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Versions: (draft-ietf-sipping-uri-list-subscribe) 00 01 02 RFC 5367

SIPPING Working Group                                       G. Camarillo
Internet-Draft                                                  Ericsson
Expires: March 21, 2007                                         A. Roach
                                                        Estacado Systems
                                                                O. Levin
                                                   Microsoft Corporation
                                                      September 17, 2006


    Subscriptions to Request-Contained Resource Lists in the Session
                       Initiation Protocol (SIP)
                draft-ietf-sip-uri-list-subscribe-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document specifies a way to create subscription to a list of
   resources in SIP.  This is achieved by including the list of
   resources in the body of a SUBSCRIBE.  Instead of having a subscriber
   send a SUBSCRIBE for each resource individually, the subscriber



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   defines the resource list, subscribes to it, and gets notifications
   about changes in the resources' state using a single SUBSCRIBE
   dialog.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Providing a Resource List Server with a URI-List . . . . . . .  3
   4.  URI-List Format  . . . . . . . . . . . . . . . . . . . . . . .  3
   5.  Resource List Server Behavior  . . . . . . . . . . . . . . . .  4
   6.  Subsequent SUBSCRIBEs  . . . . . . . . . . . . . . . . . . . .  4
   7.  Option-tag . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   8.  Providing a URI to Manipulate a Resource List  . . . . . . . .  5
   9.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   10. Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   12. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . .  7
   13. Normative References . . . . . . . . . . . . . . . . . . . . .  7
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9
   Intellectual Property and Copyright Statements . . . . . . . . . . 10





























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1.  Introduction

   RFC 4662 [4] specifies how to establish subscriptions to a
   homogeneous resource list in SIP [2] and defines the procedures for
   getting notifications about changes in the state of the associated
   resources.  Yet, list creation is outside the scope of [4].

   This document specifies a way to create a list with a set of
   resources and subscribe to it using a single SIP request.  This is
   achieved by including the list of resources (as defined in [5]) in
   the body of the SUBSCRIBE request.


2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [1] and indicate requirement levels for
   compliant implementations.


3.  Providing a Resource List Server with a URI-List

   A client that wants to create a resource list and subscribe to it
   using the mechanism described in this document, constructs a
   SUBSCRIBE with at least one body, whose disposition is type
   "recipient-list" as defined in [5], containing the URI-list.  The
   client MUST build the remaining of the SUBSCRIBE request following
   the rules in RFC 3265 [3].

   The client MUST support the "rlmi+xml" format defined in [4] and
   signal this by including "rlmi+xml" in the Accept header.  The client
   MAY support additional formats and include them in the Accept header
   field of the SUBSCRIBE.


4.  URI-List Format

   The [5] mandates that each URI-list services specification, such as
   the subscription service defined here, specifies the default format
   for the recipient-list bodies used within the particular service.

   The default format for the recipient-list bodies for the subscription
   service defined in this document is the resource list format defined
   in [6].  UAs (User Agents) and resource list servers handling
   recipient-list bodies MUST support this format and MAY support other
   formats.



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   The Extensible Markup Language (XML) Configuration Access Protocol
   (XCAP) resource list document provides features, such as hierarchical
   lists and the ability to include entries by reference relative to the
   XCAP root URI, that are not needed by the subscription service
   defined here, which only needs to transfer a flat list of URIs
   between a UA and the resource list server.  Therefore, when using the
   default resource list document, UAs SHOULD use flat lists (i.e., no
   hierarchical lists) and SHOULD NOT use <entry-ref> elements.

   A resource list server 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 resource
   list document.

   <?xml version="1.0" encoding="UTF-8"?>
   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
                  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <list>
       <entry uri="sip:bill@example.com" />
       <entry uri="sip:joe@example.org" />
       <entry uri="sip:ted@example.net" />
     </list>
   </resource-lists>

   Figure 1: URI-List


5.  Resource List Server Behavior

   On reception of a SUBSCRIBE with a URI-list, a resource list server,
   which chooses to accept the "rlmi+xml" format, MUST comply with [4]
   for creating the subscription and reporting the changes in the
   resources within the created dialog.

   Note that the status code in the response to the SUBSCRIBE does not
   provide any information about whether or not the resource list server
   was able to successfully subscribe to the URIs in the URI-list.  The
   client obtains this information in the notifications sent by the
   server.


6.  Subsequent SUBSCRIBEs

   The previous Sections have specified how to include a URI-list in an
   initial SUBSCRIBE request to a resource list server in order to
   subscribe to the state of a set of resources.  Once the subscription



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   has been created and a dialog between the client and the resource
   list server has been established, the client may need to send
   subsequent SUBSCRIBE requests to, for example, extend the duration of
   the subscription.

   At this point, there are no semantics associated with resource-list
   bodies in subsequent SUBSCRIBE requests (although future extensions
   may define them).  Therefore, clients SHOULD NOT include resource-
   list bodies in subsequent SUBSCRIBE requests to a resource list
   server.

