Network Working Group P. Saint-Andre
Internet-Draft Cisco Systems, Inc.
Intended status: Informational A. Houri
Expires: April 18, 2013 IBM
J. Hildebrand
Cisco Systems, Inc.
October 15, 2012
Interworking between the Session Initiation Protocol (SIP) and the
Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
draft-saintandre-sip-xmpp-im-02
Abstract
This document defines a bi-directional protocol mapping for the
exchange of single instant messages between the Session Initiation
Protocol (SIP) and the Extensible Messaging and Presence Protocol
(XMPP).
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on April 18, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Saint-Andre, et al. Expires April 18, 2013 [Page 1]
Internet-Draft SIP-XMPP Interworking: IM October 2012
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Instant Messages . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . 6
4. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Saint-Andre, et al. Expires April 18, 2013 [Page 2]
Internet-Draft SIP-XMPP Interworking: IM October 2012
1. Introduction
In order to help ensure interworking between instant messaging
systems that conform to the instant messaging / presence requirements
[RFC2779], it is important to clearly define protocol mappings
between such systems. Within the IETF, work has proceeded on two
instant messaging technologies:
o Various extensions to the Session Initiation Protocol ([RFC3261])
for instant messaging, as developed within the SIP for Instant
Messaging and Presence Leveraging Extensions (SIMPLE) Working
Group; the relevant specification for instant messaging is
[RFC3428]
o The Extensible Messaging and Presence Protocol (XMPP), which
consists of a formalization of the core XML streaming protocols
developed originally by the Jabber open-source community; the
relevant specifications are [RFC6120] for the XML streaming layer
and [RFC6121] for basic presence and instant messaging extensions
One approach to helping ensure interworking between these protocols
is to map each protocol to the abstract semantics described in
[RFC3860]; that is the approach taken by
[I-D.ietf-simple-cpim-mapping] and [RFC3922]. The approach taken in
this document is to directly map semantics from one protocol to
another (i.e., from SIP/SIMPLE to XMPP and vice-versa).
The architectural assumptions underlying such direct mappings are
provided in [I-D.saintandre-sip-xmpp-core], including mapping of
addresses and error condisions. The mappings specified in this
document cover basic instant messaging functionality, i.e., the
exchange of a single instant message between a SIP user and an XMPP
user in either direction. Mapping of more advanced functionality is
out of scope for this document, but other documents in this "series"
cover such topics.
2. Terminology
The 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
[RFC2119].
3. Instant Messages
Saint-Andre, et al. Expires April 18, 2013 [Page 3]
Internet-Draft SIP-XMPP Interworking: IM October 2012
3.1. Overview
Both XMPP and IM-aware SIP systems enable entities (often but not
necessarily human users) to send "instant messages" to other
entities. The term "instant message" usually refers to messages sent
between two entities for delivery in close to real time (rather than
messages that are stored and forwarded to the intended recipient upon
request). Generally there are three kinds of instant message:
o Single messages, which are sent from the sender to the recipient
outside the context of any one-to-one chat session or multi-user
text conference.
o Chat messages, which are sent from the sender to the recipient in
the context of a "messaging session" between the two entities.
o Groupchat messages, which are sent from a sender to multiple
recipients in the context of a text conference.
This document covers single messages only, since they form the
"lowest common denominator" for instant messaging on the Internet.
It is likely that future documents will address one-to-one chat
sessions and multi-user chat.
Instant messaging using XMPP message stanzas of type "normal" is
specified in [RFC6121]. Instant messaging using SIP requests of type
MESSAGE (often called "page-mode" messaging) is specified in
[RFC3428].
As described in [RFC6121], a single instant message is an XML
stanza of type "normal" sent over an XML stream (since
"normal" is the default for the 'type' attribute of the
stanza, the attribute is often omitted). In this document we will
assume that such a message is sent from an XMPP client to an XMPP
server over an XML stream negotiated between the client and the
server, and that the client is controlled by a human user (this is a
simplifying assumption introduced for explanatory purposes only; the
XMPP sender could be a bot-controlled client, a component such as a
workflow application, a server, etc.). Continuing the tradition of
Shakespeare examples in XMPP documentation, we will say that the XMPP
user has an XMPP address of .
As described in [RFC3428], a single instant message is a SIP MESSAGE
request sent from a SIP user agent to an intended recipient who is
most generally referenced by an Instant Message URI of the form
but who may be referenced by a SIP or SIPS URI of
the form or Here again we
introduce the simplifying assumption that the user agent is
controlled by a human user, whom we shall dub .
