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=Johnston, et al.         Best Current Practice                 [Page 96]

RFC 5359                  SIP Service Examples              October 2008      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F12 180 Ringing B2 -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Content-Length: 0      F13 180 Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Content-Length: 0      F14 200 OK B2 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103Johnston, et al.         Best Current Practice                 [Page 97]

RFC 5359                  SIP Service Examples              October 2008      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com      s=      c=IN IP4 client2.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F15 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client2.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com      s=      c=IN IP4 client2.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F16 ACK Alice -> Proxy      ACK sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061Johnston, et al.         Best Current Practice                 [Page 98]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bK74bf3      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F17 ACK Proxy -> B2      ACK sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8374.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf3       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* RTP streams are established between Alice and B2.         Alice hangs up with User B2. */      F18 BYE Alice -> Proxy      BYE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b3f      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F19 BYE Proxy -> B2      BYE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837.1Johnston, et al.         Best Current Practice                 [Page 99]

RFC 5359                  SIP Service Examples              October 2008      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b3f       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F20 200 OK B2 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK837.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b3f       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 2 BYE      Content-Length: 0      F21 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b3f       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq:  2 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 100]

RFC 5359                  SIP Service Examples              October 20082.10.  3-Way Conference - Third Party Is Added            Alice           Bob            Carol             |    INVITE F1   |              |             |--------------->|              |             | 180 Ringing F2 |              |             |<---------------|              |             |    200 OK F3   |              |             |<---------------|              |             |     ACK F4     |              |             |--------------->|              |             |       RTP      |              |             |<==============>|              |             |   INVITE F5    |              |             |<---------------|              |             |    200 OK F6   |              |             |--------------->|              |             |     ACK F7     |              |             |<---------------|  INVITE F8   |             |                |------------->|             |                |    180 F9    |             |                |<-------------|             |                |  200 OK F10  |             |                |<-------------|             |                |  ACK F11     |             |                |------------->|             |                |       RTP    |             |                |<============>|   In this scenario, Alice and Bob are in a 2-party call (session) when   Bob wishes to add Carol into the conversation.  Bob is capable of   media mixing in a 3-party call.  Bob first sends a re-INVITE to   Alice, changing Contact URIs to one that indicates Bob's mixer and   acts like a focus.  As a result, Bob includes the "isfocus" feature   tag [RFC3840] as described in [RFC4579].  Bob then INVITEs Carol   using the same Contact URI.  Note that Bob could wait to re-INVITE   Alice until after Carol has answered.  Bob could also put Alice on   hold before calling Carol.   Message Details      F1 INVITE Alice -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9Johnston, et al.         Best Current Practice                [Page 101]

RFC 5359                  SIP Service Examples              October 2008      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 180 Ringing Bob -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:b54gh42f5@biloxi.example.com>      Content-Length: 0      F3 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:b54gh42f5@biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFYJohnston, et al.         Best Current Practice                [Page 102]

RFC 5359                  SIP Service Examples              October 2008      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F4 ACK Alice -> Bob      ACK sips:b54gh42f5@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfL      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* Alice and Bob have established a session.         Bob re-INVITEs, changing Contact URIs. */      F5 INVITE Bob -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus      Content-Type: application/sdp      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=Johnston, et al.         Best Current Practice                [Page 103]

RFC 5359                  SIP Service Examples              October 2008      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 49172 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F6 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F7 ACK Bob -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash3G      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 ACK      Content-Length: 0      /* Bob calls Carol. */Johnston, et al.         Best Current Practice                [Page 104]

RFC 5359                  SIP Service Examples              October 2008      F8 INVITE Bob -> Carol      INVITE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashJfd      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 INVITE      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 48174 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F9 180 Ringing Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashJfd       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=341313      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F10 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashJfd       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309Johnston, et al.         Best Current Practice                [Page 105]

RFC 5359                  SIP Service Examples              October 2008      To: Carol <sips:carol@chicago.example.com>;tag=341313      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F11 ACK Bob -> Carol      ACK sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash431      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=341313      Call-ID: sdjfdjfskdf@biloxi.example.com      CSeq: 42 ACK      Content-Length: 0      /* Bob's mixer now mixes media from both Alice and Carol         to create the 3-way conference. */Johnston, et al.         Best Current Practice                [Page 106]

RFC 5359                  SIP Service Examples              October 20082.11.  3-Way Conference - Third Party Joins            Alice           Bob            Carol             |    INVITE F1   |              |             |--------------->|              |             | 180 Ringing F2 |              |             |<---------------|              |             |    200 OK F3   |              |             |<---------------|              |             |     ACK F4     |              |             |--------------->|              |             |       RTP      |              |             |<==============>|  INVITE Join:A-B F5             |                |<-------------|             |                |    180 F6    |             |                |------------->|             |   INVITE F7    |              |             |<---------------|              |             |    200 OK F8   |              |             |--------------->|              |             |     ACK F9     |              |             |<---------------|              |             |                |  200 OK F10  |             |                |------------->|             |                |  ACK F11     |             |                |<-------------|             |                |       RTP    |             |                |<============>|   In this scenario, Alice and Bob are in a 2-party call and Carol   wishes to join, resulting in a 3-party call.  Carol could have   learned Bob's dialog identifier using some non-SIP means, or possibly   from a NOTIFY with the dialog package sent by Bob.  Carol sends an   INVITE to Bob containing a Join header identifying the dialog between   Alice and Bob.  Bob re-INVITEs Alice to switch to focus mode and   includes the "isfocus" feature tag [RFC3840] as described in   [RFC4579].  Bob then accepts the INVITE from Carol, resulting in the   3-way call.   Message Details      F1 INVITE Alice -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9Johnston, et al.         Best Current Practice                [Page 107]

RFC 5359                  SIP Service Examples              October 2008      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 180 Ringing Bob -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:b54gh42f5@biloxi.example.com>      Content-Length: 0      F3 200 OK Bob -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:b54gh42f5@biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFYJohnston, et al.         Best Current Practice                [Page 108]

RFC 5359                  SIP Service Examples              October 2008      Supported: replaces, join, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F4 ACK Alice -> Bob      ACK sips:b54gh42f5@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf6      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=23431      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* Alice and Bob have established a session.         Carol requests to join the session. */      F5 INVITE Carol -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKnashds7      Max-Forwards: 70      From: Carol <sips:carol@chicago.example.com>;tag=8675309      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 452k499sk@chicago.example.com      CSeq: 99 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, join      Join: 12345600@atlanta.example.com;from-tag=1234567;to-tag=23431      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                [Page 109]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F6 180 Ringing Bob -> Carol      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKnashds7       ;received=120.      From: Carol <sips:carol@chicago.example.com>;tag=8675309      To: Bob <sips:bob@biloxi.example.com>;tag=0982      Call-ID: 452k499sk@chicago.example.com      CSeq: 99 INVITE      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Length: 0      F7 INVITE Bob -> Alice      INVITE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdyKL      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus      Content-Type: application/sdp      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, join, gruu      Content-Length: ...      v=0      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 49172 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                [Page 110]

RFC 5359                  SIP Service Examples              October 2008      F8 200 OK Alice -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdyKL       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F9 ACK Bob -> Alice      ACK sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnash3g      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=23431      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1024 ACK      Content-Length: 0      F10 200 OK Bob -> Carol      SIP/2.0 200 OK      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKnashds7       ;received=120.      From: Carol <sips:carol@chicago.example.com>;tag=8675309      To: Bob <sips:bob@biloxi.example.com>;tag=0982      Call-ID: 452k499sk@chicago.example.com      CSeq: 99 INVITE      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocusJohnston, et al.         Best Current Practice                [Page 111]

RFC 5359                  SIP Service Examples              October 2008      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, join, gruu      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 48174 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F11 ACK OK Carol -> Bob      ACK sips:bob-Mixer@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS chicago.example.com:5061       ;branch=z9hG4bKnash4Gf      Max-Forwards: 70      From: Carol <sips:carol@chicago.example.com>;tag=8675309      To: Bob <sips:bob@biloxi.example.com>;tag=0982      Call-ID: 452k499sk@chicago.example.com      CSeq: 99 ACK      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces, join      Content-Length:0Johnston, et al.         Best Current Practice                [Page 112]

