SIPPING Working Group G. Camarillo Internet-Draft Ericsson Updates: 3265 (if approved) A. Roach Expires: July 30, 2007 Estacado Systems O. Levin Microsoft Corporation January 26, 2007 Subscriptions to Request-Contained Resource Lists in the Session Initiation Protocol (SIP) draft-ietf-sip-uri-list-subscribe-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 30, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). 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 request. Instead of having a subscriber send a SUBSCRIBE request for each resource individually, Camarillo, et al. Expires July 30, 2007 [Page 1] Internet-Draft SUBSCRIBE-Contained Lists January 2007 the subscriber 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. User Agent Client Procedures . . . . . . . . . . . . . . . . . 3 3.1. Response Handling . . . . . . . . . . . . . . . . . . . . 3 3.2. Subsequent SUBSCRIBE Requests . . . . . . . . . . . . . . 4 4. URI-List Document Format . . . . . . . . . . . . . . . . . . . 4 5. Resource List Server Behavior . . . . . . . . . . . . . . . . 5 5.1. Subsequent SUBSCRIBE Requests . . . . . . . . . . . . . . 5 6. Providing a URI to Manipulate a Resource List . . . . . . . . 5 7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 9.1. List-management Purpose Parameter Value . . . . . . . . . 8 9.2. Recipient-list-subscribe Option-Tag . . . . . . . . . . . 8 10. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . 8 11. Normative References . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Camarillo, et al. Expires July 30, 2007 [Page 2] Internet-Draft SUBSCRIBE-Contained Lists January 2007 1. Introduction RFC 4662 [4] specifies how to establish subscriptions to a homogeneous resource list in SIP (which is specified in RFC 3261 [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 RFC 4662 [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 RFC xxxx [5]) in the body of the SUBSCRIBE request. 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 RFC 2119 [1]. 3. User Agent Client Procedures A UAC (User Agent Client) that wants to create a resource list and subscribe to it using the mechanism described in this document, constructs a SUBSCRIBE request with at least one body, whose disposition is type "recipient-list" as defined in RFC xxxx [5], containing the URI-list. Additionally, the UAC MUST include the 'recipient-list-subscribe' option-tag, which is registered with the IANA in Section 9, in a Require header field. The UAC MUST build the remaining of the SUBSCRIBE request following the rules in RFC 3265 [3]. The UAC MUST support the "rlmi+xml" format defined in RFC 4662 [4] and signal this by including "rlmi+xml" in the Accept header. The UAC MAY support additional formats and include them in the Accept header field of the SUBSCRIBE request. 3.1. Response Handling The status code in the response to the SUBSCRIBE request 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 UAC obtains this information in the notifications sent by the server. Camarillo, et al. Expires July 30, 2007 [Page 3] Internet-Draft SUBSCRIBE-Contained Lists January 2007 3.2. Subsequent SUBSCRIBE Requests 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 has been created and a dialog between the UAC and the resource list server has been established, the UAC can 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 can define them). Therefore, UACs SHOULD NOT include resource-list bodies in subsequent SUBSCRIBE requests to a resource list server. 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 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 RFC xxxx [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 RFC xxxx [6]. UAs (User Agents) generating recipient-list bodies MUST support this format and MAY support other formats. Resource list servers able to handle recipient-list bodies MUST support this format and MAY support other formats. 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 elements. A resource list server receiving a URI-list with more information than what has just been described MAY discard all the extra information. Camarillo, et al. Expires July 30, 2007 [Page 4] Internet-Draft SUBSCRIBE-Contained Lists January 2007 Figure 1 shows an example of a flat list that follows the resource list document. Figure 1: URI-List 5. Resource List Server Behavior Resource list servers that are able to receive and process SUBSCRIBE requests with a recipient-list body SHOULD include a 'recipient-list- subscribe' option-tag in a Supported header field when responding to OPTIONS requests. On reception of a SUBSCRIBE request with a URI-list, a resource list server, which chooses to accept the "rlmi+xml" format, MUST comply with RFC 4662 [4] for creating the subscription and reporting the changes in the resources within the created dialog. 5.1. Subsequent SUBSCRIBE Requests At this point, there are no semantics associated with resource-list bodies in subsequent SUBSCRIBE requests (although future extensions may define them). Therefore, 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. 6. Providing a URI to Manipulate a Resource List A UAC can 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 request 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 9. The following is an example of such a header field. Camarillo, et al. Expires July 30, 2007 [Page 5] Internet-Draft SUBSCRIBE-Contained Lists January 2007 Call-Info: ;purpose=list-management The life-time of a resource list to be manipulated by the URI provided by the server is bundled to the life-time of the subscription. That is, the resource list SHOULD be destroyed when the subscription expires or is otherwise terminated. Section 7.1 of RFC 3265 [3] does not list the Call-Info header field in the table of header fields NOTIFY requests can carry. This document updates that table so that the Call-Info header field can be optionally included in NOTIFY requests. 7. Example The following is an example of a SUBSCRIBE request, which carries a URI-list in its body, sent by a UAC to a resource list server. Camarillo, et al. Expires July 30, 2007 [Page 6] Internet-Draft SUBSCRIBE-Contained Lists January 2007 SUBSCRIBE sip:rls@example.com SIP/2.0 Via: SIP/2.0/TCP terminal.example.com;branch=z9hG4bKwYb6QREiCL Max-Forwards: 70 To: RLS From: ;tag=ie4hbb8t Call-ID: cdB34qLToC@terminal.example.com CSeq: 1 SUBSCRIBE Contact: 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 Figure 2: SUBSCRIBE request 8. Security Considerations The Security Considerations Section of RFC 4662 [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 RFC 4662 [4]. The Framework and Security Considerations for SIP URI-List Services (which is specified in RFC xxxx [5]) discusses issues related to SIP URI-list services. Given that a resource list server sending SUBSCRIBE requests 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 RFC xxxx [5]. These rules include mandatory authentication and Camarillo, et al. Expires July 30, 2007 [Page 7] Internet-Draft SUBSCRIBE-Contained Lists January 2007 authorization of clients, and opt-in lists. 9. IANA Considerations The following sections request the IANA to register the 'list- management' value for the purpose parameter of the Call-Info header field and the 'recipient-list-subscribe' SIP option-tag. 9.1. List-management Purpose Parameter Value This 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 existing purpose Call-Info parameter entry in the SIP Parameters registry. 9.2. Recipient-list-subscribe Option-Tag This document defines the SIP option tag "recipient-list-subscribe". The following row shall be added to the "Option Tags" section of the SIP Parameter Registry: +--------------------------+------------------------------+-----------+ | Name | Description | Reference | +--------------------------+------------------------------+-----------+ | recipient-list-subscribe | This option tag is used to | [RFCXXXX] | | | ensure that a server can | | | | process the 'recipient-list' | | | | body used in a SUBSCRIBE | | | | request. | | +---------------------------------------------------------+-----------+ Editor Note: [RFCXXXX] should be replaced with the designation of this document. 10. Acknowledges Cullen Jennings and Jonathan Rosenberg provided useful comments on this document. 11. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Camarillo, et al. Expires July 30, 2007 [Page 8] Internet-Draft SUBSCRIBE-Contained Lists January 2007 [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. [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-06 (work in progress), September 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. 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 Camarillo, et al. Expires July 30, 2007 [Page 9] Internet-Draft SUBSCRIBE-Contained Lists January 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 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 at http://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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Camarillo, et al. Expires July 30, 2007 [Page 10]