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2 Network Working Group P. Saint-Andre
3 Internet-Draft Cisco Systems, Inc.
4 Intended status: Standards Track A. Houri
5 Expires: October 06, 2013 IBM
6 J. Hildebrand
7 Cisco Systems, Inc.
8 April 04, 2013
10 Interworking between the Session Initiation Protocol (SIP) and the
11 Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
12 draft-saintandre-sip-xmpp-im-03
14 Abstract
16 This document defines a bidirectional protocol mapping for the
17 exchange of single instant messages between the Session Initiation
18 Protocol (SIP) and the Extensible Messaging and Presence Protocol
19 (XMPP).
21 Status of This Memo
23 This Internet-Draft is submitted in full conformance with the
24 provisions of BCP 78 and BCP 79.
26 Internet-Drafts are working documents of the Internet Engineering
27 Task Force (IETF). Note that other groups may also distribute
28 working documents as Internet-Drafts. The list of current Internet-
29 Drafts is at http://datatracker.ietf.org/drafts/current/.
31 Internet-Drafts are draft documents valid for a maximum of six months
32 and may be updated, replaced, or obsoleted by other documents at any
33 time. It is inappropriate to use Internet-Drafts as reference
34 material or to cite them other than as "work in progress."
36 This Internet-Draft will expire on October 06, 2013.
38 Copyright Notice
40 Copyright (c) 2013 IETF Trust and the persons identified as the
41 document authors. All rights reserved.
43 This document is subject to BCP 78 and the IETF Trust's Legal
44 Provisions Relating to IETF Documents
45 (http://trustee.ietf.org/license-info) in effect on the date of
46 publication of this document. Please review these documents
47 carefully, as they describe your rights and restrictions with respect
48 to this document. Code Components extracted from this document must
49 include Simplified BSD License text as described in Section 4.e of
50 the Trust Legal Provisions and are provided without warranty as
51 described in the Simplified BSD License.
53 Table of Contents
55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
57 3. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . . 3
58 4. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . . 5
59 5. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 7
60 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
61 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
63 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
65 1. Introduction
67 In order to help ensure interworking between instant messaging
68 systems that conform to the instant messaging / presence requirements
69 [RFC2779], it is important to clearly define protocol mappings
70 between such systems. Within the IETF, work has proceeded on two
71 instant messaging technologies:
73 o Various extensions to the Session Initiation Protocol ([RFC3261])
74 for instant messaging, as developed within the SIP for Instant
75 Messaging and Presence Leveraging Extensions (SIMPLE) Working
76 Group; the relevant specification for instant messaging is
77 [RFC3428]
79 o The Extensible Messaging and Presence Protocol (XMPP), which
80 consists of a formalization of the core XML streaming protocols
81 developed originally by the Jabber open-source community; the
82 relevant specifications are [RFC6120] for the XML streaming layer
83 and [RFC6121] for basic presence and instant messaging extensions
85 One approach to helping ensure interworking between these protocols
86 is to map each protocol to the abstract semantics described in
87 [RFC3860]; that is the approach taken by
88 [I-D.ietf-simple-cpim-mapping] and [RFC3922]. By contrast, the
89 approach taken in this document is to directly map semantics from one
90 protocol to another (i.e., from SIP/SIMPLE to XMPP and vice-versa).
92 Both XMPP and IM-aware SIP systems enable entities to exchange
93 "instant messages". The term "instant message" usually refers to
94 messages sent between two entities for delivery in close to real time
95 (rather than messages that are stored and forwarded to the intended
96 recipient upon request). This document covers single messages only
97 (sometimes called "pager-mode" messaging), since they form the lowest
98 common denominator for instant messaging. One-to-one chat sessions
99 and multi-party groupchat are covered in separate documents.
101 The architectural assumptions underlying such direct mappings are
102 provided in [I-D.saintandre-sip-xmpp-core], including mapping of
103 addresses and error condisions. The mappings specified in this
104 document cover basic instant messaging functionality, i.e., the
105 exchange of a single instant message between a SIP user and an XMPP
106 user in either direction. Mapping of more advanced functionality is
107 out of scope for this document, but other documents in this "series"
108 cover such topics.
