Internet DRAFT - draft-saintandre-sip-xmpp-im
draft-saintandre-sip-xmpp-im
Network Working Group P. Saint-Andre
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track A. Houri
Expires: October 06, 2013 IBM
J. Hildebrand
Cisco Systems, Inc.
April 04, 2013
Interworking between the Session Initiation Protocol (SIP) and the
Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
draft-saintandre-sip-xmpp-im-03
Abstract
This document defines a bidirectional 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 October 06, 2013.
Copyright Notice
Copyright (c) 2013 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 October 06, 2013 [Page 1]
Internet-Draft SIP-XMPP Interworking: IM April 2013
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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]. By contrast, 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).
Both XMPP and IM-aware SIP systems enable entities to exchange
"instant messages". 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). This document covers single messages only
Saint-Andre, et al. Expires October 06, 2013 [Page 2]
Internet-Draft SIP-XMPP Interworking: IM April 2013
(sometimes called "pager-mode" messaging), since they form the lowest
common denominator for instant messaging. One-to-one chat sessions
and multi-party groupchat are covered in separate documents.
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.
The discussion venue for this document is the mailing list of the
DISPATCH WG; visit https://www.ietf.org/mailman/listinfo/dispatch for
subscription information and discussion archives.
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. XMPP to SIP
As described in [RFC6121], a single instant message is an XML
<message/> stanza of type "normal" sent over an XML stream (since
"normal" is the default for the 'type' attribute of the <message/>
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 <juliet@example.com>.
When Juliet wants to send an instant message to Romeo, she interacts
with her XMPP client, which generates an XMPP <message/> stanza. The
syntax of the <message/> 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:
Saint-Andre, et al. Expires October 06, 2013 [Page 3]
Internet-Draft SIP-XMPP Interworking: IM April 2013
| <message from='juliet@example.com/balcony'
| to='romeo@example.net'>
| <body>Art thou not Romeo, and a Montague?</body>
| </message>
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 (such an architecture is described in
[I-D.saintandre-sip-xmpp-core]). 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:
Example: XMPP user sends message (SIP transformation):
Saint-Andre, et al. Expires October 06, 2013 [Page 4]
Internet-Draft SIP-XMPP Interworking: IM April 2013
| 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;gr=balcony
| 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/> | body of MESSAGE |
| <subject/> | Subject |
| <thread/> | Call-ID |
| from | From |
| id | (no mapping) |
| to | To |
| type | (no mapping) |
| xml:lang | Content-Language |
+-----------------------------+--------------------------+
4. SIP to XMPP
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
<im:user@domain> but who may be referenced by a SIP or SIPS URI of
the form <sip:user@domain> or <sips:user@domain>. Here again we
introduce the simplifying assumption that the user agent is
controlled by a human user, whom we shall dub <romeo@example.net>.
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 October 06, 2013 [Page 5]
Internet-Draft SIP-XMPP Interworking: IM April 2013
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;gr=orchard
| To: sip:juliet@example.com;gr=balcony
| 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 MUST either attempt a lookup for
the "_xmpp-server" service as specified in [RFC6120] or 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):
| <message from='romeo@example.net/orchard'
| to='juliet@example.com/balcony'>
| <body>Neither, fair saint, if either thee dislike.</body>
| </message>
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.)
Table 5: Message syntax mapping from SIP to XMPP
Saint-Andre, et al. Expires October 06, 2013 [Page 6]
Internet-Draft SIP-XMPP Interworking: IM April 2013
+--------------------------+-----------------------------+
| SIP Header or Contents | XMPP Element or Attribute |
+--------------------------+-----------------------------+
| Call-ID | <thread/> |
| Content-Language | xml:lang |
| CSeq | (no mapping) |
| From | from |
| Subject | <subject/> |
| To | to |
| body of MESSAGE | <body/> |
+--------------------------+-----------------------------+
Note: When transforming SIP pager-mode messages, a SIMPLE-XMPP
gateway SHOULD specify no XMPP 'type' attribute or, equivalently, a
'type' attribute whose value is "normal".
Note: See Section 5 of this document about the handling of SIP
message bodies that contain content types other than plain text.
5. Content Types
SIP requests of type MESSAGE are allowed to 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 <body/> 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].
Although a SIMPLE-to-XMPP gateway MAY process SIP messages that
contain message bodies of types other than "text/plain" and "text/
html", the handling of such content types is a matter of
implementation.
6. Security Considerations
Detailed security considerations for instant messaging protocols are
given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
(see also [RFC6120]).
Saint-Andre, et al. Expires October 06, 2013 [Page 7]
Internet-Draft SIP-XMPP Interworking: IM April 2013
This document specifies methods for exchanging instant messages
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 preferred to use
[RFC3862] for instant messages.
7. IANA Considerations
This document requests no actions of IANA.
8. References
8.1. 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-04 (work in
progress), April 2013.
[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.
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.
Saint-Andre, et al. Expires October 06, 2013 [Page 8]
Internet-Draft SIP-XMPP Interworking: IM April 2013
[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.
[XEP-0071]
Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.
8.2. 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.
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
Saint-Andre, et al. Expires October 06, 2013 [Page 9]
Internet-Draft SIP-XMPP Interworking: IM April 2013
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 October 06, 2013 [Page 10]
