One document matched: draft-camarillo-sipping-adhoc-conferencing-00.txt

SIPPING Working Group                                       G. Camarillo
Internet-Draft                                                  Ericsson
Expires: September 25, 2004                                  A. Johnston
                                                                     MCI
                                                          March 27, 2004


      Ad-Hoc Conferencing in the Session Initiation Protocol (SIP)
           draft-camarillo-sipping-adhoc-conferencing-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

   This document describes how to create a conference using SIP ad-hoc
   methods and a URI list. In particular, we describe a mechanism that
   allows a client to provide a conference server with the initial list
   of participants for an ad-hoc conference.








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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. Example  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   7. Security Considerations  . . . . . . . . . . . . . . . . . . . . 5
   8. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . . 6
      Normative References . . . . . . . . . . . . . . . . . . . . . . 6
      Informational References . . . . . . . . . . . . . . . . . . . . 7
      Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
      Intellectual Property and Copyright Statements . . . . . . . . . 8





































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1. Introduction

   Section 4.5 of [3] describes how to create a conference using ad-hoc
   SIP [2] 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 [3].

   Some environments have tough requirements regarding conference
   establishment time. So, 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 [4].

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 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 MAY add a "list"
   parameter (defined in [4]) to the conference factory URI and MUST
   place the resulting URI in the Request-URI. The "list" parameter MUST
   contain a pointer to a URI list that contains the participants that
   the client wants the server to INVITE. The following is an example of
   a Request-URI with a "list" parameter.


   sip:conf-factory@example.com;list="cid:cn35t8jf02@example.com"


4. URI List Format

   As described in [4], the default format for URI lists in SIP is the
   XCAP resource list format [5]. Still, specific services need to
   describe which information clients should include in their URI lists,
   as described in [4].




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   Conferencing UAs SHOULD use flat lists (i.e., no hierarchical lists),
   SHOULD NOT use any entry's attributes but "uri", and SHOULD NOT
   include any elements inside entries but "display-name" elements.

   A conference factory application receiving a URI list with more
   information than what we have just described SHOULD discard all the
   extra information.

5. Conference Server Behavior

   On reception of an INVITE with a URI list as described in Section 3,
   a conference server MUST follow the rules described in [3] 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 [3] (e.g., using CPCP [6]).

   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 [3].

   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 [7].

6. Example

   The following is an example of an INVITE request, which carries a URI
   list in its body, sent by a UA to a conference factory application.


   INVITE sip:conf-fact@example.com;list=cid:cn35t8jf02@example.com SIP/2.0
   Via: SIP/2.0/TCP client.chicago.example.com
       ;branch=z9hG4bKhjhs8ass83
   Max-Forwards: 70
   To: Conf Factory <sip:conf-fact@example.com>
   From: Carol <sip:carol@chicago.example.com>;tag=32331
   Call-ID: d432fa84b4c76e66710
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,



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        SUBSCRIBE, NOTIFY
   Allow-Events: dialog
   Accept: application/sdp, message/sipfrag,
        application/resource-lists+xml
   Conten-Type: multipart/mixed;boundary="boundary1"
   Content-Length: xxx

   --boundary1
   Content-Type: application/sdp
   Content-Length: xxx

   v=0
   o=carol 2890844526 2890842807 IN IP4 chicago.example.com
   s=Example Subject
   c=IN IP4 192.0.0.1
   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-Length: 315
   Content-ID: <cn35t8jf02@example.com>

   <?xml version="1.0" encoding="UTF-8"?>
   <resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <list>
       <entry uri="sip:bill@example.com" />
       <entry uri="sip:joe@example.com" />
       <entry uri="sip:ted@example.com" />
       <entry uri="sip:bob@example.com" />
     </list>
   </resource-lists>
   --boundary1--

                        Figure 1: INVITE request


7. Security Considerations

   This document discusses ad-hoc setup of SIP conferences using a list.
   Both conferencing and lists 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



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   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. In some cases, the list of potential
   participants may need to be kept private.  The use of TLS transport
   or S/MIME can be used to prevent a third party from viewing this
   information. In addition, a focus may have policies that limit the
   number of participants in the list, as a very long list could be used
   in a denial of service attack to place a large burden on the focus to
   send a large number of INVITEs.  Other list related security
   considerations are discussed in the list framework document.

8. Acknowledges

   Cullen Jennings provided useful comments on this document.

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]  Johnston, A. and O. Levin, "Session Initiation Protocol Call
        Control - Conferencing for User Agents",
        draft-ietf-sipping-cc-conferencing-03 (work in progress),
        February 2004.

   [4]  Camarillo, G., "Providing a Session Initiation Protocol (SIP)
        Application Server with a  List of URIs",
        draft-camarillo-sipping-uri-list-01 (work in progress), February
        2004.

   [5]  Rosenberg, J., "An Extensible Markup Language (XML)
        Configuration Access Protocol (XCAP)  Usage for Presence Lists",
        draft-ietf-simple-xcap-list-usage-02 (work in progress),
        February 2004.

Informational References



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   [6]  Koskelainen, P. and H. Khartabil, "An Extensible Markup Language
        (XML) Configuration Access Protocol (XCAP)  Usage for Conference
        Policy Manipulation", draft-koskelainen-xcon-xcap-cpcp-usage-02
        (work in progress), February 2004.

   [7]  Rosenberg, J. and H. Schulzrinne, "A Session Initiation Protocol
        (SIP) Event Package for Conference State",
        draft-ietf-sipping-conference-package-03 (work in progress),
        February 2004.


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: alan.johnston@mci.com






















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