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Network Working Group                                       G. CamarilloRequest for Comments: 5366                                      EricssonCategory: Standards Track                                    A. Johnston                                                                   Avaya                                                            October 2008Conference Establishment Using Request-Contained Listsin the Session Initiation Protocol (SIP)Status of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   This document describes how to create a conference using SIP URI-list   services.  In particular, it describes a mechanism that allows a User   Agent Client to provide a conference server with the initial list of   participants using an INVITE-contained URI list.Table of Contents1. Introduction ....................................................22. Terminology .....................................................23. User Agent Client Procedures ....................................23.1. Response Handling ..........................................23.2. Re-INVITE Request Generation ...............................34. URI-List Document Format ........................................35. Conference Server Procedures ....................................55.1. Re-INVITE Request Handling .................................66. Example .........................................................67. Security Considerations ........................................108. IANA Considerations ............................................109. Acknowledgments ................................................1110. References ....................................................1110.1. Normative References .....................................1110.2. Informative References ...................................12Camarillo & Johnston        Standards Track                     [Page 1]

RFC 5366                 INVITE-Contained Lists             October 20081.  IntroductionSection 5.4 of [RFC4579] describes how to create a conference using   ad hoc SIP [RFC3261] methods.  The client sends an INVITE request to   a conference factory URI and receives the actual conference URI,   which contains the "isfocus" feature tag, in the Contact header field   of a response -- typically a 200 (OK) response.   Once the UAC (User Agent Client) obtains the conference URI, it can   add participants to the newly created conference in several ways,   which are described in [RFC4579].   Some environments have tough requirements regarding conference   establishment time.  They require the UAC to be able to request the   creation of an ad hoc conference and to provide the conference server   with the initial set of participants in a single operation.  This   document describes how to meet this requirement using the mechanism   to transport URI lists in SIP messages described in [RFC5363].2.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].3.  User Agent Client Procedures   A UAC that wants to include the set of initial participants in its   initial INVITE request to create an ad hoc conference adds a body   whose disposition type is 'recipient-list', as defined in [RFC5363],   with a URI list that contains the participants that the UAC wants the   conference server to invite.  Additionally, the UAC MUST include the   'recipient-list-invite' option-tag (which is registered with the IANA   inSection 8) in a Require header field.  The UAC sends this INVITE   request to the conference factory URI.   The INVITE transaction is also part of an offer/answer exchange that   will establish a session between the UAC and the conference server,   as specified in [RFC4579].  Therefore, the INVITE request may need to   carry a multipart body: a session description and a URI list.3.1.  Response Handling   The status code in the response to the INVITE request does not   provide any information about whether or not the conference server   was able to bring the users in the URI list into the conference.   That is, a 200 (OK) response means that the conference was created   successfully, that the UAC that generated the INVITE request is inCamarillo & Johnston        Standards Track                     [Page 2]

RFC 5366                 INVITE-Contained Lists             October 2008   the conference, and that the server understood the URI list.  If the   UAC wishes to obtain information about the status of other users in   the conference, it SHOULD use general conference mechanisms, such as   the conference package, which is defined in [RFC4575].3.2.  Re-INVITE Request Generation   The previous sections have specified how to include a URI list in an   initial INVITE request to a conference server.  Once the INVITE-   initiated dialog between the UAC and the conference server has been   established, the UAC can send subsequent INVITE requests (typically   referred to as re-INVITE requests) to the conference server to, for   example, modify the characteristics of the media exchanged with the   server.   At this point, there are no semantics associated with 'recipient-   list' bodies in re-INVITE requests (although future extensions may   define them).  Therefore, UACs SHOULD NOT include 'recipient-list'   bodies in re-INVITE requests sent to a conference server.      Note that a difference between an initial INVITE request and a      re-INVITE request is that while the initial INVITE request is sent      to the conference factory URI, the re-INVITE request is sent to      the URI provided by the server in a Contact header field when the      dialog was established.  Therefore, from the UAC's point of view,      the resource identified by the former URI supports 'recipient-      list' bodies, while the resource identified by the latter does not      support them.4.  URI-List Document Format   As described in [RFC5363], specifications of individual URI-list   services, like the conferencing service described here, need to   specify a default format for 'recipient-list' bodies used within the   particular service.   The default format for 'recipient-list' bodies for conferencing UAs   (User Agents) is the XML resource list format (which is specified in   [RFC4826]) extended with the "Extensible Markup Language (XML) Format   Extension for Representing Copy Control Attributes in Resource Lists"   [RFC5364].  Consequently, conferencing UACs generating 'recipient-   list' bodies MUST support both of these formats and MAY support other   formats.  Conferencing servers able to handle 'recipient-list' bodies   MUST support both of these formats and MAY support other formats.   As described in "Extensible Markup Language (XML) Format Extension   for Representing Copy Control Attributes in Resource Lists"   [RFC5364], each URI can be tagged with a 'copyControl' attribute setCamarillo & Johnston        Standards Track                     [Page 3]