110 The discussion venue for this document is the mailing list of the
111 DISPATCH WG; visit https://www.ietf.org/mailman/listinfo/dispatch for
112 subscription information and discussion archives.
114 2. Terminology
116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
118 "OPTIONAL" in this document are to be interpreted as described in
119 [RFC2119].
121 3. XMPP to SIP
123 As described in [RFC6121], a single instant message is an XML
124 stanza of type "normal" sent over an XML stream (since
125 "normal" is the default for the 'type' attribute of the
126 stanza, the attribute is often omitted). In this document we will
127 assume that such a message is sent from an XMPP client to an XMPP
128 server over an XML stream negotiated between the client and the
129 server, and that the client is controlled by a human user (this is a
130 simplifying assumption introduced for explanatory purposes only; the
131 XMPP sender could be a bot-controlled client, a component such as a
132 workflow application, a server, etc.). Continuing the tradition of
133 Shakespeare examples in XMPP documentation, we will say that the XMPP
134 user has an XMPP address of .
136 When Juliet wants to send an instant message to Romeo, she interacts
137 with her XMPP client, which generates an XMPP stanza. The
138 syntax of the stanza, including required and optional
139 elements and attributes, is defined in [RFC6121]. The following is
140 an example of such a stanza:
142 Example: XMPP user sends message:
144 |
146 | Art thou not Romeo, and a Montague?
147 |
149 Upon receiving such a stanza, the XMPP server to which Juliet has
150 connected either delivers it to a local recipient (if the hostname in
151 the 'to' attribute matches one of the hostnames serviced by the XMPP
152 server) or attempts to route it to the foreign domain that services
153 the hostname in the 'to' attribute. Naturally, in this document we
154 assume that the hostname in the 'to' attribute is an IM-aware SIP
155 service hosted by a separate server. As specified in [RFC6121], the
156 XMPP server needs to determine the identity of the foreign domain,
157 which it does by performing one or more DNS SRV lookups [RFC2782].
158 For message stanzas, the order of lookups recommended by [RFC6121] is
159 to first try the "_xmpp-server" service as specified in [RFC6120] and
160 to then try the "_im" service as specified in [RFC3861]. Here we
161 assume that the first lookup will fail but that the second lookup
162 will succeed and return a resolution "_im._simple.example.net.",
163 since we have already assumed that the example.net hostname is
164 running a SIP instant messaging service. (Note: The XMPP server may
165 have previously determined that the foreign domain is a SIMPLE
166 server, in which case it would not need to perform the SRV lookups;
167 the caching of such information is a matter of implementation and
168 local service policy, and is therefore out of scope for this
169 document.)
171 Once the XMPP server has determined that the foreign domain is
172 serviced by a SIMPLE server, it must determine how to proceed. We
173 here assume that the XMPP server contains or has available to it an
174 XMPP-SIMPLE gateway (such an architecture is described in
175 [I-D.saintandre-sip-xmpp-core]). The XMPP server would then deliver
176 the message stanza to the XMPP-SIMPLE gateway.
178 The XMPP-SIMPLE gateway is then responsible for translating the XMPP
179 message stanza into a SIP MESSAGE request from the XMPP user to the
180 SIP user:
182 Example: XMPP user sends message (SIP transformation):
184 | MESSAGE sip:romeo@example.net SIP/2.0
185 | Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
186 | Max-Forwards: 70
187 | From: sip:juliet@example.com;gr=balcony
188 | To: sip:romeo@example.net
189 | Call-ID: Hr0zny9l3@example.com
190 | CSeq: 1 MESSAGE
191 | Content-Type: text/plain
192 | Content-Length: 35
193 |
194 | Art thou not Romeo, and a Montague?
196 The mapping of XMPP syntax elements to SIP syntax elements SHOULD be
197 as shown in the following table. (Mappings for elements not
198 mentioned are undefined.)
