Network Working Group P. Saint-Andre
Internet-Draft XMPP Standards Foundation
Intended status: Informational January 4, 2008
Expires: July 7, 2008
Interworking between the Session Initiation Protocol (SIP) and the
Extensible Messaging and Presence Protocol (XMPP): Media Sessions
draft-saintandre-sip-xmpp-media-00
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Copyright (C) The IETF Trust (2008).
Abstract
This document defines a bi-directional protocol mapping for use by
gateways that enable the exchange of media signalling messages
between systems that implement the Jingle extensions to the
Extensible Messaging and Presence Protocol (XMPP) and those that
implement the Session Initiation Protocol (SIP).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Jingle to SIP . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Syntax Mappings . . . . . . . . . . . . . . . . . . . . . 4
2.3. Sample Scenarios . . . . . . . . . . . . . . . . . . . . . 8
3. SIP to Jingle . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Security Considerations . . . . . . . . . . . . . . . . . . . 14
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. Normative References . . . . . . . . . . . . . . . . . . . 15
5.2. Informative References . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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1. Introduction
The Session Initiation Protocol [SIP] is a widely-deployed technology
for the management of media sessions (such as voice calls) over the
Internet. SIP itself provides a signalling channel (typically via
the User Datagram Protocol [UDP]), over which two or more parties can
exchange messages for the purpose of negotiating a media session that
uses a dedicated media channel such as the Real-time Transport
Protocol [RTP].
The Extensible Messaging and Presence Protocol [XMPP] also provides a
signalling channel, typically via the Transmission Control Protocol
[TCP]. Given the significant differences between XMPP and SIP, it is
difficult to combine the two technologies in a single user agent.
Therefore, developers wishing to add media session capabilities to
XMPP clients have defined an XMPP-specific negotiation protocol
called Jingle [JINGLE].
However, Jingle has been designed to easily map to SIP for
communication through gateways or other transformation mechanisms.
Therefore, consistent with existing specifications for mapping
between SIP and XMPP (see [SIP-XMPP] and other specifications in that
"series"), this document describes a bi-directional protocol mapping
for use by gateways that enable the exchange of media signalling
messages between systems that implement SIP and those that implement
the XMPP Jingle extensions.
Note: The capitalized key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC 2119 [TERMS].
2. Jingle to SIP
2.1. Overview
As mentioned, Jingle was designed in part to enable straightforward
protocol mapping between XMPP and SIP. However, given the
significantly different technology assumptions underlying XMPP and
SIP, Jingle is naturally different from SIP in several important
respects:
o Base SIP messages and headers use a plaintext format similar in
some ways to the Hypertext Transport Protocol [HTTP], whereas
Jingle messages are pure XML. Mappings between SIP headers and
Jingle message syntax are provided below.
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o The SIP payloads defining session semantics use the Session
Description Protocol [SDP], whereas the equivalent Jingle payloads
are defined as XML child elements of the Jingle
element. However, the Jingle specifications defining such child
elements specify mappings to SDP for all Jingle syntax, making the
mapping relatively straightforward.
o The SIP signalling channel is transported over UDP, whereas the
signalling channel for Jingle is XMPP over TCP. Mapping between
the transport layers typically happens within a gateway using
techniques below the application level, and therefore is not
addressed in this specification.
2.2. Syntax Mappings
2.2.1. Generic Jingle Syntax
Jingle is designed in a modular fashion, so that session description
data is generally carried in a payload within the generic Jingle
elements, i.e., the element and its child. The
following example illustrates this structure, where the XMPP stanza
is a request to initiate an audio session using RTP over a raw UDP
transport.
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In the foregoing example, the syntax and semantics of the
and elements are defined in [JINGLE], the syntax and
semantics of the element are defined in
[JINGLE-AUDIO], and the syntax and semantics of the
element are defined in [JINGLE-UDP]. Other elements
are defined in specifications for the appropriate application types
(see for example [JINGLE-VIDEO]) and other elements are
defined in the specifications for appropriate transport methods (see
for example [JINGLE-ICE], which defines an XMPP profile of [ICE]).
At the core Jingle layer, the following mappings are defined.