RFC 5359                  SIP Service Examples              October 20082.12.  Find-Me             Alice           Proxy           User   User   User   User                                              B1     B2     B3     B4             |                |              |      |      |      |             |    INVITE F1   |              |      |      |      |             |--------------->|   INVITE F2  |      |      |      |             |                |------------->|      |      |      |             |(100 Trying) F3 |              |      |      |      |             |<---------------|180 Ringing F4|      |      |      |             |                |<-------------|      |      |      |             | 180 Ringing F5 |              |      |      |      |             |<---------------|              |      |      |      |             |                |    Timeout   |      |      |      |             |                |              |      |      |      |             |                |   CANCEL F6  |      |      |      |             |                |------------->|      |      |      |             |                |   200 OK F7  |      |      |      |             |                |<-------------|      |      |      |             |                |     487 F8   |      |      |      |             |                |<-------------|      |      |      |             |                |     ACK F9   |      |      |      |             |                |------------->|      |      |      |             |                |     INVITE F10      |      |      |             |                |-------------------->|      |      |             |                |480 Not Logged In F11|      |      |             |                |<--------------------|      |      |             |                |              ACK F12|      |      |             |                |-------------------->|      |      |             |                |          INVITE F13        |      |             |                |--------------------------->|      |             |                |      486 Busy Here F14     |      |             |                |<---------------------------|      |             |                |            ACK F15         |      |             |                |--------------------------->|      |             |                |              INVITE F16           |             |                |---------------------------------->|             |                |            180 Ringing F17        |             |     180 F18    |<----------------------------------|             |<---------------|               200 OK F19          |             |   200 OK F20   |<----------------------------------|             |<---------------|                                   |             |     ACK F21    |                                   |             |--------------->|                 ACK F22           |             |                |---------------------------------->|             |               Both way RTP Established             |             |<==================================================>|Johnston, et al.         Best Current Practice                [Page 113]

RFC 5359                  SIP Service Examples              October 2008             |                |                  BYE F23          |             |     BYE F24    |<----------------------------------|             |<---------------|                                   |             |    200 OK F25  |                                   |             |--------------->|                 200 OK F26        |             |                |---------------------------------->|             |                |                                   |   Alice's call to Bob will result in an attempt to locate Bob by   calling locations from a list of contacts.  The location to answer   the call becomes the active set; no other sets may join the call.   While this flow shows a sequential search, the search could be   accomplished using parallel forking.   Message Details      F1 INVITE Alice -> Proxy      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t= 0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F2 INVITE Proxy -> B1      INVITE sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103Johnston, et al.         Best Current Practice                [Page 114]

RFC 5359                  SIP Service Examples              October 2008      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t= 0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F3 (100 Trying) Proxy -> Alice      SIP/2.0 100 Trying      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F4 180 Ringing B1 -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 115]

RFC 5359                  SIP Service Examples              October 2008      F5 180 Ringing Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Content-Length: 0      /* B1 rings until a configurable timer in the proxy         expires.  The proxy then sends Cancel and proceeds down         the list of routes. */      F6 CANCEL Proxy -> B1      CANCEL sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 CANCEL      Content-Length: 0      F7 200 OK B1 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 CANCEL      Content-Length: 0      F8 487 Request Terminated B1 -> Proxy      SIP/2.0 487 Request TerminatedJohnston, et al.         Best Current Practice                [Page 116]

RFC 5359                  SIP Service Examples              October 2008      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F9 ACK Proxy -> B1      ACK sips:bob@client.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.1      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=765432      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F10 INVITE Proxy -> B2      INVITE sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.comJohnston, et al.         Best Current Practice                [Page 117]

RFC 5359                  SIP Service Examples              October 2008      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F11 480 Not Logged In B2 -> Proxy      SIP/2.0 480 Not Logged In      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314756      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F12 ACK Proxy -> B2      ACK sips:bob@client2.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.2      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314756      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F13 INVITE Proxy -> B3      INVITE sips:bob@client3.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.3      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITEJohnston, et al.         Best Current Practice                [Page 118]

RFC 5359                  SIP Service Examples              October 2008      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F14 486 Busy Here B3 -> Proxy      SIP/2.0 486 Busy Here      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.3       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Content-Length: 0      F15 ACK Proxy -> B3      ACK sips:bob@client3.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.3      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7654321      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F16 INVITE Proxy -> B4      INVITE sips:bob@client4.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.4      Via: SIP/2.0/TLS client.atlanta.example.com:5061Johnston, et al.         Best Current Practice                [Page 119]

RFC 5359                  SIP Service Examples              October 2008       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F17 180 Ringing B4 -> Proxy      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.4       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client4.biloxi.example.com>      Content-Length: 0      F18 180 Ringing Proxy -> Alice      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136Johnston, et al.         Best Current Practice                [Page 120]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client4.biloxi.example.com>      Content-Length: 0      F19 200 OK B4 -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83749.4       ;received=192.0.2.54      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client4.biloxi.example.com>      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com      s=      c=IN IP4 client4.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F20 200 OK Proxy -> Alice      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      Record-Route: <sips:ss1.example.com;lr>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client4.biloxi.example.com>      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                [Page 121]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com      s=      c=IN IP4 client4.biloxi.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F21 ACK Alice -> Proxy      ACK sips:bob@client4.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      F22 ACK Proxy -> B4      ACK sips:bob@client4.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK8374      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf       ;received=192.0.2.103      Max-Forwards: 69      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7137136      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* RTP streams are established between Alice and B4. */      /* User B4 hangs up with Alice. */      F23 BYE B4 -> Proxy      BYE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS client4.biloxi.example.com:5061       ;branch=z9hG4bKnashds7Johnston, et al.         Best Current Practice                [Page 122]

RFC 5359                  SIP Service Examples              October 2008      Route: <sips:ss1.example.com;lr>      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=7137136      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 BYE      Content-Length: 0      F24 BYE Proxy -> Alice      BYE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83754      Via: SIP/2.0/TLS client4.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      Max-Forwards: 69      From: Bob <sips:bob@biloxi.example.com>;tag=7137136      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 BYE      Content-Length: 0      F25 200 OK Alice -> Proxy      SIP/2.0 200 OK      Via: SIP/2.0/TLS ss1.example.com:5061       ;branch=z9hG4bK83754       ;received=192.0.2.54      Via: SIP/2.0/TLS client4.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      From: Bob <sips:bob@biloxi.example.com>;tag=7137136      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 BYE      Content-Length: 0      F26 200 OK Proxy -> B4      SIP/2.0 200 OK      Via: SIP/2.0/TLS client4.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.105      From: Bob <sips:bob@biloxi.example.com>;tag=7137136Johnston, et al.         Best Current Practice                [Page 123]

RFC 5359                  SIP Service Examples              October 2008      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 1 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 124]

RFC 5359                  SIP Service Examples              October 20082.13.  Call Management (Incoming Call Screening)                                                      Announcement           Alice           Proxy            Bob           Server             |                |              |              |             |    INVITE F1   |              |              |             |------------------------------>|              |             | 305 Use Proxy F2              |              |             |<------------------------------|              |             |     ACK F3     |              |              |             |------------------------------>|              |             |    INVITE F4   |              |              |             |--------------->|              |              |             | 407 Proxy Authentication F5   |              |             |<---------------|              |              |             |     ACK F6     |              |              |             |--------------->|              |              |             |    INVITE F7   |              |              |             |--------------->|              |              |             | 403 Screening Failure (Terminating) Error-Info: URI F8             |<---------------|              |              |             |     ACK F9     |              |              |             |--------------->|              |              |             |    INVITE F10  |              |              |             |--------------------------------------------->|             |    200 OK F11  |              |              |             |--------------------------------------------->|             |     ACK F12    |                             |             |--------------------------------------------->|             |          Announcement Played to Caller       |             |<=============================================|             |                                    BYE F13   |             |<---------------------------------------------|             |     200 OK F14                               |             |--------------------------------------------->|             |                                              |             |                                              |             |                                              |   Bob has an incoming call screening list; Alice is included on the   list of addresses from which Bob will not accept calls.  Alice   attempts to call Bob.  Messages F1, F2, and F3 are included to show   that Bob does not accept INVITEs that have not been screened by the   proxy.   Note that call screening cannot be done using the From header --   instead some form of authentication credentials must be used.Johnston, et al.         Best Current Practice                [Page 125]

RFC 5359                  SIP Service Examples              October 2008   The screening proxy inserts an announcement URI in an Error-Info   header field, which Alice accesses by sending an INVITE to listen to   the Announcement.  The Announcement Server uses the automaton and   rendering feature tags in F12 and F13 to indicate that it is a media   server only capable of playing announcements.   Message Details      F1 INVITE Alice -> Bob      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      /* Bob only accepts INVITEs that have been screened         by the proxy. */      F2 305 Use Proxy Bob -> Alice      SIP/2.0 305 Use Proxy      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=342123      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:ss1.example.com>      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 126]