RFC 5366                 INVITE-Contained Lists             October 2008   to either "to", "cc", or "bcc", indicating the role in which the   recipient will get the INVITE request.  Additionally, URIs can be   tagged with the 'anonymize' attribute to prevent the conference   server from disclosing the target URI in a URI list.   In addition, "Extensible Markup Language (XML) Format Extension for   Representing Copy Control Attributes in Resource Lists" [RFC5364]   defines a 'recipient-list-history' body that contains the list of   recipients.  The default format for 'recipient-list-history' bodies   for conferencing UAs is also the XML resource list document format   specified in [RFC4826] extended with "Extensible Markup Language   (XML) Format Extension for Representing Copy Control Attributes in   Resource Lists" [RFC5364].  Consequently, conferencing UACs able to   generate 'recipient-list-history' bodies MUST support these formats   and MAY support others.  Conferencing UAs able to understand   'recipient-list-history' MUST support these formats and MAY support   others.  Conferencing servers able to handle 'recipient-list-history'   bodies MUST support these formats and MAY support others.   Nevertheless, the XML resource list document specified in [RFC4826]   provides features, such as hierarchical lists and the ability to   include entries by reference relative to the XML Configuration Access   Protocol (XCAP) root URI, that are not needed by the conferencing   service defined in this document, which only needs to transfer a flat   list of URIs between a UA (User Agent) and the conference server.   Therefore, when using the default resource list document,   conferencing UAs SHOULD use flat lists (i.e., no hierarchical lists)   and SHOULD NOT use <entry-ref> elements.  A conference factory   application receiving a URI list with more information than what has   just been described MAY discard all the extra information.   Figure 1 shows an example of a flat list that follows the XML   resource list document (specified in [RFC4826]) extended with   "Extensible Markup Language (XML) Format Extension for Representing   Copy Control Attributes in Resource Lists" [RFC5364].   <?xml version="1.0" encoding="UTF-8"?>   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"             xmlns:cp="urn:ietf:params:xml:ns:copycontrol">     <list>       <entry uri="sip:bill@example.com" cp:copyControl="to"  />       <entry uri="sip:joe@example.org" cp:copyControl="cc" />       <entry uri="sip:ted@example.net" cp:copyControl="bcc" />     </list>   </resource-lists>                            Figure 1: URI listCamarillo & Johnston        Standards Track                     [Page 4]

RFC 5366                 INVITE-Contained Lists             October 20085.  Conference Server Procedures   Conference servers that are able to receive and process INVITE   requests with a 'recipient-list' body SHOULD include a 'recipient-   list-invite' option-tag in a Supported header field when responding   to OPTIONS requests.   On reception of an INVITE request containing a 'recipient-list' body   as described inSection 3, a conference server MUST follow the rules   described in [RFC4579] to create ad hoc conferences.  Once the ad hoc   conference is created, the conference server SHOULD attempt to add   the participants in the URI list to the conference as if their   addition had been requested using any of the methods described in   [RFC4579].   The INVITE transaction is also part of an offer/answer exchange that   will establish a session between the UAC and the conference server,   as specified in [RFC4579].  Therefore, the INVITE request may carry a   multipart body: a session description and a URI list.   Once the conference server has created the ad hoc conference and has   attempted to add the initial set of participants, the conference   server behaves as a regular conference server and MUST follow the   rules in [RFC4579].   The incoming INVITE request will contain a URI-list body or reference   (as specified in [RFC5363]) with the actual list of recipients.  If   this URI list includes resources tagged with the 'copyControl'   attribute set to a value of "to" or "cc", the conference server   SHOULD include a URI list in each of the outgoing INVITE requests.   This list SHOULD be formatted according to the XML format for   representing resource lists (specified in [RFC4826]) and the   copyControl extension specified in [RFC5364].   The URI-list service MUST follow the procedures specified in   [RFC5364] with respect to the handling of the 'anonymize', 'count',   and 'copyControl' attributes.   If the conference server includes a URI list in an outgoing INVITE   request, it MUST include a Content-Disposition header field (which is   specified in [RFC2183]) with the value set to 'recipient-list-   history' and a 'handling' parameter (as specified in [RFC3204]) set   to "optional".Camarillo & Johnston        Standards Track                     [Page 5]

