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Network Working Group                                        M. LonnforsRequest for Comments: 5263                              J. Costa-RequenaCategory: Standards Track                                    E. Leppanen                                                                   Nokia                                                            H. Khartabil                                                                Ericsson                                                          September 2008Session Initiation Protocol (SIP) Extension forPartial Notification of Presence InformationStatus 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   By default, presence delivered using the presence event package for   the Session Initiation Protocol (SIP) is represented in the Presence   Information Data Format (PIDF).  A PIDF document contains a set of   elements, each representing a different aspect of the presence being   reported.  When any subset of the elements change, even just a single   element, a new document containing the full set of elements is   delivered.  This memo defines an extension allowing delivery of only   the presence data that has actually changed.Lonnfors, et al.            Standards Track                     [Page 1]

RFC 5263                  Partial Notification            September 2008Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .33.  Introduction to the Partial Notification Mechanism . . . . . .33.1.  Basic Presence Agent Operation . . . . . . . . . . . . . .33.2.  Operation with Partial Notification  . . . . . . . . . . .34.  Client and Server Operations . . . . . . . . . . . . . . . . .44.1.  Content-Type for Partial Notifications . . . . . . . . . .44.2.  Watcher Generation of SUBSCRIBE Requests . . . . . . . . .44.3.  Presence Agent Processing of SUBSCRIBE Requests  . . . . .44.4.  Presence Agent Generation of Partial Notifications . . . .54.5.  Watcher Processing of NOTIFY Requests  . . . . . . . . . .65.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .76.  Security Considerations  . . . . . . . . . . . . . . . . . . .137.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .138.  References . . . . . . . . . . . . . . . . . . . . . . . . . .148.1.  Normative References . . . . . . . . . . . . . . . . . . .148.2.  Informative References . . . . . . . . . . . . . . . . . .141.  Introduction   A presence event package for Session Initiation Protocol (SIP) [3]   allows users ('watchers') to subscribe to other users'   ('presentities') presence information.  The presence information is   composed of multiple pieces of data that are delivered to the   watcher.  The size of the presence information document can be large   (i.e., the presence document can contain an arbitrary number of   elements called presence tuples that convey data).  As specified inRFC 2778 [9] and the presence event package for SIP [3], a Presence   Agent (PA) always delivers in presence notifications all the presence   data that has been authorized for a certain watcher.  This is done   regardless of what presence data has changed compared to last   notification.  It may not be reasonable to send the complete presence   information over low bandwidth and high latency links when only part   of the presence information has actually changed.  This may end up   degrading the presence service and causing bad perception at the   watcher side.   This document defines a partial notification approach where the   presence server delivers to the watchers only those parts of the   presence information that have changed compared to the presence   information sent in the previous notifications.  This reduces the   amount of data that is transported over the network.   This mechanism utilizes the presence event package for SIP [3] and a   new MIME type for carrying partial Presence Information Data Format   documents [2].Lonnfors, et al.            Standards Track                     [Page 2]