RFC 5359                  SIP Service Examples              October 2008      F3 ACK Alice -> Bob      ACK sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=342123      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* A retries the call through the proxy. */      F4 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf0      Max-Forwards: 70      Route: <sips:ss1.example.com>      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      /* Proxy 1 challenges Alice for authentication. */      F5 407 Proxy Authentication Required Proxy 1 -> Alice      SIP/2.0 407 Proxy Authentication Required      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf0       ;received=192.0.2.103Johnston, et al.         Best Current Practice                [Page 127]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7886765      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Proxy-Authenticate: Digest realm="example.com",         nonce="ea9c8e88df84f1cec4341ae6cbe5a359",         qop="auth", nc=00000001, cnonce="0a4f113b",         opaque="", stale=FALSE, algorithm=MD5      Content-Length: 0      F6 ACK Alice -> Proxy 1      ACK sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf0      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=7886765      Call-ID: 12345600@atlanta.example.com      CSeq: 2 ACK      Content-Length: 0      /* Alice responds by sending an INVITE with authentication         credentials in it. */      F7 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf2      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 3 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Proxy-Authorization: Digest username="alice",         realm="example.com", qop=auth,         nc=00000001, cnonce="4gr84543ft2",         nonce="ae9137be1c87d175c2dd63302a0d6e0a",         opaque="", uri="sips:bob@biloxi.example.com",         response="bbaec39f943bdcb3620d90afc548a45c"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...Johnston, et al.         Best Current Practice                [Page 128]

RFC 5359                  SIP Service Examples              October 2008      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F8 403 Screening Failure (Terminating) Proxy 1 -> Alice      SIP/2.0 403 Screening Failure (Terminating)      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf2       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=ffe254      Call-ID: 12345600@atlanta.example.com      CSeq: 3 INVITE      Error-Info: <sips:screen-fail-term-ann@ms.biloxi.example.com>      Content-Length: 0      F9 ACK Alice -> Proxy 1      ACK sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf2      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=ffe254      Call-ID: 12345600@atlanta.example.com      Proxy-Authorization: Digest username="alice",       realm="example.com", nonce="ae9137be1c87d175c2dd63302a0d6e0a",       opaque="", uri="sips:bob@biloxi.example.com",       response="bbaec39f943bdcb3620d90afc548a45c"      CSeq: 3 ACK      Content-Length: 0      /* To hear the recording, Alice connects to the Error-Info URI. */      F10 INVITE Alice -> Proxy 1      INVITE sips:screen-fail-term-ann@ms.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfj      Max-Forwards: 70Johnston, et al.         Best Current Practice                [Page 129]

RFC 5359                  SIP Service Examples              October 2008      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 4 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000   F11 200 OK Announcement Server -> Proxy 1      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bfj       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=234934      Call-ID: 12345600@atlanta.example.com      CSeq: 4 INVITE      Contact: <sips:ms.biloxi.example.com>       ;automaton;+sip.rendering="no"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=annc 2890844543 2890844543 IN IP4 announce.biloxi.example.com      s=      c=IN IP4 announce.biloxi.example.com      t=0 0      m=audio 49174 RTP/AVP 0      a=rtpmap:0 PCMU/8000   F12 ACK Alice -> Announcement Server      ACK sips:ms.biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b32Johnston, et al.         Best Current Practice                [Page 130]

RFC 5359                  SIP Service Examples              October 2008      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=234934      Call-ID: 12345600@atlanta.example.com      CSeq: 4 ACK      Content-Length: 0      /* Announcement Server plays announcement then disconnects. */      F13 BYE Announcement Server -> Alice      BYE sips:alice@client.atlanta.example.com SIP/2.0      Via: SIP/2.0/TLS announcement.example.com:5061       ;branch=z9hG4bK74bKS      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=234934      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2334 BYE      Content-Length: 0      F14 200 OK Alice -> Announcement Server      SIP/2.0 200 OK      Via: SIP/2.0/TLS announcement.example.com:5061       ;branch=z9hG4bK74bKS       ;received=192.0.2.103      From: Bob <sips:bob@biloxi.example.com>;tag=234934      To: Alice <sips:alice@atlanta.example.com>;tag=1234567      Call-ID: 12345600@atlanta.example.com      CSeq: 2334 BYE      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 131]

RFC 5359                  SIP Service Examples              October 20082.14.  Call Management (Outgoing Call Screening)           Alice            Proxy           Bob             |                |              |             |    INVITE F1   |              |             |--------------->|              |             | 407 Proxy Authentication F2   |             |<---------------|              |             |     ACK F3     |              |             |--------------->|              |             |    INVITE F4   |              |             |--------------->|              |             | 403 Screening Failure (Originating) F5             |<---------------|              |             |     ACK F6     |              |             |--------------->|              |             |                |              |   Alice has an outgoing call screening list; Bob is included on the   list of addresses to which Alice will not be able to place a call.   Alice attempts to call Bob.   Alice could establish a session to listen to the announcement in the   Error-Info header field.   Message Details      F1 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0Johnston, et al.         Best Current Practice                [Page 132]

RFC 5359                  SIP Service Examples              October 2008      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      /* Proxy 1 challenges Alice for authentication. */      F2 407 Proxy Authentication Required Proxy 1 -> Alice      SIP/2.0 407 Proxy Authentication Required      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=90210      Call-ID: 12345600@atlanta.example.com      CSeq: 1 INVITE      Proxy-Authenticate: Digest realm="example.com",       nonce="ea9c8e88df84f1cec4341ae6cbe5a359",       qop="auth", nc=00000001, cnonce="0a4f113b",       opaque="", stale=FALSE, algorithm=MD5      Content-Length: 0      F3 ACK Alice -> Proxy 1      ACK sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74bf9      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=90210      Call-ID: 12345600@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* Alice responds be sending an INVITE with authentication         credentials in it. */      F4 INVITE Alice -> Proxy 1      INVITE sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b4      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>      Call-ID: 12345600@atlanta.example.comJohnston, et al.         Best Current Practice                [Page 133]

RFC 5359                  SIP Service Examples              October 2008      CSeq: 2 INVITE      Contact: <sips:alice@client.atlanta.example.com>      Proxy-Authorization: Digest username="alice", realm="example.com",       nonce="cb360afc54bbaec39f943bd820d9a45c", opaque="",       uri="sips:bob@biloxi.example.com",       response="b9d2e5bcdec9f69ab2a9b44f270285a6"      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Content-Type: application/sdp      Content-Length: ...      v=0      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com      s=      c=IN IP4 client.atlanta.example.com      t=0 0      m=audio 49170 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F5 403 Screening Failure (Originating) Proxy 1 -> Alice      SIP/2.0 403 Screening Failure (Originating)      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b4       ;received=192.0.2.103      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=18017      Call-ID: 12345600@atlanta.example.com      CSeq: 2 INVITE      Error-Info: <sips:screen-fail-orig-ann@announcement.example.com>      Content-Length: 0      F6 ACK Alice -> Proxy 1      ACK sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS client.atlanta.example.com:5061       ;branch=z9hG4bK74b4      Max-Forwards: 70      From: Alice <sips:alice@atlanta.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=18017      Call-ID: 12345600@atlanta.example.com      CSeq: 2 ACK      Proxy-Authorization: Digest username="alice", realm="example.com",       nonce="cb360afc54bbaec39f943bd820d9a45c", opaque="",       uri="sips:bob@biloxi.example.com",       response="b9d2e5bcdec9f69ab2a9b44f270285a6"      Content-Length: 0Johnston, et al.         Best Current Practice                [Page 134]

RFC 5359                  SIP Service Examples              October 20082.15.  Call Park           Alice           Bob        Park Server       Carol             |              |              |              |             |   INVITE F1  |              |              |             |------------->|              |              |             |180 Ringing F2|              |              |             |<-------------|              |              |             |  200 OK F3   |              |              |             |<-------------|              |              |             |    ACK F4    |              |              |             |------------->|              |              |             |  RTP Media   |              |              |             |<============>|              |              |             |      Bob Parks Call         |              |             |              |   REFER Refer-To: A F5      |             |              |------------->|              |             |              |    202 F6    |              |             |              |<-------------|              |             |              |   NOTIFY F7  |              |             |              |<-------------|              |             |              |    200 F8    |              |             |              |------------->|              |             |  INVITE F9 Replaces: B      |              |             |<----------------------------|              |             |          200 OK F10         |              |             |---------------------------->|              |             |           ACK F11           |              |             |<----------------------------|              |             |           RTP Music         |              |             |<===========================>|              |             |     BYE F12  |              |              |             |------------->|  NOTIFY F14  |              |             |  200 OK F13  |<-------------|              |             |<-------------|  200 OK F15  |              |             |              |------------->|              |             |              |   Carol picks up the call   |             |              |              |              |             |              |              | SUBSCRIBE F16|             |              |              |<-------------|             |              |              |  200 OK F17  |             |              |              |------------->|             |              |              |  NOTIFY F18  |             |              |              |------------->|             |              |              |  200 OK F19  |             |              |              |<-------------|             |           INVITE Replaces: Park Server F20 |             |<-------------------------------------------|Johnston, et al.         Best Current Practice                [Page 135]