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+--------------------------------+--------------------------------+
| Jingle | SIP |
+--------------------------------+--------------------------------+
| 'action' | [ see next table ] |
+--------------------------------+--------------------------------+
| 'initiator' | [ no mapping ] |
+--------------------------------+--------------------------------+
| 'responder' | [ no mapping ] |
+--------------------------------+--------------------------------+
| 'sid' | local-part of Call-ID |
+--------------------------------+--------------------------------+
| local-part of 'initiator' | in SDP o= line |
+--------------------------------+--------------------------------+
| 'creator' | [ no mapping ] |
+--------------------------------+--------------------------------+
| 'name' | [ no mapping ] |
+--------------------------------+--------------------------------+
| 'profile' | in SDP m= line |
+--------------------------------+--------------------------------+
| 'senders' value of | a= line of sendrecv, recvonly, |
| both, initiator, or responder | or sendonly |
+--------------------------------+--------------------------------+
The 'action' attribute of the element has nine allowable
values. In general they should be mapped as shown in the following
table, with some exceptions as described herein.
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+-------------------+-----------------+
| Jingle Action | SIP Method |
+-------------------+-----------------+
| content-accept | INVITE response |
| | (1xx) |
+-------------------+-----------------+
| content-add | INVITE request |
+-------------------+-----------------+
| content-modify | INVITE request |
+-------------------+-----------------+
| content-remove | INVITE request |
+-------------------+-----------------+
| session-accept | INVITE response |
| | (1xx or 2xx) |
+-------------------+-----------------+
| session-info | [varies] |
+-------------------+-----------------+
| session-initiate | INVITE request |
+-------------------+-----------------+
| session-terminate | BYE |
+-------------------+-----------------+
| transport-info | [varies] |
+-------------------+-----------------+
2.2.2. Audio Application Format
A Jingle application format for audio exchange via RTP is specified
in [JINGLE-AUDIO]. This application format effectively maps to the
"RTP/AVP" profile specified in [RTP-AVP], where the media type is
"audio" and the specific mappings to SDP syntax are provided in
[JINGLE-AUDIO].
2.2.3. Video Application Format
A Jingle application format for video exchange via RTP is specified
in [JINGLE-VIDEO]. This application format effectively maps to the
"RTP/AVP" profile specified in [RTP-AVP], where the media type is
"audio" and the specific mappings to SDP syntax are provided in
[JINGLE-VIDEO].
2.2.4. Raw UDP Transport Method
A basic Jingle transport method for exchanging media over UDP is
specified in [JINGLE-UDP]. This transport method involves the
negotiation of an IP address and port only, and does not provide NAT
traversal. The Jingle 'ip' attribute maps to the connection-address
parameter of the SDP c= line and the 'port' attribute maps to the
port parameter of the SDP m= line.
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2.2.5. ICE-UDP Transport Method
A more advanced Jingle transport method for exchanging media over UDP
is specified in [JINGLE-ICE]. Under ideal conditions this transport
method provides NAT traversal by following the Interactive
Connectivity Exchange methodology specified in [ICE]. The relevant
SDP mappings are provided in [JINGLE-ICE].
2.3. Sample Scenarios
The following sections provide sample scenarios (or "call flows")
that illustrate the principles of interworking from Jingle to SIP.
These scenarios are not exhaustive.
2.3.1. Basic Voice Chat
The protocol flow for a basic voice chat for which an XMPP user
(juliet@example.com) is the iniator and a SIP user
(romeo@example.net) is the responder. The voice chat is consummated
through a gateway. To simplify the example, the transport method
negotiated is "raw user datagram protocol" as specified in
[JINGLE-UDP].
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INITIATOR ...XMPP... GATEWAY ...SIP... RESPONDER
| | |
| session-initiate | |
|----------------------->| |
| IQ-result (ack) | |
|<-----------------------| |
| | INVITE |
| |---------------------->|
| | 180 Ringing |
| |<----------------------|
| session-info (ringing) | |
|<-----------------------| |
| IQ-result (ack) | |
|----------------------->| |
| | 200 OK |
| |<----------------------|
| session-accept | |
|<-----------------------| |
| IQ-result (ack) | |
|----------------------->| |
| | ACK |
| |---------------------->|
| MEDIA SESSION |
|<==============================================>|
| | BYE |
| |<----------------------|
| session-terminate | |
|<-----------------------| |
| IQ-result (ack) | |
|----------------------->| |
| | 200 OK |
| |---------------------->|
| | |
The packet flow is as follows.
First the XMPP user sends a Jingle session-initiation request to the
SIP user.
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The gateway returns an XMPP IQ-result to the initiator on behalf of
the responder.
The gateway transforms the Jingle session-initiate action into a SIP
INVITE.