RFC 5366                 INVITE-Contained Lists             October 20085.1.  Re-INVITE Request Handling   At this point, there are no semantics associated with 'recipient-   list' bodies in re-INVITE requests (although future extensions may   define them).  Therefore, a conference server receiving a re-INVITE   request with a 'recipient-list' body and, consequently, a   'recipient-list-invite' option-tag, following standard SIP   procedures, rejects it with a 420 (Bad Extension), which carries an   Unsupported header field listing the 'recipient-list-invite' option-   tag.      This is because the resource identified by the conference URI does      not actually support this extension.  On the other hand, the      resource identified by the conference factory URI does support      this extension and, consequently, would include the 'recipient-      list-invite' option-tag in, for example, responses to OPTIONS      requests.6.  Example   Figure 2 shows an example of operation.  A UAC sends an INVITE   request (F1) that contains an SDP body and a URI list to the   conference server.  The conference server answers with a 200 (OK)   response and generates an INVITE request to each of the UASs (User   Agent Servers) identified by the URIs included in the URI list.  The   conference server includes SDP and a manipulated URI list in each of   the outgoing INVITE requests.Camarillo & Johnston        Standards Track                     [Page 6]

RFC 5366                 INVITE-Contained Lists             October 2008   +--------+        +---------+      +--------+ +--------+ +--------+   |SIP UAC |        | confer. |      |SIP UAS | |SIP UAS | |SIP UAS |   |        |        | server  |      |   1    | |   2    | |   n    |   +--------+        +---------+      +--------+ +--------+ +--------+       |                  |               |          |          |       | F1 INVITE        |               |          |          |       | ---------------->|               |          |          |       | F2 200 OK        |               |          |          |       |<---------------- |  F3 INVITE    |          |          |       |                  | ------------->|          |          |       |                  |  F4 INVITE    |          |          |       |                  | ------------------------>|          |       |                  |  F5 INVITE    |          |          |       |                  | ----------------------------------->|       |                  |  F6 200 OK    |          |          |       |                  |<------------- |          |          |       |                  |  F7 200 OK    |          |          |       |                  |<------------------------ |          |       |                  |  F8 200 OK    |          |          |       |                  |<----------------------------------- |       |                  |               |          |          |       |                  |               |          |          |       |                  |               |          |          |                      Figure 2: Example of operation   Figure 3 shows an example of the INVITE request F1, which carries a   multipart/mixed body composed of two other bodies: an application/sdp   body that describes the session and an application/resource-lists+xml   body that contains the list of target URIs.   INVITE sip:conf-fact@example.com SIP/2.0   Via: SIP/2.0/TCP atlanta.example.com       ;branch=z9hG4bKhjhs8ass83   Max-Forwards: 70   To: "Conf Factory" <sip:conf-fact@example.com>   From: Alice <sip:alice@example.com>;tag=32331   Call-ID: d432fa84b4c76e66710   CSeq: 1 INVITE   Contact: <sip:alice@atlanta.example.com>   Allow: INVITE, ACK, CANCEL, BYE, REFER   Allow-Events: dialog   Accept: application/sdp, message/sipfrag   Require: recipient-list-invite   Content-Type: multipart/mixed;boundary="boundary1"   Content-Length: 690Camarillo & Johnston        Standards Track                     [Page 7]

