SIPPING Working Group G. Camarillo
Internet-Draft Ericsson
Expires: August 6, 2004 A. Roach
dynamicsoft
February 6, 2004
Providing a Session Initiation Protocol (SIP) Application Server with
a List of URIs
draft-camarillo-sipping-uri-list-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document describes how a user agent can provide an application
server with a list of URIs. The way the application server uses the
URIs in the list is service specific.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. URI Parameter vs. Header Field . . . . . . . . . . . . . . . . 3
4. The SIP and SIPS URI List Parameter . . . . . . . . . . . . . 4
5. Ad-Hoc List' Life Time . . . . . . . . . . . . . . . . . . . . 4
6. The Content-ID SIP Header Field . . . . . . . . . . . . . . . 4
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1 Ad-Hoc Conference . . . . . . . . . . . . . . . . . . . . . . 5
7.2 Presence List . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
Normative References . . . . . . . . . . . . . . . . . . . . . 8
Informational References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10
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1. Introduction
The need for exploders in SIP is described in [7]. Mechanisms to
invoke exploders in SIP need to meet the requirements listed there.
UAs need to have a means to provide application servers with a set of
URIs for certain services. For example, a UA creating a conference
needs to provide the conference server with the participants. The
same way, a UA requesting presence information from a set of users
needs to provide the resource list server with the URIs of the users
that belong to the list.
These lists are typically configured using out-of-band methods. For
instance, a UA can use XCAP [6] to create a list of URIs and to
associate this list with a SIP URI. It can, then, send a SIP request
(an INVITE or a SUBSCRIBE in our previous examples) to that SIP URI.
Still, there is a need to create lists of URIs in an ad-hoc way and
send them directly in a SIP message. We define a SIP and SIPS URI
paramerer called "list", which carries a URI. This URI is a pointer
to a URI list.
A UA creating a SIP request that needs to carry a URI list proceeds
this way. It places the URI list (e.g., an XCAP resource list [4]) in
a body part, and then, it adds a "list" parameter to the Request-URI.
This "list" parameter contains a Content-ID URL [2] that points to
the body part that carries the URI list.
Alternatively, the URI in the "list" parameter can point to an
external URI list (e.g., an http URI). In this case, the URI list
would not be carried in the SIP request.
The way the application server interprets the URI list received in
the request is service specific.
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. URI Parameter vs. Header Field
We have chosen to transport the pointer to the URI list in a URI
parameter rather than in a header field because, this way, the
Request-URI fully indentifies the service being invoked and all the
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recipients of the service. Using a header field instead would imply
that the Request-URI did not carry the list of the reciptiens.
Network administrators should note that they need to configure
proxies to route correctly Request-URIs that contain a "list"
parameter and are addressed to their domain.
4. The SIP and SIPS URI List Parameter
We define the "list" parameter for SIP and SIPS URIs. It MUST contain
a URI that points to a URI list. The XCAP resource list format [4]
MUST be supported; any other URI list formats MAY be supported. The
ABNF of the "list" parameter is:
list-param = "list=" absoluteURI
The following is an example of a SIP URI with a list parameter
pointing to a body part using a Content-ID URL [2]:
sip:group@example.com;list=cid:cn35t8jf02@example.com
The following is an example of a SIP URI with a list parameter
pointing to an external URI:
sip:group@example.com;list=http://xcap.example.com/lists/mylist.xml
5. Ad-Hoc List' Life Time
An application server that receives a request with a URI list (or a
pointer to it) creates a so called ad-hoc list, whose lifetime
depends on the service provided by the server.
Ad-Hoc lists created by requests that do not establish a dialog
usually expire immediately. Ad-Hoc lists created by requests that
establish a dialog usually expire when the dialog terminates.
6. The Content-ID SIP Header Field
The Content-ID MIME header field is defined in RFC 2045 [5]. We
define here the same header field to be used in SIP messages. Its
ABNF is:
Content-ID = "Content-ID" HCOLON msg-id
RFC 2822 [3] defines msg-id in Section 3.6.4.
The Content-ID value is used to uniquely identify a body or a body
part. The Content-ID header field MAY appear in any SIP request or
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response that contains a body.
7. Examples
This section shows how to use the list parameter to create an ad-hoc
conference and to subscribe to the presence information to a set of
users. These examples illustrate the usage of the "list" parameter.
They do not mandate how the previously mentioned services have to be
implemented.
7.1 Ad-Hoc Conference
Carol creates an ad-hoc conference by sending the INVITE request
shown in Figure 1. The list parameter in the Request-URI points to a
MIME body that carries the list of participants.