RFC 5359                  SIP Service Examples              October 2008             |              |              |   200 F21    |             |------------------------------------------->|             |              |              |    ACK F22   |             |<-------------------------------------------|             |                  RTP Media                 |             |<==========================================>|             |           BYE F23           |              |             |---------------------------->|              |             |          200 OK F24         |              |             |<----------------------------|              |             |       No more RTP Music     |              |   In this example, Alice calls Bob.  Bob then parks the call at the   Park Server by sending a REFER to the Park Server.  The server sends   an INVITE to Alice, which replaces the session between Alice and Bob.   The Park Server utilizes the automaton, rendering, and byeless   feature tags in F9 to indicate its capabilities to Alice.  The call   is accepted by Alice and causes Alice to send a BYE to Bob.  Bob   receives notification of the successful park, and also receives the   dialog identifiers in the application/sip body of the NOTIFY   response.   Carol wishes to retrieve the call, so she sends an INVITE containing   the dialog identifiers to Alice, which replaces the session with the   Park Server.  Alice accepts the call and sends a BYE to the Park   Server.  Carol obtains the dialog identifiers from a NOTIFY from the   Park Server.   Note that this call flow is a special case of call transfer.   Note also that this flow could also be used for Music on Hold.   Message Details   F1 INVITE Alice -> Bob   INVITE sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.alice.example.com:5061    ;branch=z9hG4bKnashds7   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>   Call-ID: 12345601@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:a8342043f@atlanta.example.com;gr>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces, gruu   Content-Type: application/sdpJohnston, et al.         Best Current Practice                [Page 136]

RFC 5359                  SIP Service Examples              October 2008   Content-Length: ...   v=0   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com   s=   c=IN IP4 client.atlanta.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F2 180 Ringing Bob -> Alice   SIP/2.0 180 Ringing   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bKnashds7    ;received=192.0.2.105   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=314159   Call-ID: 12345601@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:bob@client.biloxi.example.com>   Content-Length: 0   F3 200 OK Bob -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bKnashds7    ;received=192.0.2.105   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=314159   Call-ID: 12345601@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:bob@client.biloxi.example.com>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...   v=0   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com   s=   c=IN IP4 client.biloxi.example.com   t=0 0   m=audio 3456 RTP/AVP 0   a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                [Page 137]

RFC 5359                  SIP Service Examples              October 2008   F4 ACK Alice -> Bob   ACK sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bKnashds7   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=314159   Call-ID: 12345601@atlanta.example.com   CSeq: 1 ACK   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Length: 0   /* Bob REFERs Park Server to establish session with Alice,      which replaces the established session between Alice and Bob.      Note that there is no session established between Bob      and the Park Server. */   F5 REFER Bob -> Park Server   REFER sips:park@server.example.com SIP/2.0   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bKnashds9   Max-Forwards: 70   From: Bob <sips:bob@biloxi.example.com>;tag=02134   To: Park Server <sips:park@server.example.com>   Call-ID: 4802029847@biloxi.example.com   CSeq: 1 REFER <allOneLine>   Refer-To: <sips:a8342043f@atlanta.example.com;gr?Replaces=   12345601%40atlanta.example.com%3Bfrom-tag%3D314159   %3Bto-tag%3D1234567&Require=replaces> </allOneLine>   Referred-By: <sips:bob@biloxi.example.com>   Contact: <sips:bob@client.biloxi.example.com>   Content-Length: 0   F6 202 Accepted Park Server -> Bob   SIP/2.0 202 Accepted   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bKnashds9    ;received=192.0.2.105   From: Bob <sips:bob@biloxi.example.com>;tag=02134   To: Park Server <sips:park@server.example.com>;tag=56323Johnston, et al.         Best Current Practice                [Page 138]

RFC 5359                  SIP Service Examples              October 2008   Call-ID: 4802029847@biloxi.example.com   Contact: <sips:park@server.example.com>   CSeq: 1 REFER   Content-Length: 0   F7 NOTIFY Park Server -> Bob   NOTIFY sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74bT6   To: Bob <sips:bob@biloxi.example.com>;tag=02134   Max-Forwards: 70   From: Park Server <sips:park@server.example.com>;tag=56323   Call-ID: 4802029847@biloxi.example.com   CSeq: 1 NOTIFY   Event: refer   Contact: <sips:park@server.example.com>   Subscription-State: active;expires=60   Content-Type: message/sipfrag   Content-Length: ...   SIP/2.0 100 Trying   F8 200 OK Bob -> Park Server   SIP/2.0 200 OK   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74bT6    ;received=192.0.2.103   To: Bob <sips:bob@biloxi.example.com>;tag=02134   From: Park Server <sips:park@server.example.com>;tag=56323   Call-ID: 4802029847@biloxi.example.com   CSeq: 1 NOTIFY   Content-Length: 0   /* Park Server places call to Alice to replace session      between Alice and Bob. */   F9 INVITE Park Server -> Alice   INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74rf   Max-Forwards: 70   From: <sips:park@server.example.com>;tag=0111Johnston, et al.         Best Current Practice                [Page 139]

RFC 5359                  SIP Service Examples              October 2008   To: <sips:a8342043f@atlanta.example.com;gr>   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 INVITE   Referred-By: <sips:bob@biloxi.example.com>   Contact: <sips:park@server.example.com>;automaton       ;+sip.byeless;+sip.rendering="no"   Require: replaces   Replaces: 12345601@atlanta.example.com    ;from-tag=314159;to-tag=1234567   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...   v=0   o=ParkServer 2890844576 2890844576 IN IP4 Park.server.example.com   s=   c=IN IP4 server.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F10 200 OK Alice -> Park Server   SIP/2.0 200 OK   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74rf    ;received=192.0.2.103   From: <sips:park@server.example.com>;tag=0111   To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 INVITE   Contact: <sips:a8342043f@atlanta.example.com;gr>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces, gruu   Content-Type: application/sdp   Content-Length: ...   v=0   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com   s=   c=IN IP4 client.atlanta.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   a=recvonlyJohnston, et al.         Best Current Practice                [Page 140]

RFC 5359                  SIP Service Examples              October 2008   F11 ACK Park Server -> Alice   ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK7rfF   Max-Forwards: 70   From: <sips:park@server.example.com>;tag=0111   To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 ACK   Content-Length: 0   F12 BYE Alice -> Bob   BYE sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bKnashds7   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=314159   Call-ID: 12345601@atlanta.example.com   CSeq: 2 BYE   Content-Length: 0   F13 200 OK Bob -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bKnashds7    ;received=192.0.2.105   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=314159   Call-ID: 12345601@atlanta.example.com   CSeq: 2 BYE   Content-Length: 0   /* Park Server reports success back to Bob by returning      a 200 OK response.  Bob obtains the dialog identifiers      from the headers included in the response. */   F14 NOTIFY Park Server -> Bob   NOTIFY sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74bf9Johnston, et al.         Best Current Practice                [Page 141]

RFC 5359                  SIP Service Examples              October 2008   To: Bob <sips:bob@biloxi.example.com>;tag=02134   Max-Forwards: 70   From: Park Server <sips:park@server.example.com>;tag=56323   Call-ID: 4802029847@biloxi.example.com   CSeq: 2 NOTIFY   Event: refer   Subscription-State: terminated;reason=noresource   Contact: <sips:park@server.example.com>;automaton       ;+sip.byeless;+sip.rendering="no"   Content-Type: message/sipfrag   Content-Length: ...   SIP/2.0 200 OK   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74rf    ;received=192.0.2.103   From: <sips:park@server.example.com>;tag=0111   To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 INVITE   Contact: <sips:a8342043f@atlanta.example.com;gr>   F15 200 OK Bob -> Park Server   SIP/2.0 200 OK   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74bf9    ;received=192.0.2.103   To: Bob <sips:bob@biloxi.example.com>;tag=02134   From: Park Server <sips:park@server.example.com>;tag=56323   Call-ID: 4802029847@biloxi.example.com   CSeq: 2 NOTIFY   Content-Length: 0   /* Alice is now parked at the Park Server. */   /* Carol picks up the call by sending an INVITE to A, which      replaces the existing session with the Park Server.      Carol needs to know the dialog information to construct      the Replaces header. */   F16 SUBSCRIBE  Carol -> Park Server   SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.chicago.example.com:5061    ;branch=z9hG4bK74b232Johnston, et al.         Best Current Practice                [Page 142]