RFC 5263                  Partial Notification            September 20082.  Conventions   In this document, the key words "MUST", "MUST NOT", "REQUIRED",   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",   and "OPTIONAL" are to be interpreted as described inRFC 2119 [1] and   indicate requirement levels for compliant implementations.   This document makes use of the vocabulary defined inRFC 2778 [9],RFC 3265 [6], the presence event package for SIP [3], and the PIDF   extension for Partial Presence [2].3.  Introduction to the Partial Notification Mechanism   This chapter briefly introduces the regular functionality of the   presence service, and gives an overview of the partial notification   solution.  This section is informational in nature.  It does not   contain any normative statements.3.1.  Basic Presence Agent Operation   The presence service normally operates so that a watcher sends a SIP   SUBSCRIBE request targeted to the presentity.  The request is routed   to the presence agent where the presentity's presence information is   stored.  The SUBSCRIBE request can include an Accept header field   that indicates the supported content types.   The presence agent receives the SUBSCRIBE request and if there is no   Accept header indicating the supported content types or the Accept   header contains the default PIDF content type, the PA will generate   presence notifications using the default PIDF format [5].  The PIDF   document can contain one or multiple XML elements.  The PIDF document   includes a set of elements defined inRFC 2778 [9], and its   extensions for representing the presence information.  This PIDF   document will be carried in the body of a NOTIFY request constructed   as perRFC 3265 [6].  During basic operation, the presence document   always contains the full state corresponding to the presence status   of the presentity, as determined by the PA local policy and   authorization rules.3.2.  Operation with Partial Notification   The partial notification mechanism allows a watcher to request that,   whenever possible, notifications contain only presence information   that has actually changed.  A watcher that wants to receive partial   notifications according to this document, creates a SIP SUBSCRIBE   request similar to that of a regular presence subscription.  However,   the SIP SUBSCRIBE request contains an Accept header field whose valueLonnfors, et al.            Standards Track                     [Page 3]

RFC 5263                  Partial Notification            September 2008   contains the "application/pidf-diff+xml" tag as well as the   "application/pidf+xml" tag.   When the presence agent receives the subscription, it examines the   Accept header field value and if the "application/pidf-diff+xml"   value is present, it can decide to use the partial notifications   mechanism specified in this memo.  The presence agent builds NOTIFY   requests that contain the Content-Type header field set to   "application/pidf-diff+xml".  The first NOTIFY request that contains   presence information will contain a full presence document.   Subsequent NOTIFY requests can contain partial presence documents.   This behavior is described in detail inSection 4.4.  Client and Server Operations   Unless otherwise specified in this document, the regular watcher and   presence agent behavior is applied as defined in the SIP presence   event package [3].4.1.  Content-Type for Partial Notifications   Entities supporting the partial notification extension described in   this document MUST support the 'application/pidf-diff+xml' content   type specified in the PIDF extension for partial presence [2].4.2.  Watcher Generation of SUBSCRIBE Requests   A SUBSCRIBE request can be used to negotiate the preferred content   type to be used in the notifications.  The Accept header field is   used for this purpose as specified inRFC 3261 [4].  When a watcher   wants to allow the presence agent to send partial notifications the   watcher MUST include an Accept header field in its SUBSCRIBE request.   The value of the Accept header field MUST contain 'application/   pidf-diff+xml' (in addition to 'application/pidf+xml' required by the   SIP presence event package [3]).  The watcher MAY include a "q"   parameter with each Accept value to indicate the relative preference   of that value.4.3.  Presence Agent Processing of SUBSCRIBE Requests   The presence agent receives subscriptions from watchers and generates   notifications according to the SIP presence event package [3].  If   the watcher has indicated the supported content types in the Accept   header field of the SUBSCRIBE request, the presence agent compares   the values included in the Accept header field with the supported   ones, and decides which one to use.  If the watcher has indicated   preferred accept values by means of "q" parameters, the presenceLonnfors, et al.            Standards Track                     [Page 4]