Saint-Andre, et al. Expires April 18, 2013 [Page 4]
Internet-Draft SIP-XMPP Interworking: IM October 2012
3.2. XMPP to SIP
When Juliet wants to send an instant message to Romeo, she interacts
with her XMPP client, which generates an XMPP stanza. The
syntax of the stanza, including required and optional
elements and attributes, is defined in [RFC6121]. The following is
an example of such a stanza:
Example: XMPP user sends message:
|
| Art thou not Romeo, and a Montague?
|
Upon receiving such a stanza, the XMPP server to which Juliet has
connected either delivers it to a local recipient (if the hostname in
the 'to' attribute matches one of the hostnames serviced by the XMPP
server) or attempts to route it to the foreign domain that services
the hostname in the 'to' attribute. Naturally, in this document we
assume that the hostname in the 'to' attribute is an IM-aware SIP
service hosted by a separate server. As specified in [RFC6121], the
XMPP server needs to determine the identity of the foreign domain,
which it does by performing one or more DNS SRV lookups [RFC2782].
For message stanzas, the order of lookups recommended by [RFC6121] is
to first try the "_xmpp-server" service as specified in [RFC6120] and
to then try the "_im" service as specified in [RFC3861]. Here we
assume that the first lookup will fail but that the second lookup
will succeed and return a resolution "_im._simple.example.net.",
since we have already assumed that the example.net hostname is
running a SIP instant messaging service. (Note: The XMPP server may
have previously determined that the foreign domain is a SIMPLE
server, in which case it would not need to perform the SRV lookups;
the caching of such information is a matter of implementation and
local service policy, and is therefore out of scope for this
document.)
Once the XMPP server has determined that the foreign domain is
serviced by a SIMPLE server, it must determine how to proceed. We
here assume that the XMPP server contains or has available to it an
XMPP-SIMPLE gateway. The XMPP server would then deliver the message
stanza to the XMPP-SIMPLE gateway.
The XMPP-SIMPLE gateway is then responsible for translating the XMPP
message stanza into a SIP MESSAGE request from the XMPP user to the
SIP user:
Saint-Andre, et al. Expires April 18, 2013 [Page 5]
Internet-Draft SIP-XMPP Interworking: IM October 2012
Example: XMPP user sends message (SIP transformation):
| MESSAGE sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
| Max-Forwards: 70
| From: sip:juliet@example.com;tag=49583
| To: sip:romeo@example.net
| Call-ID: Hr0zny9l3@example.com
| CSeq: 1 MESSAGE
| Content-Type: text/plain
| Content-Length: 35
|
| Art thou not Romeo, and a Montague?
The mapping of XMPP syntax elements to SIP syntax elements SHOULD be
as shown in the following table. (Mappings for elements not
mentioned are undefined.)
Table 4: Message syntax mapping from XMPP to SIP
+-----------------------------+--------------------------+
| XMPP Element or Attribute | SIP Header or Contents |
+-----------------------------+--------------------------+
| | body of MESSAGE |
| | Subject |
| | Call-ID |
| from | From |
| id | (no mapping) |
| to | To |
| type | (no mapping) |
| xml:lang | Content-Language |
+-----------------------------+--------------------------+
3.3. SIP to XMPP
When Romeo wants to send an instant message to Juliet, he interacts
with his SIP user agent, which generates a SIP MESSAGE request. The
syntax of the MESSAGE request is defined in [RFC3428]. The following
is an example of such a request:
Saint-Andre, et al. Expires April 18, 2013 [Page 6]
Internet-Draft SIP-XMPP Interworking: IM October 2012
Example: SIP user sends message:
| MESSAGE sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
| Max-Forwards: 70
| From: sip:romeo@example.net;tag=38594
| To: sip:juliet@example.com
| Call-ID: M4spr4vdu@example.net
| CSeq: 1 MESSAGE
| Content-Type: text/plain
| Content-Length: 44
|
| Neither, fair saint, if either thee dislike.
Section 5 of [RFC3428] stipulates that a SIP User Agent presented
with an im: URI should resolve it to a sip: or sips: URI. Therefore
we assume that the To header of a request received by a SIMPLE-XMPP
gateway will contain a sip: or sips: URI. The gateway SHOULD resolve
that address to an im: URI for SIP MESSAGE requests, then follow the
rules in [RFC3861] regarding the "_im" SRV service for the target
domain contained in the To header. If SRV address resolution fails
for the "_im" service, the gateway MAY attempt a lookup for the
"_xmpp-server" service as specified in [RFC6120] or MAY return an
error to the sender (the SIP "502 Bad Gateway" error seems most
appropriate; see [I-D.saintandre-sip-xmpp-core] for details). If SRV
address resolution succeeds, the gateway is responsible for
translating the request into an XMPP message stanza from the SIP user
to the XMPP user and returning a SIP "200 OK" message to the sender:
Example: SIP user sends message (XMPP transformation):
|
| Neither, fair saint, if either thee dislike.
|
The mapping of SIP syntax elements to XMPP syntax elements SHOULD be
as shown in the following table. (Mappings for elements not
mentioned in the foregoing table are undefined.)