RFC 5359                  SIP Service Examples              October 2008   Max-Forwards: 70   From: Carol <sips:carol@chicago.example.com>;tag=158x93461   To: <sips:park@server.example.com>   Call-ID: 2d6485356dfaj34dsf   CSeq: 1 SUBSCRIBE   Contact: <sips:carol@client.chicago.example.com>   Event: dialog   Expires: 0   Accept: application/dialog-info+xml   Content-Length: 0   F17 200 OK Park Server -> Carol   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.chicago.example.com:5061    ;branch=z9hG4bK74b232    ;received=192.0.2.105   From: Carol <sips:carol@chicago.example.com>;tag=158x93461   To: <sips:park@server.example.com>;tag=3213j   Call-ID: 2d6485356dfaj34dsf   CSeq: 1 SUBSCRIBE   Contact: <sips:park@server.example.com>;automaton       ;+sip.byeless;+sip.rendering="no"   Content-Length: 0   F18 NOTIFY  Park Server -> Carol   NOTIFY sips:carol@client.example.com SIP/2.0   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74b8skd   Max-Forwards: 70   To: Carol <sips:carol@chicago.example.com>;tag=158x93461   From: <sips:park@server.example.com>;tag=3213j   Call-ID: 2d6485356dfaj34dsf   CSeq: 1 NOTIFY   Contact: <sips:park@server.example.com>;automaton       ;+sip.byeless;+sip.rendering="no"   Event: dialog   Subscription-State: terminated;reason=timeout   Content-Type: application/dialog-info+xml   Content-Length: ...   <?xml version="1.0"?>   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"         version="0" state="full" entity="sips:park@server.example.com">      <dialog         call-id="a5-75-34-12-76@server.example.com"Johnston, et al.         Best Current Practice                [Page 143]

RFC 5359                  SIP Service Examples              October 2008         local-tag="0111" remote-tag="098594" direction="initiator">        <duration>1</duration>        <local>           <target>sips:park@server.example.com</target>        </local>        <remote>          <target>sips:a8342043f@atlanta.example.com;gr</target>        </remote>        <state>confirmed</state>      </dialog>    </dialog-info>   F19 200 OK Carol -> Park Server   SIP/2.0 200 OK   Via: SIP/2.0/TLS server.example.com:5061    ;branch=z9hG4bK74b8skd    ;received=192.0.2.103   To: Carol <sips:carol@chicago.example.com>;tag=158x93461   From: <sips:park@server.example.com>;tag=3213j   Call-ID: 2d6485356dfaj34dsf   CSeq: 1 NOTIFY   Contact: <sips:carol@client.chicago.example.com>   Content-Length: 0   F20 INVITE Carol -> Alice   INVITE sips:alice@atlanta.example.com SIP/2.0   Via: SIP/2.0/TLS client.chicago.example.com:5061    ;branch=z9hG4bK74bQ2   Max-Forwards: 70   From: Carol <sips:carol@chicago.example.com>;tag=5893461   To: Alice <sips:alice@atlanta.example.com>   Call-ID: 6485356@chicago.example.com   CSeq: 1 INVITE   Contact: <sips:carol@client.chicago.example.com>   Require: replaces   Replaces: a5-75-34-12-76@server.example.com    ;to-tag=098594;from-tag=0111   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,    SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...   v=0Johnston, et al.         Best Current Practice                [Page 144]

RFC 5359                  SIP Service Examples              October 2008   o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com   s=   c=IN IP4 client.chicago.example.com   t=0 0   m=audio 3456 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F21 200 OK Alice -> Carol   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.chicago.example.com:5061    ;branch=z9hG4bK74bQ2    ;received=192.0.2.105   From: Carol <sips:carol@chicago.example.com>;tag=5893461   To: Alice <sips:alice@atlanta.example.com>;tag=222   Call-ID: 6485356@chicago.example.com   CSeq: 1 INVITE   Contact: <sips:a8342043f@atlanta.example.com;gr>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces, gruu   Content-Type: application/sdp   Content-Length: ...   v=0   o=alice 2890844527 2890844527 IN IP4 client.atlanta.example.com   s=   c=IN IP4 client.atlanta.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F22 ACK Carol -> Alice   ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0   Via: SIP/2.0/TLS client.chicago.example.com:5061    ;branch=z9hG4bK74bJ0   Max-Forwards: 70   From: Carol <sips:carol@chicago.example.com>;tag=5893461   To: Alice <sips:alice@atlanta.example.com>;tag=222   Call-ID: 6485356@chicago.example.com   CSeq: 1 ACK   Content-Length: 0   /* A replaces the session to the Park Server with the new      session with C and generates a BYE to disconnect the      Park Server. */Johnston, et al.         Best Current Practice                [Page 145]

RFC 5359                  SIP Service Examples              October 2008   F23 BYE Alice -> Park Server   BYE sips:park@server.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74b4N   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=098594   To: <sips:park@server.example.com>;tag=0111   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 BYE   Content-Length: 0   F24 200 OK Park Server -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74b4N    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=098594   To: <sips:park@server.example.com>;tag=0111   Call-ID: a5-75-34-12-76@server.example.com   CSeq: 1 BYE   Content-Length: 0Johnston, et al.         Best Current Practice                [Page 146]

RFC 5359                  SIP Service Examples              October 20082.16.  Call Pickup            Alice          Bob                Bill             |              |                   |             |   INVITE F1  |                   |             |------------->|                   |             |180 Ringing F2|                   |             |<-------------|                   |             |              |   SUBSCRIBE F3    |             |              |<------------------|             |              |     200 OK F4     |             |              |------------------>|             |              |     NOTIFY F5     |             |              |------------------>|             |              |     200 OK F6     |             |              |<------------------|             |          INVITE Replaces:Bob  F7 |             |<---------------------------------|             |              |     200 OK F8     |             |--------------------------------->|             |   CANCEL F9  |                   |             |------------->|                   |             |  200 OK F10  |                   |             |<-------------|                   |             |    487 F11   |                   |             |<-------------|                   |             |    ACK F12   |                   |             |------------->|                   |             |                    ACK F13       |             |<---------------------------------|             |                                  |             |    Two-Way RTP Established       |             |<================================>|             |                     BYE F14      |             |--------------------------------->|             |                   200 OK F15     |             |<---------------------------------|             |                                  |   Bob and Bill are part of a work group at example.com that can pick up   each other's calls.  Alice calls Bob, who does not answer.  Bill   wishes to pick up the call and sends a SUBSCRIBE to Bob to retrieve   the dialog information.  Bill then generates an INVITE with a   Replaces to Alice.  Alice answers the INVITE and sends a CANCEL to   stop Bob's phone ringing.  Note that the relative order of the   487/ACK sequence (F11/F12) and the 200 OK to the CANCEL (F10) is not   deterministic.Johnston, et al.         Best Current Practice                [Page 147]

RFC 5359                  SIP Service Examples              October 2008   This call flow shows the use of the "early-only" parameter [RFC3891]   in the Replaces header field of F7.  This parameter prevents Alice   from accepting the INVITE if Bob has already accepted the INVITE.  If   Bill had wished to "take" the call from Bob regardless of whether he   had answered, the parameter would not have been present in F7.   Also note that the subscription between Bob and Carol could have been   established prior to Alice's call.   Message Details  F1 INVITE Alice -> Bob  INVITE sips:bob@biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf9  Max-Forwards: 70  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>  Call-ID: 12345600@atlanta.example.com  CSeq: 1 INVITE  Contact: <sips:a8342043f@atlanta.example.com;gr>  Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY  Supported: replaces, gruu  Content-Type: application/sdp  Content-Length: ...  v=0  o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com  s=  c=IN IP4 client.atlanta.example.com  t=0 0  m=audio 49170 RTP/AVP 0  a=rtpmap:0 PCMU/8000  F2 180 Ringing Bob -> Alice  SIP/2.0 180 Ringing  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf9   ;received=192.0.2.103  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>;tag=3145678  Call-ID: 12345600@atlanta.example.comJohnston, et al.         Best Current Practice                [Page 148]

RFC 5359                  SIP Service Examples              October 2008  CSeq: 1 INVITE  Contact: <sips:bob@client.biloxi.example.com>  Content-Length: 0  /* Bill decides to pick up the call. */  F3 SUBSCRIBE  Bill -> Bob  SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS pc.biloxi.example.com:5061   ;branch=z9hG4bK74bf  Max-Forwards: 70  From: Bill <sips:bill@biloxi.example.com>;tag=8675309  To: Bob <sips:bob@biloxi.example.com>  Call-ID: rt4353gs2egg@pc.biloxi.example.com  CSeq: 1 SUBSCRIBE  Contact: <sips:bill@pc.biloxi.example.com>  Event: dialog  Expires: 0  Accept: application/dialog-info+xml  Content-Length: 0  F4 200 OK Bob -> Bill  SIP/2.0 200 OK  Via: SIP/2.0/TLS pc.biloxi.example.com:5061   ;branch=z9hG4bK74bf   ;received=192.0.2.114  Max-Forwards: 70  From: Bill <sips:bill@biloxi.example.com>;tag=8675309  To: Bob <sips:bob@biloxi.example.com>;tag=31451098  Call-ID: rt4353gs2egg@pc.biloxi.example.com  CSeq: 1 SUBSCRIBE  Content-Length: 0  F5 NOTIFY  Bob -> Bill  NOTIFY sips:bill@pc.biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS client.biloxi.example.com:5061   ;branch=z9hG4bK74br  Max-Forwards: 70  From: Bob <sips:bob@biloxi.example.com>;tag=31451098  To: Bill <sips:bill@biloxi.example.com>;tag=8675309  Call-ID: rt4353gs2egg@pc.biloxi.example.com  CSeq: 1 NOTIFYJohnston, et al.         Best Current Practice                [Page 149]