RFC 5263                  Partial Notification            September 2008   agent SHOULD base the decision on those preferences, unless otherwise   indicated by the presence agent local policy.4.4.  Presence Agent Generation of Partial Notifications   Once a subscription is accepted and installed, the PA MUST deliver   the full state of the presence information in the first partial   notification that contains a presence document having <pidf-full>   root element.  If the presence agent decides to send notifications   that include a presence document according to this specification, the   presence agent MUST build a presence document according to the PIDF   extension for Partial Presence [2] and MUST set the Content-Type   header field to the value 'application/pidf-diff+xml'.   When using the 'application/pidf-diff+xml' MIME type, the PA MUST   include a "version" attribute; for the first partial notification   (within a given subscription), the PA MUST initialize version to   value one (1).  This version counter is scoped to the subscription,   and is incremented by one within each partial notification.  The   version value is only reset when the given subscription is   terminated.  It is not reset when the subscription is refreshed.   When the PA generates a partial presence document, the PA SHOULD   include only that presence information that has changed compared to   the previous notifications.  It is up to the PA's local policy to   determine what is considered as a change to the previous state.   The PA MUST construct the partial presence document according to the   following logic:   o  The PA MUST construct the presence information according to the      PIDF extension for Partial Presence [2].  All the information that      has been added to the presence document is listed inside <add>      elements.  All information that has been removed from the presence      document is listed inside <remove> elements, and all information      that has been changed is listed under <replace> elements.   o  The PA MUST include a "version" attribute in the presence      document.  The PA MUST increment the version number by one      compared to the earlier successfully sent presence document in the      PIDF extension for Partial Presence [2] format to the watcher      associated with a certain subscription.   The PA MUST NOT send a new NOTIFY request that contains a partial   notification for the same Request-URI until it has received a final   response from the watcher for the previous one or the previous NOTIFY   request has timed out.Lonnfors, et al.            Standards Track                     [Page 5]

RFC 5263                  Partial Notification            September 2008   When the PA receives a SUBSCRIBE request (refresh or termination)   within the associated subscription, it SHOULD send a NOTIFY request   containing the full presence document.   If the PA has used other than the 'application/pidf-diff+xml' content   type in notifications within the existing subscription, and changes   to deliver partial notifications, the PA MUST deliver the full state   of the presence information containing a presence document having   <pidf-full> root element as the first partial notification.4.5.  Watcher Processing of NOTIFY Requests   Watcher processes all NOTIFY requests that contain 'application/   pidf+xml' content type as specified inRFC 3856 [3].   When the watcher receives the first notification containing the   'application/pidf-diff+xml' MIME body the watcher MUST initialize an   internal version counter, related to this subscription, to the value   of the "version" included in the presence document.  This version   counter is scoped to the subscription.  The watcher MUST also store   the received full presence document as its local copy.   When the watcher receives a subsequent 'application/pidf-diff+xml'   encoded presence document the watcher MUST compare the received   "version" attribute with the local version counter.  If the watcher   receives a presence document with the "version" attribute value equal   or lower than the locally stored version number, it is considered a   PA failure, and the watcher SHOULD discard the document without   further processing.  Otherwise, the watcher MUST modify its locally   stored information according to the following logic:   o  If the root element of the presence document is <pidf-full>, the      watcher must replace its local copy of the presence document with      the presence document received in the 'application/pidf-diff+xml'      body and set the internal version value to the value of the      "version" attribute included in the presence document.   o  If the root element of the presence document is <pidf-diff> and      the received version number is incremented by one compared with      the local version counter, the watcher MUST apply the changes to      its local copy of the full presence document indicated in the      received 'application/pidf-diff+xml' document as specified in PIDF      extension for Partial Presence [2].  The watcher MUST increment      the local version counter by one.Lonnfors, et al.            Standards Track                     [Page 6]

RFC 5263                  Partial Notification            September 2008   o  If the root element of the presence document is <pidf-diff> and      the received "version" value is higher by more than one compared      with the locally stored value, the watcher assumes that one or      more NOTIFYs were lost.  The watcher SHOULD either refresh the      subscription in order to receive a full presence document or      terminate the subscription.   If the watcher encounters a processing error while processing the   received 'application/pidf-diff+xml' encoded presence document, look   at Section 5.1 of [8].  In this case, the watcher SHOULD renew the   subscription.  The watcher MAY also fall back to normal presence   operations by not inserting 'application/pidf-diff+xml' in a new   SUBSCRIBE request.  It is hardly reasonable to signal this error to   the notifier even if the error exists in the notifier process.   If the PA changes the content type used in notifications within the   existing subscription, the watcher MUST discard all the previously   received presence information (except local version counter) from   that particular presentity and process the new content as specified   for that content type.  The local version counter MUST NOT be   discarded because if the PA changes back to 'application/   pidf-diff+xml', the MIME type version counter will continue to   increase from the last version value.5.  Examples   The following message flow shows an example applying the partial   notifications mechanism.   A watcher sends a SUBSCRIBE request declaring support for the default   presence format ('application/pidf+xml) and for the partial   notification format ('application/pidf-diff+xml') in the Accept   header field value.  The watcher uses the "q" parameter to set the   preference for receiving partial notifications.  The PA accepts the   subscription and, based on the "q" parameter value, selects to send   partial notifications in NOTIFY requests.  The first NOTIFY request   includes the full state of presence information.  The following   notifications only include information about delta of the presence   information from the previous NOTIFY requests.Lonnfors, et al.            Standards Track                     [Page 7]