Saint-Andre, et al. Expires April 18, 2013 [Page 7]
Internet-Draft SIP-XMPP Interworking: IM October 2012
Table 5: Message syntax mapping from SIP to XMPP
+--------------------------+-----------------------------+
| SIP Header or Contents | XMPP Element or Attribute |
+--------------------------+-----------------------------+
| Call-ID | |
| Content-Language | xml:lang |
| CSeq | (no mapping) |
| From | from |
| Subject | |
| To | to |
| body of MESSAGE | |
+--------------------------+-----------------------------+
Note: When transforming SIP page-mode messages, a SIMPLE-XMPP gateway
SHOULD specify no XMPP 'type' attribute or a 'type' attribute whose
value is "normal" (alternatively, the value of the 'type' attribute
MAY be "chat", although it SHOULD NOT be "headline" and MUST NOT be
"groupchat").
Note: See the Content Types (Section 4) of this document regarding
handling of SIP message bodies that contain content types other than
plain text.
4. Content Types
SIP requests of type MESSAGE may contain essentially any content
type. The recommended procedures for SIMPLE-to-XMPP gateways to use
in handling these content types are as follows.
A SIMPLE-to-XMPP gateway MUST process SIP messages that contain
message bodies of type "text/plain" and MUST encapsulate such message
bodies as the XML character data of the XMPP element.
A SIMPLE-to-XMPP gateway SHOULD process SIP messages that contain
message bodies of type "text/html"; if so, a gateway MUST transform
the "text/html" content into XHTML content that conforms to the XHTML
1.0 Integration Set specified in [XEP-0071].
A SIMPLE-to-XMPP gateway MAY process SIP messages that contain
message bodies of types other than "text/plain" and "text/html" but
handling of such content types is a matter of implementation.
5. Security Considerations
Detailed security considerations for instant messaging protocols are
Saint-Andre, et al. Expires April 18, 2013 [Page 8]
Internet-Draft SIP-XMPP Interworking: IM October 2012
given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
(see also [RFC6120]).
This document specifies methods for exchanging instant messages
information through a gateway that translates between SIP and XMPP.
Such a gateway MUST be compliant with the minimum security
requirements of the instant messaging protocols for which it
translates (i.e., SIP and XMPP). The addition of gateways to the
security model of instant messaging specified in [RFC2779] introduces
some new risks. In particular, end-to-end security properties
(especially confidentiality and integrity) between instant messaging
user agents that interface through a SIMPLE-XMPP gateway can be
provided only if common formats are supported. Specification of
those common formats is out of scope for this document, although it
is recommended to use [RFC3862] for instant messages.
[RFC2779] requires that conformant technologies shall include methods
for blocking communications from unwanted addresses. Such blocking
is the responsibility of conformant technology (e.g., XMPP or SIP)
and is out of scope for this memo.
6. IANA Considerations
This document requests no actions of IANA.
7. References
7.1. Normative References
[I-D.saintandre-sip-xmpp-core]
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-02 (work in
progress), October 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Saint-Andre, et al. Expires April 18, 2013 [Page 9]
Internet-Draft SIP-XMPP Interworking: IM October 2012
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002.
[RFC3861] Peterson, J., "Address Resolution for Instant Messaging
and Presence", RFC 3861, August 2004.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence",
RFC 6121, March 2011.
7.2. Informative References
[I-D.ietf-simple-cpim-mapping]
Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
Presence and Instant Messaging",
draft-ietf-simple-cpim-mapping-01 (work in progress),
June 2002.
[RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
/ Presence Protocol Requirements", RFC 2779,
February 2000.
[RFC3860] Peterson, J., "Common Profile for Instant Messaging
(CPIM)", RFC 3860, August 2004.
[RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant
Messaging (CPIM): Message Format", RFC 3862, August 2004.
[RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and
Presence Protocol (XMPP) to Common Presence and Instant
Messaging (CPIM)", RFC 3922, October 2004.
[XEP-0071]
Saint-Andre, P., "XHTML-IM", XSF XEP 0071, January 2006.
Saint-Andre, et al. Expires April 18, 2013 [Page 10]
Internet-Draft SIP-XMPP Interworking: IM October 2012
Authors' Addresses
Peter Saint-Andre
Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600
Denver, CO 80202
USA
Phone: +1-303-308-3282
Email: psaintan@cisco.com
Avshalom Houri
IBM
Building 18/D, Kiryat Weizmann Science Park
Rehovot 76123
Israel
Email: avshalom@il.ibm.com
Joe Hildebrand
Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600
Denver, CO 80202
USA
Email: jhildebr@cisco.com
Saint-Andre, et al. Expires April 18, 2013 [Page 11]