RFC 5359                  SIP Service Examples              October 2008  Contact: <sips:bob@client.biloxi.example.com>  Event: dialog  Subscription-State: terminated;reason=timeout  Content-Type: application/dialog-info+xml  Content-Length: ...  <?xml version="1.0"?>  <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"         version="0" state="full" entity="sips:bob@biloxi.example.com">     <dialog call-id="12345600@atlanta.example.com"         local-tag="3145678" remote-tag="1234567" direction="recipient">       <duration>1</duration>       <local>         <identity display="Bob">sips:bob@biloxi.example.com</identity>         <target>sips:bob@client.biloxi.example.com</target>       </local>       <remote>         <identity display="Alice">sips:alice@atlanta.example.com                                                         </identity>         <target>sips:a8342043@atlanta.example.com;gr</target>       </remote>       <state>early</state>     </dialog>   </dialog-info>  F6 200 OK  Bill -> Bob  SIP/2.0 200 OK  Via: SIP/2.0/TLS client.biloxi.example.com:5061   ;branch=z9hG4bK74br   ;received=192.0.2.105  From: Bob <sips:bob@biloxi.example.com>;tag=31451098  To: Bill <sips:bill@biloxi.example.com>;tag=8675309  Call-ID: rt4353gs2egg@pc.biloxi.example.com  CSeq: 1 NOTIFY  Contact: <sips:bill@pc.biloxi.example.com>  Content-Length: 0  F7 INVITE  Bill -> Alice  INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0  Via: SIP/2.0/TLS pc.biloxi.example.com:5061   ;branch=z9hG4bK74HH  Max-Forwards: 70  From: Bill <sips:bill@biloxi.example.com>;tag=8675310  To: Alice <sips:alice@atlanta.example.com>Johnston, et al.         Best Current Practice                [Page 150]

RFC 5359                  SIP Service Examples              October 2008  Call-ID: 563456212@b2.biloxi.example.com  CSeq: 1 INVITE  Require: replaces  Replaces: 12345600@atlanta.example.com   ;from-tag=314578;to-tag=1234567;early-only  Contact: <sips:bill@pc.biloxi.example.com>  Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY  Supported: replaces  Content-Type: application/sdp  Content-Length: ...  v=0  o=bill 2890843122 2890843122 IN IP4 pc.biloxi.example.com  s=  c=IN IP4 pc.biloxi.example.com  t=0 0  m=audio 5342 RTP/AVP 0  a=rtpmap:0 PCMU/8000  /* Alice matches the dialog information in the Replaces header     and accepts the INVITE. */  F8 200 OK  Alice -> Bill  SIP/2.0 200 OK  Via: SIP/2.0/TLS pc.biloxi.example.com:5061   ;branch=z9hG4bK74HH   ;received=192.0.2.114  From: Bill <sips:bill@biloxi.example.com>;tag=8675310  To: Alice <sips:alice@atlanta.example.com>;tag=131256  Call-ID: 563456212@b2.biloxi.example.com  CSeq: 1 INVITE  Contact: <sips:a8342043f@atlanta.example.com;gr>  Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY  Supported: replaces, gruu  Content-Type: application/sdp  Content-Length: ...  v=0  o=alice 289084543 289084543 IN IP4 client.atlanta.example.com  s=  c=IN IP4 client.atlanta.example.com  t=0 0  m=audio 49172 RTP/AVP 0  a=rtpmap:0 PCMU/8000  /* Alice stops Bob's phone from ringing by sending a CANCEL. */Johnston, et al.         Best Current Practice                [Page 151]

RFC 5359                  SIP Service Examples              October 2008  F9 CANCEL Alice -> Bob  CANCEL sips:bob@biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf9  Max-Forwards: 70  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>  Call-ID: 12345600@atlanta.example.com  CSeq: 1 CANCEL  Content-Length: 0  F10 200 OK Bob -> Alice  SIP/2.0 200 OK  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf9   ;received=192.0.2.103  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>;tag=3145678  Call-ID: 12345600@atlanta.example.com  CSeq: 1 CANCEL  Content-Length: 0  F11 487 Request Terminated Bob -> Alice  SIP/2.0 487 Request Terminated  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf9   ;received=192.0.2.103  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>;tag=3145678  Call-ID: 12345600@atlanta.example.com  CSeq: 1 INVITE  Content-Length: 0  F12 ACK Alice -> Bob  ACK sips:bob@client.biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK83749.1  Max-Forwards: 70  From: Alice <sips:alice@atlanta.example.com>;tag=1234567  To: Bob <sips:bob@biloxi.example.com>;tag=3145678Johnston, et al.         Best Current Practice                [Page 152]

RFC 5359                  SIP Service Examples              October 2008  Call-ID: 12345600@atlanta.example.com  CSeq: 1 ACK  Content-Length: 0  F13 ACK  Bill -> Alice  ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0  Via: SIP/2.0/TLS pc.biloxi.example.com:5061   ;branch=z9hG4bK7435  Max-Forwards: 70  From: Bill <sips:bill@biloxi.example.com>;tag=8675310  To: Alice <sips:alice@atlanta.example.com>;tag=131256  Call-ID: 563456212@b2.biloxi.example.com  CSeq: 1 ACK  Content-Length: 0  /* RTP streams are established between Alice and Bill.     Later, Alice hangs up with Bill. */  F14 BYE Alice -> Bill  BYE sips:bill@pc.biloxi.example.com SIP/2.0  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf2  Max-Forwards: 70  To: Bill <sips:bill@biloxi.example.com>;tag=8675310  From: Alice <sips:alice@atlanta.example.com>;tag=131256  Call-ID: 563456212@b2.biloxi.example.com  CSeq: 1 BYE  Content-Length: 0  F15 200 OK Bill -> Alice  SIP/2.0 200 OK  Via: SIP/2.0/TLS client.atlanta.example.com:5061   ;branch=z9hG4bK74bf2   ;received=192.0.2.105  To: Bill <sips:bill@biloxi.example.com>;tag=8675310  From: Alice <sips:alice@atlanta.example.com>;tag=131256  Call-ID: 563456212@b2.biloxi.example.com  CSeq:  1 BYE  Content-Length: 0Johnston, et al.         Best Current Practice                [Page 153]

RFC 5359                  SIP Service Examples              October 20082.17.  Automatic Redial           Alice             Bob             |                |             |    INVITE F1   |             |--------------->|             |486 Busy Here F2|             |<---------------|    Bob is busy             |     ACK F3     |             |--------------->|             |  SUBSCRIBE F4  |             |--------------->|             |   200 OK F5    |             |<---------------|             |    NOTIFY F6   |             |<---------------|             |   200 OK F7    |             |--------------->|             |                |             |    NOTIFY F8   |    Bob is now available             |<---------------|             |   200 OK F9    |             |--------------->|             |                |             |   INVITE F10   |             |--------------->|    Session setup successful             | 180 Ringing F11|             |<---------------|             |   200 OK F12   |             |<---------------|             |     ACK F13    |             |--------------->|             |  Media Session |             |<==============>|             |                |             |   NOTIFY F14   |             |<---------------|             |   200 OK F15   |             |--------------->|             |                |             |  SUBSCRIBE F16 | Alice terminates subscription             |--------------->|             |   200 OK F17   |             |<---------------|             |   NOTIFY F18   |             |<---------------|             |   200 OK F19   |             |--------------->|             |                |Johnston, et al.         Best Current Practice                [Page 154]

RFC 5359                  SIP Service Examples              October 2008   Bob is initially busy when Alice calls.  Alice subscribes to Bob's   call state using a SUBSCRIBE F4.  Bob sends a NOTIFY F8 when Bob is   available.  Alice is alerted, then Alice sends an INVITE to Bob to   establish the session.  The subscription is terminated using   SUBSCRIBE F16.   Message Details   F1 INVITE Alice -> Bob   INVITE sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bf9   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>   Call-ID: 12345600@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:alice@client.atlanta.example.com>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...   v=0   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com   s=   c=IN IP4 client.atlanta.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F2 486 Busy Here   SIP/2.0 486 Busy Here   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bf9    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=982039i4   Call-ID: 12345600@atlanta.example.com   CSeq: 1 INVITE   Content-Length: 0Johnston, et al.         Best Current Practice                [Page 155]