RFC 5366                 INVITE-Contained Lists             October 2008   --boundary1   Content-Type: application/sdp   v=0   o=alice 2890844526 2890842807 IN IP4 atlanta.example.com   s=-   c=IN IP4 192.0.2.1   t=0 0   m=audio 20000 RTP/AVP 0   a=rtpmap:0 PCMU/8000   m=video 20002 RTP/AVP 31   a=rtpmap:31 H261/90000   --boundary1   Content-Type: application/resource-lists+xml   Content-Disposition: recipient-list   <?xml version="1.0" encoding="UTF-8"?>   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"             xmlns:cp="urn:ietf:params:xml:ns:copyControl">     <list>       <entry uri="sip:bill@example.com" cp:copyControl="to" />       <entry uri="sip:randy@example.net" cp:copyControl="to"                                          cp:anonymize="true"/>       <entry uri="sip:eddy@example.com" cp:copyControl="to"                                         cp:anonymize="true"/>       <entry uri="sip:joe@example.org" cp:copyControl="cc" />       <entry uri="sip:carol@example.net" cp:copyControl="cc"                                          cp:anonymize="true"/>       <entry uri="sip:ted@example.net" cp:copyControl="bcc" />       <entry uri="sip:andy@example.com" cp:copyControl="bcc" />     </list>   </resource-lists>   --boundary1--        Figure 3: INVITE request received at the conference server   The INVITE requests F3, F4, and F5 are similar in nature.  All those   INVITE requests contain a multipart/mixed body that is composed of   two other bodies: an application/sdp body describing the session and   an application/resource-lists+xml containing the list of recipients.   The application/resource-lists+xml bodies are not equal to the   application/resource-lists+xml included in the received INVITE   request F1, because the conference server has anonymized those URIs   tagged with the 'anonymize' attribute and has removed those URIs   tagged with a "bcc" 'copyControl' attribute.  Figure 4 shows an   example of the message F3.Camarillo & Johnston        Standards Track                     [Page 8]

RFC 5366                 INVITE-Contained Lists             October 2008   INVITE sip:bill@example.com SIP/2.0   Via: SIP/2.0/TCP conference.example.com       ;branch=z9hG4bKhjhs8as454   Max-Forwards: 70   To: <sip:bill@example.com>   From: Conference Server <sip:conf34@example.com>;tag=234332   Call-ID: 389sn189dasdf   CSeq: 1 INVITE   Contact: <sip:conf34@conference.example.com>;isfocus   Allow: INVITE, ACK, CANCEL, BYE, REFER   Allow-Events: dialog, conference   Accept: application/sdp, message/sipfrag   Content-Type: multipart/mixed;boundary="boundary1"   Content-Length: 690   --boundary1   Content-Type: application/sdp   v=0   o=conf 2890844343 2890844343 IN IP4 conference.example.com   s=-   c=IN IP4 192.0.2.5   t=0 0   m=audio 40000 RTP/AVP 0   a=rtpmap:0 PCMU/8000   m=video 40002 RTP/AVP 31   a=rtpmap:31 H261/90000   --boundary1   Content-Type: application/resource-lists+xml   Content-Disposition: recipient-list-history; handling=optional   <?xml version="1.0" encoding="UTF-8"?>   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"             xmlns:cp="urn:ietf:params:xml:ns:copycontrol">     <list>       <entry uri="sip:bill@example.com" cp:copyControl="to" />       <entry uri="sip:anonymous@anonymous.invalid" cp:copyControl="to"                                                    cp:count="2"/>       <entry uri="sip:joe@example.org" cp:copyControl="cc" />       <entry uri="sip:anonymous@anonymous.invalid" cp:copyControl="cc"                                                    cp:count="1"/>     </list>   </resource-lists>   --boundary1--          Figure 4: INVITE request sent by the conference serverCamarillo & Johnston        Standards Track                     [Page 9]