RFC 5263                  Partial Notification            September 2008       Watcher                   Presence Agent                  PUA            | F1 SUBSCRIBE              |                         |            |-------------------------->|                         |            | F2 200 OK                 |                         |            |<--------------------------|                         |            | F3 NOTIFY                 |                         |            |<--------------------------|                         |            | F4 200 OK                 |                         |            |-------------------------->|                         |            |                           |                         |            |                           |   Update presence       |            |                           |<----------------------- |            |                           |                         |            | F5 NOTIFY                 |                         |            |<--------------------------|                         |            | F6 200 OK                 |                         |            |-------------------------->|                         |         Message Details      F1 SUBSCRIBE   watcher->example.com server            SUBSCRIBE sip:resource@example.com SIP/2.0            Via: SIP/2.0/TCP watcherhost.example.com;              branch=z9hG4bKnashds7            To: <sip:resource@example.com>            From: <sip:watcher@example.com> ;tag=xfg9            Call-ID: 2010@watcherhost.example.com            CSeq: 17766 SUBSCRIBE            Max-Forwards: 70            Event: presence            Accept: application/pidf+xml;q=0.3,              application/pidf-diff+xml;q=1            Contact: <sip:user@watcherhost.example.com>            Expires: 3600            Content-Length: 0Lonnfors, et al.            Standards Track                     [Page 8]

RFC 5263                  Partial Notification            September 2008      The PA accepts the subscription and generates a 200 OK response      to the SUBSCRIBE request         F2 200 OK   example.com server ->watcher            SIP/2.0 200 OK            Via: SIP/2.0/TCP watcherhost.example.com;              branch=z9hG4bKnashds7              ;received=192.0.2.1            To: <sip:resource@example.com>;tag=ffd2            From: <sip:watcher@example.com>;tag=xfg9            Call-ID: 2010@watcherhost.example.com            CSeq: 17766 SUBSCRIBE            Event: presence            Expires: 3600            Contact: <sip:server.example.com>            Content-Length: 0      The PA, based on the "q" parameter value in the Accept header      of the SUBSCRIBE request (F1), decides to use partial      notifications.  The PA creates the first NOTIFY request that      includes the full presence document.         F3 NOTIFY  example.com server -> watcher            NOTIFY sip:user@watcherhost.example.com SIP/2.0            Via: SIP/2.0/TCP server.example.com;              branch=z9hG4bKna998sk            To: <sip:watcher@example.com>;tag=xfg9            From: <sip:resource@example.com>;tag=ffd2            Call-ID: 2010@watcherhost.example.com            Event: presence            Subscription-State: active;expires=3599            Max-Forwards: 70            CSeq: 8775 NOTIFY            Contact: <sip:server.example.com>            Content-Type: application/pidf-diff+xml            Content-Length: ...   <?xml version="1.0" encoding="UTF-8"?>      <p:pidf-full xmlns="urn:ietf:params:xml:ns:pidf"             xmlns:p="urn:ietf:params:xml:ns:pidf-diff"             xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"             xmlns:c="urn:ietf:params:xml:ns:pidf:caps"             xmlns:cp="urn:ietf:params:xml:ns:pidf:cipid"             xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"             entity="sip:resource@example.com"             version="1">Lonnfors, et al.            Standards Track                     [Page 9]