RFC 5359                  SIP Service Examples              October 2008   F3 ACK Alice -> Bob   ACK sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bf9   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=1234567   To: Bob <sips:bob@biloxi.example.com>;tag=982039i4   Call-ID: 12345600@atlanta.example.com   CSeq: 1 ACK   Content-Length: 0   F4 SUBSCRIBE Alice -> Bob   SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74b8G   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=837348234   To: Bob <sips:bob@biloxi.example.com>   Call-ID: 4524526232@atlanta.example.com   CSeq: 1 SUBSCRIBE   Contact: sips:alice@client.atlanta.example.com   Event: dialog   Accept: application/dialog-info+xml   Content-Length: 0   F5 200 OK Bob -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74b8G    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=837348234   To: Bob <sips:bob@biloxi.example.com>;tag=341123   Call-ID: 4524526232@atlanta.example.com   Expires: 60   CSeq: 1 SUBSCRIBE   Contact: sips:bob@client.biloxi.example.com   Content-Length: 0Johnston, et al.         Best Current Practice                [Page 156]

RFC 5359                  SIP Service Examples              October 2008   F6 NOTIFY Bob -> Alice   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK74bn2   Max-Forwards: 70   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 1 NOTIFY   Contact: <sips:bob@client.biloxi.example.com>   Event: dialog   Subscription-State: active;expires=59   Content-Type: application/dialog-info+xml   Content-Length: ...   <?xml version="1.0"?>   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"          version="0" state="full" entity="sips:bob@biloxi.example.com">      <dialog>         <duration>1</duration>        <state>confirmed</state>      </dialog>    </dialog-info>   F7 200 OK Alice -> Bob   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK74bn2    ;received=192.0.2.105   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 1 NOTIFY   Content-Length: 0   /* Bob is now available. */   F8 NOTIFY Bob -> Alice   NOTIFY sips:alice@atlanta.example.com SIP/2.0   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK74bVi   Max-Forwards: 70   From: Bob <sips:bob@biloxi.example.com>;tag=341123Johnston, et al.         Best Current Practice                [Page 157]

RFC 5359                  SIP Service Examples              October 2008   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 2 NOTIFY   Event: dialog   Subscription-State: active;expires=27   Contact: <sips:bob@client.biloxi.example.com>   Content-Type: application/dialog-info+xml   Content-Length: ...   <?xml version="1.0"?>   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"          version="0" state="full" entity="sips:bob@biloxi.example.com">      <dialog>        <state>terminated</state>      </dialog>   </dialog-info>   F9 200 OK Alice -> Bob   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK74bVi    ;received=192.0.2.105   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 2 NOTIFY   Content-Length: 0   F10 INVITE Alice -> Bob   INVITE sips:bob@biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bfq   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k   To: Bob <sips:bob@biloxi.example.com>   Call-ID: aoij4i9okitr@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:alice@client.atlanta.example.com>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...Johnston, et al.         Best Current Practice                [Page 158]

RFC 5359                  SIP Service Examples              October 2008   v=0   o=alice 2890844826 2890844826 IN IP4 client.atlanta.example.com   s=   c=IN IP4 client.atlanta.example.com   t=0 0   m=audio 49170 RTP/AVP 0   a=rtpmap:0 PCMU/8000   F11 180 Ringing Bob -> Alice   SIP/2.0 180 Ringing   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bfq    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k   To: Bob <sips:bob@biloxi.example.com>;tag=23431   Call-ID: aoij4i9okitr@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:bob@client.biloxi.example.com>   Content-Length: 0   F12 200 OK Bob -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bfq    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k   To: Bob <sips:bob@biloxi.example.com>;tag=23431   Call-ID: aoij4i9okitr@atlanta.example.com   CSeq: 1 INVITE   Contact: <sips:bob@client.biloxi.example.com>   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY   Supported: replaces   Content-Type: application/sdp   Content-Length: ...   v=0   o=bob 2890854527 2890854527 IN IP4 client.biloxi.example.com   s=   c=IN IP4 client.biloxi.example.com   t=0 0   m=audio 3456 RTP/AVP 0   a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                [Page 159]

RFC 5359                  SIP Service Examples              October 2008   F13 ACK Alice -> Bob   ACK sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK74bLBJ   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k   To: Bob <sips:bob@biloxi.example.com>;tag=23431   Call-ID: aoij4i9okitr@atlanta.example.com   CSeq: 1 ACK   Content-Length: 0   F14 NOTIFY Bob -> Alice   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK4bnd2   Max-Forwards: 70   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 3 NOTIFY   Contact: <sips:bob@client.biloxi.example.com>   Event: dialog   Subscription-State: active;expires=15   Content-Type: application/dialog-info+xml   Content-Length: ...   <?xml version="1.0"?>   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"          version="0" state="full" entity="sips:bob@biloxi.example.com">      <dialog>         <duration>1</duration>        <state>confirmed</state>      </dialog>    </dialog-info>   F15 200 OK Alice -> Bob   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bK4bnd2    ;received=192.0.2.105   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234Johnston, et al.         Best Current Practice                [Page 160]

RFC 5359                  SIP Service Examples              October 2008   Call-ID: 4524526232@atlanta.example.com   CSeq: 3 NOTIFY   Content-Length: 0   /* Alice terminates the subscription. */   F16 SUBSCRIBE Alice -> Bob   SUBSCRIBE sips:bob@client.biloxi.example.com SIP/2.0   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK474b8   Max-Forwards: 70   From: Alice <sips:alice@atlanta.example.com>;tag=837348234   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 2 SUBSCRIBE   Contact: sips:alice@client.atlanta.example.com   Event: dialog   Expires: 0   Accept: application/dialog-info+xml   Content-Length: 0   F17 200 OK Bob -> Alice   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.atlanta.example.com:5061    ;branch=z9hG4bK474b8    ;received=192.0.2.103   From: Alice <sips:alice@atlanta.example.com>;tag=837348234   To: Bob <sips:bob@biloxi.example.com>;tag=341123   Call-ID: 4524526232@atlanta.example.com   Expires: 0   CSeq: 2 SUBSCRIBE   Contact: sips:bob@client.biloxi.example.com   Content-Length: 0   F18 NOTIFY Bob -> Alice   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bKb5n2j   Max-Forwards: 70   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.comJohnston, et al.         Best Current Practice                [Page 161]

RFC 5359                  SIP Service Examples              October 2008   CSeq: 4 NOTIFY   Contact: <sips:bob@client.biloxi.example.com>   Event: dialog   Subscription-State: terminated;reason=noresource   Content-Type: application/dialog-info+xml   Content-Length: ...   <?xml version="1.0"?>   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"          version="0" state="full" entity="sips:bob@biloxi.example.com">      <dialog>         <duration>3</duration>        <state>confirmed</state>      </dialog>    </dialog-info>   F19 200 OK Alice -> Bob   SIP/2.0 200 OK   Via: SIP/2.0/TLS client.biloxi.example.com:5061    ;branch=z9hG4bKb5n2j    ;received=192.0.2.105   From: Bob <sips:bob@biloxi.example.com>;tag=341123   To: Alice <sips:alice@atlanta.example.com>;tag=837348234   Call-ID: 4524526232@atlanta.example.com   CSeq: 4 NOTIFY   Content-Length: 0Johnston, et al.         Best Current Practice                [Page 162]

RFC 5359                  SIP Service Examples              October 20082.18.  Click to Dial        Bob's PC                Bob                Carol            | REFER Refer-To:Carol F1                 |            |------------------->|                    |            |  202 Accepted F2   |                    |            |<-------------------|                    |            |                    |     INVITE F3      |            |                    |------------------->|            |                    |   180 Ringing F4   |            |                    |<-------------------|            |                    |     200 OK F5      |            |                    |<-------------------|            |                    |       ACK F6       |            |                    |------------------->|            |                    |         RTP        |            |                    |<==================>|            |                    |                    |   In this example, while browsing the web on his PC, Bob clicks on   Carol's SIP URI, intending to establish a session with Carol.  Bob's   web browser passes the SIP URI to the SIP client on Bob's PC.  The PC   client is configured with the URI of Bob's SIP phone.  A REFER is   sent to the SIP phone, which results in the establishment of the   session between Bob and Carol.   Note that Bob's PC requests that no REFER dialog be established by   the use of the Refer-Sub: false header field [RFC4488].   This flow is preferable to the 3pcc flow because the end-to-end SIP   signaling is not interrupted by the 3pcc controller, and because   Bob's experience of the call will not be marred by the lack of   ringback tone or possible clipping.  Suitable authorization of the   REFER and explicit authorization of the triggered INVITE by Bob are   necessary.   Message Details   /* Bob's PC SIP client sends a REFER to Bob's SIP phone. */      F1 REFER PC -> Bob      REFER sips:bob@biloxi.example.com SIP/2.0      Via: SIP/2.0/TLS pc.biloxi.example.com:5061       ;branch=z9hG4bKnashds7      Max-Forwards: 70      From: <sips:pc.biloxi.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>Johnston, et al.         Best Current Practice                [Page 163]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 1234560183434      CSeq: 1 REFER      Refer-To: <sips:carol@chicago.example.com>      Refer-Sub: false      Contact: <sips:pc.biloxi.example.com>      Content-Length: 0      F2 202 Accepted Bob -> PC      SIP/2.0 202 Accepted      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashds7       ;received=192.0.2.103      From: <sips:pc.biloxi.example.com>;tag=1234567      To: Bob <sips:bob@biloxi.example.com>;tag=314159      Call-ID: 1234560183434      Contact: <sips:bob@client.biloxi.example.com>      CSeq: 1 REFER      Refer-Sub: false      Content-Length: 0      F3 INVITE Bob -> Carol      INVITE sips:carol@chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdK9      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:bob@client.biloxi.example.com>      Referred-By: <sips:pc.biloxi.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=bob 2890844539 2890844539 IN IP4 client.biloxi.example.com      s=      c=IN IP4 client.biloxi.example.com      t=0 0      m=audio 3458 RTP/AVP 0      a=rtpmap:0 PCMU/8000Johnston, et al.         Best Current Practice                [Page 164]