RFC 5366                 INVITE-Contained Lists             October 20087.  Security Considerations   This document discusses setup of SIP conferences using a request-   contained URI list.  Both conferencing and URI-list services have   specific security requirements, which are summarized here.   Conferences generally have authorization rules about who can or   cannot join a conference, what type of media can or cannot be used,   etc.  This information is used by the focus to admit or deny   participation in a conference.  It is RECOMMENDED that these types of   authorization rules be used to provide security for a SIP conference.   For this authorization information to be used, the focus needs to be   able to authenticate potential participants.  Normal SIP mechanisms,   including Digest authentication and certificates, can be used.  These   conference-specific security requirements are discussed further in   the requirements and framework documents -- [RFC4245] and [RFC4353].   For conference creation using a list, there are some additional   security considerations.  "Framework and Security Considerations for   Session Initiation Protocol (SIP) URI-List Services" [RFC5363]   discusses issues related to SIP URI-list services.  Given that a   conference server sending INVITE requests to a set of users acts as a   URI-list service, implementations of conference servers that handle   lists MUST follow the security-related rules in [RFC5363].  These   rules include opt-in lists and mandatory authentication and   authorization of clients.8.  IANA Considerations   This document defines the 'recipient-list-invite' SIP option-tag.  It   has been registered in the Option Tags subregistry under the SIP   parameter registry.  The following is the description used in the   registration:   +------------------------+------------------------------+-----------+   | Name                   | Description                  | Reference |   +------------------------+------------------------------+-----------+   | recipient-list-invite  | The body contains a list of  | [RFC5366] |   |                        | URIs that indicates the      |           |   |                        | recipients of the SIP INVITE |           |   |                        | request                      |           |   +------------------------+------------------------------+-----------+     Table 1: Registration of the 'recipient-list-invite' option-tag                                  in SIPCamarillo & Johnston        Standards Track                    [Page 10]

RFC 5366                 INVITE-Contained Lists             October 20089.  Acknowledgments   Cullen Jennings, Hisham Khartabil, Jonathan Rosenberg, and Keith   Drage provided useful comments on this document.  Miguel Garcia-   Martin assembled the dependencies to the 'copyControl' attribute   extension.10.  References10.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2183]  Troost, R., Dorner, S., and K. Moore, Ed., "Communicating              Presentation Information in Internet Messages: The              Content-Disposition Header Field",RFC 2183, August 1997.   [RFC3204]  Zimmerer, E., Peterson, J., Vemuri, A., Ong, L., Audet,              F., Watson, M., and M. Zonoun, "MIME media types for ISUP              and QSIG Objects",RFC 3204, December 2001.   [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.   [RFC4579]  Johnston, A. and O. Levin, "Session Initiation Protocol              (SIP) Call Control - Conferencing for User Agents",BCP119,RFC 4579, August 2006.   [RFC4826]  Rosenberg, J., "Extensible Markup Language (XML) Formats              for Representing Resource Lists",RFC 4826, May 2007.   [RFC5363]  Camarillo, G. and A.B. Roach, "Framework and Security              Considerations for Session Initiation Protocol (SIP) URI-              List Services",RFC 5363, October 2008.   [RFC5364]  Garcia-Martin, M. and G. Camarillo, "Extensible Markup              Language (XML) Format Extension for Representing Copy              Control Attributes in Resource Lists",RFC 5364, October              2008.Camarillo & Johnston        Standards Track                    [Page 11]

RFC 5366                 INVITE-Contained Lists             October 200810.2.  Informative References   [RFC4245]  Levin, O. and R. Even, "High-Level Requirements for              Tightly Coupled SIP Conferencing",RFC 4245, November              2005.   [RFC4353]  Rosenberg, J., "A Framework for Conferencing with the              Session Initiation Protocol (SIP)",RFC 4353, February              2006.   [RFC4575]  Rosenberg, J., Schulzrinne, H., and O. Levin, Ed., "A              Session Initiation Protocol (SIP) Event Package for              Conference State",RFC 4575, August 2006.Authors' Addresses   Gonzalo Camarillo   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   EMail: Gonzalo.Camarillo@ericsson.com   Alan Johnston   Avaya   St. Louis, MO  63124   USA   EMail: alan@sipstation.comCamarillo & Johnston        Standards Track                    [Page 12]

RFC 5366                 INVITE-Contained Lists             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.Camarillo & Johnston        Standards Track                    [Page 13]