RFC 5263                  Partial Notification            September 2008       <tuple>        <status>         <basic>open</basic>        </status>        <c:servcaps>         <c:audio>true</c:audio>         <c:video>false</c:video>         <c:message>true</c:message>        </c:servcaps>         <r:relationship><r:assistant/></r:relationship>        <contact priority="0.8">tel:09012345678</contact>       </tuple>       <tuple>        <status>         <basic>open</basic>        </status>        <contact priority="1.0">im:res@example.com</contact>       </tuple>       <tuple>        <status>         <basic>closed</basic>        </status>        <cp:homepage>http://example.com/~res/</cp:homepage>        <cp:icon>http://example.com/~res/icon.gif</cp:icon>        <cp:card>http://example.com/~res/card.vcd</cp:card>        <contact priority="0.9">sip:resource@example.com</contact>       </tuple>       <note xml:lang="en">Full state presence document</note>       <dm:person>         <r:activities>          <r:on-the-phone/>          <r:busy/>         </r:activities>       </dm:person>Lonnfors, et al.            Standards Track                    [Page 10]

RFC 5263                  Partial Notification            September 2008       <dm:device>         <c:devcaps>          <c:mobility>           <c:supported>            <c:mobile/>           </c:supported>          </c:mobility>         </c:devcaps>         <dm:deviceID>mac:xxx</dm:deviceID>       </dm:device>      </p:pidf-full>         F4 200 OK watcher -> example.com server            SIP/2.0 200 OK            Via: SIP/2.0/TCP server.example.com;              branch=z9hG4bKna998sk              ;received=192.0.2.2            To: <sip:watcher@example.com>;tag=xfg9            From: <sip:resource@example.com>;tag=ffd2            Call-ID: 2010@watcherhost.example.com            CSeq: 8775 NOTIFY            Content-Length: 0            At a later time, the presentity's presence information            changes.  The PA generates a NOTIFY request            that includes information about the changes.      F5 NOTIFY example.com server -> watcher            NOTIFY sip:user@watcherhost.example.com SIP/2.0            Via: SIP/2.0/TCP server.example.com;              branch=z9hG4bKna998sl            To: <sip:watcher@example.com>;tag=xfg9            From: <sip:resource@example.com>;tag=ffd2            Call-ID: 2010@watcherhost.example.com            CSeq: 8776 NOTIFY            Event: presence            Subscription-State: active;expires=3543            Max-Forwards: 70            Contact: <sip:server.example.com>            Content-Type: application/pidf-diff+xml            Content-Length: ...Lonnfors, et al.            Standards Track                    [Page 11]

RFC 5263                  Partial Notification            September 2008      <?xml version="1.0" encoding="UTF-8"?>      <p:pidf-diff xmlns="urn:ietf:params:xml:ns:pidf"                   xmlns:p="urn:ietf:params:xml:ns:pidf-diff"                   xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"                   xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"                entity="sip:resource@example.com"                version="2">       <p:add sel="presence/note" pos="before"><tuple>        <status>         <basic>open</basic>        </status>        <contact priority="0.4">mailto:res@example.com</contact>        <note xml:lang="en">This is a new tuple inserted              between the last tuple and note element</note>       </tuple>       </p:add>       <p:replace sel="*/tuple[@id='r1230d']/status/basic/text()"        >open</p:replace>       <p:remove sel="*/dm:person/r:activities/r:busy"/>       <p:replace sel="*/tuple[@id='cg231jcr']/contact/@priority"        >0.7</p:replace>      </p:pidf-diff>      F6 200 OK watcher-> example.com server            SIP/2.0 200 OK            Via: SIP/2.0/TCP server.example.com;              branch=z9hG4bKna998sl             ;received=192.0.2.2            To: <sip:watcher@example.com>;tag=xfg9            From: <sip:resource@example.com>;tag=ffd2            Call-ID: 2010@watcherhost.example.com            CSeq: 8776 NOTIFY            Content-Length: 0Lonnfors, et al.            Standards Track                    [Page 12]