   A resource list server receiving a subsequent SUBSCRIBE request with
   a resource-list body, following standard SIP procedures, rejects it
   with a 415 (Unsupported Media Type) response.

      Note that a difference between an initial SUBSCRIBE request and
      subsequent ones is that while the initial request is sent to the
      public URI of the resource list, subsequent ones are sent to the
      URI provided by the server when the dialog was established.
      Therefore, from the client'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.


7.  Option-tag

   This document defines the 'recipient-list-subscribe' option-tag for
   use in the Require and Supported SIP header fields.

   User agent clients generating a SUBSCRIBE with a recipient-list body,
   as described in previous sections, MUST include this option-tag in a
   Require header field.  User agents that are able to receive and
   process SUBSCRIBEs with a recipient-list body, as described in
   previous sections, SHOULD include this option-tag in a Supported
   header field when responding to OPTIONS requests.


8.  Providing a URI to Manipulate a Resource List

   A client may need to manipulate a resource list at a resource list
   server.  The resource list server MAY provide a URI to manipulate the
   resource list associated with a subscription using the Call-Info
   header field in the NOTIFY that establishes the subscription.  The
   "purpose" parameter of the Call-Info header field MUST have a value
   of 'list-management', which we register with the IANA in Section 11.
   The following is an example of such a header field.

   Call-Info: <http://xcap.example.com/your-list.xml>



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              ;purpose=list-management

   The life-time of a resource list to be manipulated by the URI
   provided by the server is blundled to the life-time of the
   subscription.  That is, the resource list SHOULD be destroyed when
   the subscription expires or is otherwise terminated.


9.  Example

   The following is an example of a SUBSCRIBE request, which carries a
   URI-list in its body, sent by a UA to a resource list server.

   SUBSCRIBE  sip:rls@example.com SIP/2.0
   Via: SIP/2.0/TCP terminal.example.com;branch=z9hG4bKwYb6QREiCL
   Max-Forwards: 70
   To: RLS <sip:rls@example.com>
   From: <sip:adam@example.com>;tag=ie4hbb8t
   Call-ID: cdB34qLToC@terminal.example.com
   CSeq: 1 SUBSCRIBE
   Contact: <sip:terminal.example.com>
   Event: presence
   Expires: 7200
   Require: recipient-list-subscribe
   Supported: eventlist
   Accept: application/cpim-pidf+xml
   Accept: application/rlmi+xml
   Accept: multipart/related
   Accept: multipart/signed
   Accept: multipart/encrypted
   Content-Type: application/resource-lists+xml
   Content-Disposition: recipient-list
   Content-Length: 337

   <?xml version="1.0" encoding="UTF-8"?>
   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
                  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <list>
       <entry uri="sip:bill@example.com" />
       <entry uri="sip:joe@example.org" />
       <entry uri="sip:ted@example.net" />
     </list>
   </resource-lists>

   Figure 2: SUBSCRIBE request






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10.  Security Considerations

   The Security Considerations Section of [4] discusses security issues
   related to resource list servers.  Resource list servers accepting
   request-contained URI-lists MUST also follow the security guidelines
   given in [4].

   The Framework and Security Considerations for SIP URI-List Services
   [5] discusses issues related to SIP URI-list services.  Given that a
   resource list server sending SUBSCRIBEs to a set of users acts as a
   URI-list service, implementations of resource list servers that
   handle request-contained URI-lists MUST follow the security-related
   rules in [5].  These rules include mandatory authentication and
   authorization of clients, and opt-in lists.


11.  IANA Considerations

   The document defines the 'list-management' value for the purpose
   parameter of the Call-Info header field.  A reference to this RFC (in
   double brackets) needs to be added to the purpose Call-Info parameter
   entry in the SIP Parameters registry.

   This document defines the 'recipient-list-subscribe' SIP option-tag
   in Section 7.  It should be registered in the Option Tags subregistry
   under the SIP parameter registry.  The following is the description
   to be used in the registration.

      This option-tag is used to ensure that a server can process the
      'recipient-list' body used in a SUBSCRIBE request.


12.  Acknowledges

   Cullen Jennings and Jonathan Rosenberg provided useful comments on
   this document.

13.  Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  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.

   [3]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
        Notification", RFC 3265, June 2002.



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   [4]  Roach, A., Campbell, B., and J. Rosenberg, "A Session Initiation
        Protocol (SIP) Event Notification Extension for Resource Lists",
        RFC 4662, August 2006.

   [5]  Camarillo, G. and A. Roach, "Framework and Security
        Considerations for Session Initiation Protocol (SIP)  Uniform
        Resource Identifier (URI)-List Services",
        draft-ietf-sipping-uri-services-05 (work in progress),
        January 2006.

   [6]  Rosenberg, J., "Extensible Markup Language (XML) Formats for
        Representing Resource Lists",
        draft-ietf-simple-xcap-list-usage-05 (work in progress),
        February 2005.





































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Authors' Addresses

   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com


   Adam Roach
   Estacado Systems

   Email: adam@estacado.net


   Orit Levin
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052

   Email: oritl@microsoft.com




























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