INVITE sip:ad-hoc@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: "Ad-Hoc Conferences" <sip:ad-hoc@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,
SUBSCRIBE, NOTIFY
Allow-Events: dialog
Accept: application/sdp, message/sipfrag,
application/resource-lists+xml
Conten-Type: multipart/mixed;boundary="boundary1"
Content-Length: 731
--boundary1
Content-Type: application/sdp
Content-Length: 160
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
m=video 20002 RTP/AVP 31
--boundary1
Content-Type: application/resource-lists+xml
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Content-Length: 367
Content-ID: <cn35t8jf02@example.com>
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list name="ad-hoc-1">
<entry name="1" uri="sip:bill@example.com" />
<entry name="2" uri="sip:joe@example.com" />
<entry name="3" uri="sip:ted@example.com" />
<entry name="4" uri="sip:bob@example.com" />
</list>
</resource-lists>
--boundary1--
Figure 1: INVITE request
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.chicago.example.com
;branch=z9hG4bKhjhs8ass83;received=192.0.2.4
To: "Ad-Hoc Conferences" <sip:ad-hoc@example.com>;tag=733413
From: Carol <sip:carol@chicago.example.com>;tag=32331
Call-ID: d432fa84b4c76e66710
CSeq: 1 INVITE
Contact: <sip:3402934234@example.com>;isfocus
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
SUBSCRIBE, NOTIFY
Allow-Events: dialog, conference
Accept: application/sdp, application/conference-info+xml,
application/resource-lists+xml, message/sipfrag
Supported: replaces, join
Content-Type: application/sdp
Content-Length: 312
v=0
o=focus431 2890844526 2890842807 IN IP4 ms5.conf.example.com
s=Example Subject
i=Example Conference Hosted by Example.com
u=http://conf.example.com/3402934234
e=3402934234@conf-help.example.com
p=+1-888-555-1212
c=IN IP4 ms5.conf.example.com
t=0 0
m=audio 49170 RTP/AVP 0
m=video 51372 RTP/AVP 31
Figure 2: 200 (OK) response
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The conference server responds with a 200 (OK) that carries the URI
for the conference in its Contact header field. If the UA wants to
obtain information about the status of the conference, for instance,
it will SUBSCRIBE to the conference package using this URI.
7.2 Presence List
Carol subscribes to the presence information of four of her friends
using the list parameter.
SUBSCRIBE sip:ad-hoc@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: "Ad-Hoc Presence List" <sip:ad-hoc@example.com>
From: Carol <sip:carol@chicago.example.com>;tag=32331
Call-ID: d432fa84b4c76e66710
CSeq: 1 INVITE
Contact: <sip:carol@client.chicago.example.com>
Require: eventlist
Event: presence
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
SUBSCRIBE, NOTIFY
Allow-Events: presence
Accept: application/sdp, message/sipfrag,
application/resource-lists+xml, application/rlmi+xml
Content-Type: application/resource-lists+xml
Content-Length: 367
Content-ID: <cn35t8jf02@example.com>
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list name="ad-hoc-1">
<entry name="1" uri="sip:bill@example.com" />
<entry name="2" uri="sip:joe@example.com" />
<entry name="3" uri="sip:ted@example.com" />
<entry name="4" uri="sip:bob@example.com" />
</list>
</resource-lists>
Figure 3: SUBSCRIBE request
8. Security Considerations
TBD.
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9. IANA Considerations
This document registers the "list" SIP and SIPS URI parameter, which
is described in Section 4. This parameter is to be added to the SIP
and SIPS URI parameter registry under http://www.iana.org/ TBD.
This document registers the Content-ID SIP header field, which is
described in Section 6. This header field is to be added to the
header field registry under http://www.iana.org/assignments/
sip-parameters.
Header Name: Content-ID
Compact Form: (none)
Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Levinson, E., "Content-ID and Message-ID Uniform Resource
Locators", RFC 2392, August 1998.
[3] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[4] Rosenberg, J., "An Extensible Markup Language (XML)
Configuration Access Protocol (XCAP) Usage for Presence Lists",
draft-ietf-simple-xcap-list-usage-01 (work in progress), October
2003.
Informational References
[5] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
[6] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", draft-ietf-simple-xcap-01
(work in progress), October 2003.
[7] Camarillo, G., "Requirements for Session Initiation Protocol
(SIP) Exploder Invocation", draft-camarillo-sipping-exploders-01
(work in progress), November 2003.
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Authors' Addresses
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
EMail: Gonzalo.Camarillo@ericsson.com
Adam Roach
dynamicsoft
5100 Tennyson Pkwy
Suite 1200
Plano, TX 75024
US
EMail: adam@dynamicsoft.com
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