RFC 5263                  Partial Notification            September 20086.  Security Considerations   This specification relies on the presence event package for SIP [3].   Partial notifications can reveal information about what has changed   compared to the previous notification.  This can make it easier for   an eavesdropper to know what kind of changes are happening in the   presentity's presence information.  However, the same information can   be found if the presence event package is used with baseline PIDF   [5].   A third party can inject a NOTIFY request with partial state that   will cause the watcher to think it has missed a partial notification   and to request a new full presence document.  This is no worse than   what we have without this extension since a party that could perform   such action could also send a NOTIFY with Subscription-State:   terminated and achieve the same effect without knowing about the   extension.  Partial Notification does not make the situation any   worse, and the protection mechanisms from the existing system apply   to preventing this attack against the partial notification mechanism.   Presence-related security considerations are extensively discussed in   the presence event package for SIP [3] and all those identified   security considerations apply to this document as well.  Issues   described in the presence event package for SIP [3], including   confidentiality, message integrity and authenticity, outbound   authentication, replay prevention, Denial-of-Service (DoS) attacks   against thirst parties and DoS attacks against servers all apply here   without any change.   It is RECOMMENDED that TLS [7] be used between elements to provide   hop-by-hop confidentially protection.  Furthermore, S/MIME MAY be   used for integrity and authenticity of SUBSCRIBE and NOTIFY requests.   This is described inSection 23 of RFC 3261.7.  Acknowledgments   The authors would like to thank Jari Urpalainen, Jyrki Aarnos,   Jonathan Rosenberg, Dean Willis, Kriztian Kiss, Juha Kalliokulju,   Miguel Garcia, Anders Kristensen, Yannis Pavlidis, Ben Cambell,   Robert Sparks, and Tim Moran for their valuable comments.Lonnfors, et al.            Standards Track                    [Page 13]

RFC 5263                  Partial Notification            September 20088.  References8.1.  Normative References   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.   [2]  Lonnfors, M., Khartabil, H., Leppanen, E., and J. Urpalainen,        "Presence Information Data Format (PIDF) Extension for Partial        Presence",RFC 5262, August 008.   [3]  Rosenberg, J., "A Presence Event Package for the Session        Initiation Protocol (SIP)",RFC 3856, August 2004.   [4]  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.   [5]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and        J. Peterson, "Presence Information Data Format (PIDF)",RFC 3863, August 2004.   [6]  Roach, A., "SIP-Specific Event Notification",RFC 3265,        June 2002.   [7]  Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1",RFC 4346, April 2006.   [8]  Urpalainen, J., "An Extensible Markup Language (XML) Patch        Operations Framework Utilizing XML Path Language (XPath)        Selectors",RFC 5261, September 2008.8.2.  Informative References   [9]  Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence and        Instant Messaging",RFC 2778, February 2000.Lonnfors, et al.            Standards Track                    [Page 14]

RFC 5263                  Partial Notification            September 2008Authors' Addresses   Mikko Lonnfors   Nokia   P.O. Box 321   Helsinki   Finland   Phone: +358 71 8008000   EMail: mikko.lonnfors@nokia.com   Jose Costa-Requena   Nokia   P.O. Box 321   Helsinki   Finland   Phone: +358 71 8008000   EMail: jose.costa-requena@nokia.com   Eva Leppanen   Nokia   Lempaala   Finland   EMail: eva.leppanen@saunalahti.fi   Hisham Khartabil   Ericsson   Melbourne   Australia   Phone: +61 416 108 890   EMail: hisham.khartabil@gmail.comLonnfors, et al.            Standards Track                    [Page 15]

RFC 5263                  Partial Notification            September 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.Lonnfors, et al.            Standards Track                    [Page 16]