200 Table 4: Message syntax mapping from XMPP to SIP
202 +-----------------------------+--------------------------+
203 | XMPP Element or Attribute | SIP Header or Contents |
204 +-----------------------------+--------------------------+
205 | | body of MESSAGE |
206 | | Subject |
207 | | Call-ID |
208 | from | From |
209 | id | (no mapping) |
210 | to | To |
211 | type | (no mapping) |
212 | xml:lang | Content-Language |
213 +-----------------------------+--------------------------+
215 4. SIP to XMPP
217 As described in [RFC3428], a single instant message is a SIP MESSAGE
218 request sent from a SIP user agent to an intended recipient who is
219 most generally referenced by an Instant Message URI of the form
220 but who may be referenced by a SIP or SIPS URI of
221 the form or . Here again we
222 introduce the simplifying assumption that the user agent is
223 controlled by a human user, whom we shall dub .
225 When Romeo wants to send an instant message to Juliet, he interacts
226 with his SIP user agent, which generates a SIP MESSAGE request. The
227 syntax of the MESSAGE request is defined in [RFC3428]. The following
228 is an example of such a request:
230 Example: SIP user sends message:
232 | MESSAGE sip:juliet@example.com SIP/2.0
233 | Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
234 | Max-Forwards: 70
235 | From: sip:romeo@example.net;gr=orchard
236 | To: sip:juliet@example.com;gr=balcony
237 | Call-ID: M4spr4vdu@example.net
238 | CSeq: 1 MESSAGE
239 | Content-Type: text/plain
240 | Content-Length: 44
241 |
242 | Neither, fair saint, if either thee dislike.
244 Section 5 of [RFC3428] stipulates that a SIP User Agent presented
245 with an im: URI should resolve it to a sip: or sips: URI. Therefore
246 we assume that the To header of a request received by a SIMPLE-XMPP
247 gateway will contain a sip: or sips: URI. The gateway SHOULD resolve
248 that address to an im: URI for SIP MESSAGE requests, then follow the
249 rules in [RFC3861] regarding the "_im" SRV service for the target
250 domain contained in the To header. If SRV address resolution fails
251 for the "_im" service, the gateway MUST either attempt a lookup for
252 the "_xmpp-server" service as specified in [RFC6120] or return an
253 error to the sender (the SIP "502 Bad Gateway" error seems most
254 appropriate; see [I-D.saintandre-sip-xmpp-core] for details). If SRV
255 address resolution succeeds, the gateway is responsible for
256 translating the request into an XMPP message stanza from the SIP user
257 to the XMPP user and returning a SIP "200 OK" message to the sender:
259 Example: SIP user sends message (XMPP transformation):
261 |
263 | Neither, fair saint, if either thee dislike.
264 |
266 The mapping of SIP syntax elements to XMPP syntax elements SHOULD be
267 as shown in the following table. (Mappings for elements not
268 mentioned in the foregoing table are undefined.)
270 Table 5: Message syntax mapping from SIP to XMPP
271 +--------------------------+-----------------------------+
272 | SIP Header or Contents | XMPP Element or Attribute |
273 +--------------------------+-----------------------------+
274 | Call-ID | |
275 | Content-Language | xml:lang |
276 | CSeq | (no mapping) |
277 | From | from |
278 | Subject | |
279 | To | to |
280 | body of MESSAGE | |
281 +--------------------------+-----------------------------+
283 Note: When transforming SIP pager-mode messages, a SIMPLE-XMPP
284 gateway SHOULD specify no XMPP 'type' attribute or, equivalently, a
285 'type' attribute whose value is "normal".
287 Note: See Section 5 of this document about the handling of SIP
288 message bodies that contain content types other than plain text.
290 5. Content Types
292 SIP requests of type MESSAGE are allowed to contain essentially any
293 content type. The recommended procedures for SIMPLE-to-XMPP gateways
294 to use in handling these content types are as follows.
