SIPPING Working Group G. Camarillo Internet-Draft Ericsson Expires:
October 10, 2004April 24, 2006 A. Johnston MCI April 8, 2004October 21, 2005 Conference Establishment Using Request-Contained Lists in the Session Initiation Protocol (SIP) draft-ietf-sipping-uri-list-conferencing-03.txtdraft-ietf-sipping-uri-list-conferencing-04.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 October 10, 2004.April 24, 2006. Copyright Notice Copyright (C) The Internet Society (2004).(2005). Abstract This document describes how to create a conference using SIP URI-list services. In particular, it describes a mechanism that allows a client to provide a conference server with the initial list of participants using an INVITE-contained URI-list. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Providing a Conference Server with a URI-List . . . . . . . . 3 4. URI-List Format . . . . . . . . . . . . . . . . . . . . . . . 3 5. Conference Server Behavior . . . . . . . . . . . . . . . . . . 4 6. Re-INVITEs . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. Option-tag . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 11. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . 8 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 12.1. 9 12.1. Normative References . . . . . . . . . . . . . . . . . . 8 12.29 12.2. Informational References . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 9. . . 10 Intellectual Property and Copyright Statements . . . . . . . 10. . . 11 1. Introduction Section 4.5 of  describes how to create a conference using ad-hoc SIP  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). Once the client obtains the conference URI, it can add participants to the newly created conference in several ways, which are described in . Some environments have tough requirements regarding conference establishment time. They require the client to be able to request the creation of an ad-hoc conference and to provide the 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 . 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  and indicate requirement levels for compliant implementations. 3. Providing a Conference Server with a URI-List A client that wants to include the set of initial participants in its initial INVITE to create an ad-hoc conference, adds a body whose disposition type is recipient-list, as defined in , with a URI- list that contains the participants that the client wants the server to INVITE. The client sends this INVITE to the conference factory URI. 4. URI-List Format As described in , 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) and servers is the resource list format defined in . So, conferencing UAs and servers handling recipient-list bodies MUST support this format and MAY support other formats. Nevertheless, 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 conferencing service defined in this document, which only needs to transfer a flat list of URIs between a UA 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 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:email@example.com" /> <entry uri="sip:firstname.lastname@example.org" /> <entry uri="sip:email@example.com" /> </list> </resource-lists> Figure 1: URI-List 5. Conference Server Behavior On reception of an INVITE with a recipient-list body as described in Section 3, a conference server MUST follow the rules described in  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 . 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 . Note that the status code in the response to the INVITE 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) means that the conference was created successfully, that the client that generated the INVITE is in the conference, and that the server understood the URI-list. If the client wishes to obtain information about the status of other users in the conference it SHOULD use general conference mechanisms, such as the conference package . 6. Re-INVITEs 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 client and the conference server has been established, the client may need to send subsequent INVITE requests (typically referred to as re-INVITEs) 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 resource-list bodies in re-INVITEs (although future extensions may define them). Therefore, clients SHOULD NOT include resource-list bodies in re- INVITEs sent to a conference server. A conference server receiving a re-INVITE 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 INVITE request and a re- INVITE is that while the initial INVITE is sent to the conference factory URI, the re-INVITE is sent to the URI provided by the server in a Contact header field 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-invite' option-tag for use in the Require and Supported SIP header fields. User agent clients generating an INVITE 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 INVITEs 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. Note that according to Section 6, requests and responses coming from the URI of an ongoing conference would not carry this option- tag in a Supported header field. 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 this option-tag in, for example, responses to OPTIONS requests. 8. Example The following is an example of an INVITE request, which carries a URI-list in a recipient-list body part, sent by a UA to a conference factory application. Note that since the INVITE carries an SDP description as well, it contains a multipart body. INVITE sip:firstname.lastname@example.org SIP/2.0 Via: SIP/2.0/TCP client.chicago.example.com ;branch=z9hG4bKhjhs8ass83 Max-Forwards: 70 To: Conf Factory <sip:email@example.com> From: Carol <sip:firstname.lastname@example.org>;tag=32331 Call-ID: d432fa84b4c76e66710 CSeq: 1 INVITE Contact: <sip:email@example.com> Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY Allow-Events: dialog Accept: application/sdp, message/sipfrag Require: recipient-list-invite Conten-Type: multipart/mixed;boundary="boundary1" Content-Length: 690 --boundary1 Content-Type: application/sdp v=0 o=carol 2890844526 2890842807 IN IP4 chicago.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:xsi="http://www.w3.org/2001/XMLSchema-instance"> <list> <entry uri="sip:firstname.lastname@example.org" /> <entry uri="sip:email@example.com" /> <entry uri="sip:firstname.lastname@example.org" /> </list> </resource-lists> --boundary1-- Figure 2: INVITE request 9. Security Considerations This document discusses setup of SIP conferences using a request- contained URI-list. Both conferencing and URI-lists services have specific security requirements which will be summarized here. Conferences generally have authorization rules about who may or may not join a conference, what type of media may or may not 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. For conference creation using a list, there are some additional security considerations. The Framework and Security Considerations for SIP URI-List Services  discusses issues related to SIP URI- list services. Given that a conference server sending INVITEs to a set of users acts as an URI-list service, implementations of conference servers that handle lists MUST follow the security-related rules in . These rules include mandatory authentication and authorization of clients, and opt-in lists. 10. IANA Considerations This document defines the 'recipient-list-invite' 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 an INVITE request. 11. Acknowledges Cullen Jennings, Hisham Khartabil, and Jonathan Rosenberg provided useful comments on this document. 12. References 12.112.1. Normative References  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  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.  Johnston, A. and O. Levin, "Session Initiation Protocol Call Control - Conferencing for User Agents", draft-ietf-sipping-cc-conferencing-06draft-ietf-sipping-cc-conferencing-07 (work in progress), November 2004.June 2005.  Camarillo, G. and A. Roach, "Requirements and Framework for Session Initiation Protocol (SIP)Uniform Resource Identifier (URI)-List Services", draft-ietf-sipping-uri-services-02draft-ietf-sipping-uri-services-03 (work in progress), December 2004.April 2005.  Rosenberg, J., "Extensible Markup Language (XML) Formats for Representing Resource Lists", draft-ietf-simple-xcap-list-usage-05 (work in progress), February 2005. 12.212.2. Informational References  Rosenberg, J., "A Session Initiation Protocol (SIP) Event Package for Conference State", draft-ietf-sipping-conference-package-10draft-ietf-sipping-conference-package-12 (work in progress), MarchJuly 2005. Authors' Addresses Gonzalo Camarillo Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: Gonzalo.Camarillo@ericsson.com Alan Johnston MCI 100 South 4th Street St. Louis, MO 63102 USA Email: email@example.com Intellectual Property Statement 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 in BCP 78 and BCP 79. 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