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INVITE sip:romeo@example.net SIP/2.0
Via: SIP/2.0/TCP client.example.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Juliet Capulet ;tag=t3hr0zny
To: Romeo Montague
Call-ID: 3848276298220188511@example.com
CSeq: 1 INVITE
Contact:
Content-Type: application/sdp
Content-Length: 184
v=0
o=alice 2890844526 2890844526 IN IP4 client.example.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:96 SPEEX/16000
a=rtpmap:97 SPEEX/8000
a=rtpmap:18 G729
The responder returns a SIP 180 Ringing message.
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP client.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: Juliet Capulet ;tag=t3hr0zny
To: Romeo Montague ;tag=v3rsch1kk3l1jk
Call-ID: 3848276298220188511@example.com
CSeq: 1 INVITE
Contact:
Content-Length: 0
The gateway transforms the ringing message into XMPP syntax.
The initiator returns an IQ-result acknowledging receipt of the
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ringing message, which is used only by the gateway and not
transformed into SIP syntax.
The responder sends a SIP 200 OK to the initiator.
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.example.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: Juliet Capulet ;tag=t3hr0zny
To: Romeo Montague ;tag=v3rsch1kk3l1jk
Call-ID: 3848276298220188511@example.com
CSeq: 1 INVITE
Contact:
Content-Type: application/sdp
Content-Length: 147
v=0
o=romeo 2890844527 2890844527 IN IP4 client.example.net
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:97 SPEEX/8000
a=rtpmap:18 G729/8000
The gateway transforms the 200 OK into a Jingle session-accept
action.
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If the payload types and transport candidate can be successfully used
by both parties, then the initiator acknowledges the session-accept
action.
The parties now begin to exchange media. In this case they would
exchange audio using the Speex codec at a clockrate of 8000 since
that is the highest-priority codec for the responder (as determined
by the XML order of the children).
The parties may continue the session as long as desired.
Eventually, one of the parties (in this case the responder)
terminates the session.
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BYE sip:juliet@client.example.com SIP/2.0
Via: SIP/2.0/TCP client.example.net:5060;branch=z9hG4bKnashds7
Max-Forwards: 70
From: Romeo Montague ;tag=8321234356
To: Juliet Capulet ;tag=9fxced76sl
Call-ID: 3848276298220188511@example.com
CSeq: 1 BYE
Content-Length: 0
The gateway transforms the SIP BYE into XMPP syntax.
The initiator returns an IQ-result acknowledging receipt of the
session termination, which is used only by the gateway and not
transformed into SIP syntax.
3. SIP to Jingle
To follow.
4. Security Considerations
Detailed security considerations for session management are given for
SIP in [SIP] and for XMPP in [JINGLE] (see also [XMPP]).
5. References
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5.1. Normative References
[ICE] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols",
draft-ietf-mmusic-ice-19 (work in progress), October 2007.
[JINGLE] Ludwig, S., Beda, J., Saint-Andre, P., McQueen, R., Egan,
S., and J. Hildebrand, "Jingle", XSF XEP 0166, June 2007.
[JINGLE-AUDIO]
Ludwig, S., Saint-Andre, P., Egan, S., and R. McQueen,
"Jingle Audio via RTP", XSF XEP 0167, November 2007.
[JINGLE-ICE]
Beda, J., Ludwig, S., Saint-Andre, P., Hildebrand, J., and
S. Egan, "Jingle ICE-UDP Transport Method", XSF XEP 0176,
November 2007.
[JINGLE-UDP]
Beda, J., Saint-Andre, P., Ludwig, S., Hildebrand, J., and
S. Egan, "Jingle Raw UDP Transport", XSF XEP 0177,
November 2007.
[JINGLE-VIDEO]
Saint-Andre, P. and M. Chen, "Jingle Video via RTP", XSF
XEP 0180, November 2007.
[RTP-AVP] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551,
July 2003.
[SDP] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[SIP] 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.
[SIP-XMPP]
Saint-Andre, P., Houri, A., and J. Hildebrand,
"Interworking between the Session Initiation Protocol
(SIP) and the Extensible Messaging and Presence Protocol
(XMPP): Core", draft-saintandre-sip-xmpp-core-00 (work in
progress), January 2008.
[TERMS] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, March 1997.
[XMPP] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
5.2. Informative References
[HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RTP] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[TCP] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
Author's Address
Peter Saint-Andre
XMPP Standards Foundation
P.O. Box 1641
Denver, CO 80201
USA
Email: stpeter@jabber.org
URI: https://stpeter.im/
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