296 A SIMPLE-to-XMPP gateway MUST process SIP messages that contain
297 message bodies of type "text/plain" and MUST encapsulate such message
298 bodies as the XML character data of the XMPP element.
300 A SIMPLE-to-XMPP gateway SHOULD process SIP messages that contain
301 message bodies of type "text/html"; if so, a gateway MUST transform
302 the "text/html" content into XHTML content that conforms to the XHTML
303 1.0 Integration Set specified in [XEP-0071].
305 Although a SIMPLE-to-XMPP gateway MAY process SIP messages that
306 contain message bodies of types other than "text/plain" and "text/
307 html", the handling of such content types is a matter of
308 implementation.
310 6. Security Considerations
312 Detailed security considerations for instant messaging protocols are
313 given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
314 also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
315 (see also [RFC6120]).
317 This document specifies methods for exchanging instant messages
318 through a gateway that translates between SIP and XMPP. Such a
319 gateway MUST be compliant with the minimum security requirements of
320 the instant messaging protocols for which it translates (i.e., SIP
321 and XMPP). The addition of gateways to the security model of instant
322 messaging specified in [RFC2779] introduces some new risks. In
323 particular, end-to-end security properties (especially
324 confidentiality and integrity) between instant messaging user agents
325 that interface through a SIMPLE-XMPP gateway can be provided only if
326 common formats are supported. Specification of those common formats
327 is out of scope for this document, although it is preferred to use
328 [RFC3862] for instant messages.
330 7. IANA Considerations
332 This document requests no actions of IANA.
334 8. References
336 8.1. Normative References
338 [I-D.saintandre-sip-xmpp-core]
339 Saint-Andre, P., Houri, A., and J. Hildebrand,
340 "Interworking between the Session Initiation Protocol
341 (SIP) and the Extensible Messaging and Presence Protocol
342 (XMPP): Core", draft-saintandre-sip-xmpp-core-04 (work in
343 progress), April 2013.
345 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
346 Requirement Levels", BCP 14, RFC 2119, March 1997.
348 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
349 specifying the location of services (DNS SRV)", RFC 2782,
350 February 2000.
352 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
353 A., Peterson, J., Sparks, R., Handley, M., and E.
354 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
355 June 2002.
357 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
358 and D. Gurle, "Session Initiation Protocol (SIP) Extension
359 for Instant Messaging", RFC 3428, December 2002.
361 [RFC3861] Peterson, J., "Address Resolution for Instant Messaging
362 and Presence", RFC 3861, August 2004.
364 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
365 Protocol (XMPP): Core", RFC 6120, March 2011.
367 [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
368 Protocol (XMPP): Instant Messaging and Presence", RFC
369 6121, March 2011.
371 [XEP-0071]
372 Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.
374 8.2. Informative References
376 [I-D.ietf-simple-cpim-mapping]
377 Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
378 Presence and Instant Messaging", draft-ietf-simple-cpim-
379 mapping-01 (work in progress), June 2002.
381 [RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
382 / Presence Protocol Requirements", RFC 2779, February
383 2000.
385 [RFC3860] Peterson, J., "Common Profile for Instant Messaging
386 (CPIM)", RFC 3860, August 2004.
388 [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant
389 Messaging (CPIM): Message Format", RFC 3862, August 2004.
391 [RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and
392 Presence Protocol (XMPP) to Common Presence and Instant
393 Messaging (CPIM)", RFC 3922, October 2004.
395 Authors' Addresses
397 Peter Saint-Andre
398 Cisco Systems, Inc.
399 1899 Wynkoop Street, Suite 600
400 Denver, CO 80202
401 USA
403 Phone: +1-303-308-3282
404 Email: psaintan@cisco.com
405 Avshalom Houri
406 IBM
407 Building 18/D, Kiryat Weizmann Science Park
408 Rehovot 76123
409 Israel
411 Email: avshalom@il.ibm.com
413 Joe Hildebrand
414 Cisco Systems, Inc.
415 1899 Wynkoop Street, Suite 600
416 Denver, CO 80202
417 USA
419 Email: jhildebr@cisco.com