RFC 5359                  SIP Service Examples              October 2008      F4 180 Ringing Carol -> Bob      SIP/2.0 180 Ringing      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdK9       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Content-Length: 0      F5 200 OK Carol -> Bob      SIP/2.0 200 OK      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashdK9       ;received=192.0.2.113      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287      Call-ID: 7436222@atlanta.example.com      CSeq: 1 INVITE      Contact: <sips:carol@client.chicago.example.com>      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY      Supported: replaces      Content-Type: application/sdp      Content-Length: ...      v=0      o=carol 2890844527 2890844527 IN IP4 client.chicago.example.com      s=      c=IN IP4 client.chicago.example.com      t=0 0      m=audio 3456 RTP/AVP 0      a=rtpmap:0 PCMU/8000      F6 ACK Bob -> Carol      ACK sips:carol@client.chicago.example.com SIP/2.0      Via: SIP/2.0/TLS client.biloxi.example.com:5061       ;branch=z9hG4bKnashd43      Max-Forwards: 70      From: Bob <sips:bob@biloxi.example.com>;tag=8675309      To: Carol <sips:carol@chicago.example.com>;tag=928287Johnston, et al.         Best Current Practice                [Page 165]

RFC 5359                  SIP Service Examples              October 2008      Call-ID: 7436222@atlanta.example.com      CSeq: 1 ACK      Content-Length: 0      /* Bob and Carol now have established a session. */3.  Security Considerations   Since many of the examples in this document involve SIP call control,   either peer-to-peer or 3pcc, the security considerations in the   Multiparty Framework document [FRAMEWORK] apply.   Many of the services shown in this document rely on a particular user   agent being part of a group.  Members of a group could be, for   example, employees within a particular department, a set of home   phone extensions, members of a call center, etc.  As such, user   agents that are part of the group permit other group members special   privileges and features.  For example, while a user agent may not in   general allow another user agent to learn detailed dialog   information, this information might be shared with another group   member in order to facilitate a service such as call pickup.  Group   members must be authenticated using normal SIP means such as   certificates or shared secrets.   The service examples in this document make extensive use of the SIP   call control primitives REFER, Replaces, Join, and the dialog   package.  The security considerations associated with each of these   extensions [RFC3515], [RFC3891], [RFC3911], [RFC4235] apply to the   scenarios in this document.4.  Acknowledgements   The authors would like to thank the following reviewers of the   document for their detailed comments and corrections: Vijay Gurbani,   John Elwell, Joel Repiquet, Nagesh Kumar, Chandra Ravipati, Eric   Burger, Jeroen Bemmel, Miguel Garcia, and Dale Worley.   The Transfer - Instant Messaging call flow is based on the "IM-a-   call" call flow by Jonathan Rosenberg and Henning Schulzrinne.  The   Automatic Redial call flow is based on a call flow by Adam Roach.   The authors wish to thank the following individuals for their   assistance and review of this call flows document: Joel Repiquet, Aki   Neimi, Rohan Mahy, Jonathan Rosenberg, Hemant Agrawal, Henry   Sinnreich, Dean Willis, David Devanatham, Joe Pizzimenti, Matt   Cannon, John Hearty, the whole MCI WorldCom IPOP Design team, ScottJohnston, et al.         Best Current Practice                [Page 166]

RFC 5359                  SIP Service Examples              October 2008   Orton, Greg Osterhout, Pat Sollee, Doug Weisenberg, Danny Mistry,   Steve McKinnon, and Denise Ingram, Denise Caballero, Tom Redman, Ilya   Slain, Pat Sollee, John Truetken, and others from MCI WorldCom, 3Com,   Cisco, Lucent, and Nortel.5.  References5.1.  Normative References   [RFC3261]    Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,                A., Peterson, J., Sparks, R., Handley, M., and E.                Schooler, "SIP: Session Initiation Protocol",RFC 3261,                June 2002.   [RFC3264]    Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model                with Session Description Protocol (SDP)",RFC 3264,                June 2002.   [RFC3265]    Roach, A., "Session Initiation Protocol (SIP)-Specific                Event Notification",RFC 3265, June 2002.   [RFC3428]    Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema,                C., and D. Gurle, "Session Initiation Protocol (SIP)                Extension for Instant Messaging",RFC 3428,                December 2002.   [RFC3515]    Sparks, R., "The Session Initiation Protocol (SIP) Refer                Method",RFC 3515, April 2003.   [RFC3840]    Rosenberg, J., Schulzrinne, H., and P. Kyzivat,                "Indicating User Agent Capabilities in the Session                Initiation Protocol (SIP)",RFC 3840, August 2004.   [RFC3891]    Mahy, R., Biggs, B., and R. Dean, "The Session                Initiation Protocol (SIP) "Replaces" Header",RFC 3891,                September 2004.   [RFC3911]    Mahy, R. and D. Petrie, "The Session Initiation Protocol                (SIP) "Join" Header",RFC 3911, October 2004.   [RFC4235]    Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE-                Initiated Dialog Event Package for the Session                Initiation Protocol (SIP)",RFC 4235, November 2005.   [RFC4488]    Levin, O., "Suppression of Session Initiation Protocol                (SIP) REFER Method Implicit Subscription",RFC 4488,                May 2006.Johnston, et al.         Best Current Practice                [Page 167]

RFC 5359                  SIP Service Examples              October 2008   [RFC4579]    Johnston, A. and O. Levin, "Session Initiation Protocol                (SIP) Call Control - Conferencing for User Agents",BCP 119,RFC 4579, August 2006.5.2.  Informative References   [FRAMEWORK]  Mahy, R., Sparks, R., Rosenberg, J., Petrie, D., and A.                Johnston, "A Call Control and Multi-party usage                framework for the Session Initiation Protocol (SIP)",                Work in Progress, April 2008.   [GRUU]       Rosenberg, J., "Obtaining and Using Globally Routable                User Agent (UA) URIs (GRUU) in the Session Initiation                Protocol (SIP)", Work in Progress, October 2007.   [RFC3665]    Johnston, A., Donovan, S., Sparks, R., Cunningham, C.,                and K. Summers, "Session Initiation Protocol (SIP) Basic                Call Flow Examples",BCP 75,RFC 3665, December 2003.   [RFC3725]    Rosenberg, J., Peterson, J., Schulzrinne, H., and G.                Camarillo, "Best Current Practices for Third Party Call                Control (3pcc) in the Session Initiation Protocol                (SIP)",BCP 85,RFC 3725, April 2004.   [RFC4317]    Johnston, A. and R. Sparks, "Session Description                Protocol (SDP) Offer/Answer Examples",RFC 4317,                December 2005.   [RFC4475]    Sparks, R., Hawrylyshen, A., Johnston, A., Rosenberg,                J., and H. Schulzrinne, "Session Initiation Protocol                (SIP) Torture Test Messages",RFC 4475, May 2006.   [TRANSFER]   Sparks, R. and A. Johnston, "Session Initiation Protocol                Call Control - Transfer", Work in Progress,                September 2008.Johnston, et al.         Best Current Practice                [Page 168]

RFC 5359                  SIP Service Examples              October 2008Authors' Addresses   Alan Johnston (editor)   Avaya   St. Louis, MO  63124   EMail: alan@sipstation.com   Robert J. Sparks   Tekelec   EMail: RjS@nostrum.com   Chris Cunningham   Cisco Systems   EMail: chrcunni@cisco.com   Steve Donovan   Cisco Systems   EMail: srd@cisco.com   Kevin Summers   Sonus   Plano, TX  75093   EMail: ksummers@sonusnet.comJohnston, et al.         Best Current Practice                [Page 169]

RFC 5359                  SIP Service Examples              October 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Johnston, et al.         Best Current Practice                [Page 170]

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