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2 Network Working Group P. Saint-Andre
3 Internet-Draft Cisco Systems, Inc.
4 Intended status: Informational A. Houri
5 Expires: April 18, 2013 IBM
6 J. Hildebrand
7 Cisco Systems, Inc.
8 October 15, 2012
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-02
14 Abstract
16 This document defines a bi-directional 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 April 18, 2013.
38 Copyright Notice
40 Copyright (c) 2012 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 This document may contain material from IETF Documents or IETF
54 Contributions published or made publicly available before November
55 10, 2008. The person(s) controlling the copyright in some of this
56 material may not have granted the IETF Trust the right to allow
57 modifications of such material outside the IETF Standards Process.
58 Without obtaining an adequate license from the person(s) controlling
59 the copyright in such materials, this document may not be modified
60 outside the IETF Standards Process, and derivative works of it may
61 not be created outside the IETF Standards Process, except to format
62 it for publication as an RFC or to translate it into languages other
63 than English.
65 Table of Contents
67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
69 3. Instant Messages . . . . . . . . . . . . . . . . . . . . . . . 3
70 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4
71 3.2. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . 5
72 3.3. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . 6
73 4. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 8
74 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
75 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
76 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
77 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
78 7.2. Informative References . . . . . . . . . . . . . . . . . . 10
79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
81 1. Introduction
83 In order to help ensure interworking between instant messaging
84 systems that conform to the instant messaging / presence requirements
85 [RFC2779], it is important to clearly define protocol mappings
86 between such systems. Within the IETF, work has proceeded on two
87 instant messaging technologies:
89 o Various extensions to the Session Initiation Protocol ([RFC3261])
90 for instant messaging, as developed within the SIP for Instant
91 Messaging and Presence Leveraging Extensions (SIMPLE) Working
92 Group; the relevant specification for instant messaging is
93 [RFC3428]
94 o The Extensible Messaging and Presence Protocol (XMPP), which
95 consists of a formalization of the core XML streaming protocols
96 developed originally by the Jabber open-source community; the
97 relevant specifications are [RFC6120] for the XML streaming layer
98 and [RFC6121] for basic presence and instant messaging extensions
100 One approach to helping ensure interworking between these protocols
101 is to map each protocol to the abstract semantics described in
102 [RFC3860]; that is the approach taken by
103 [I-D.ietf-simple-cpim-mapping] and [RFC3922]. The approach taken in
104 this document is to directly map semantics from one protocol to
105 another (i.e., from SIP/SIMPLE to XMPP and vice-versa).
107 The architectural assumptions underlying such direct mappings are
108 provided in [I-D.saintandre-sip-xmpp-core], including mapping of
109 addresses and error condisions. The mappings specified in this
110 document cover basic instant messaging functionality, i.e., the
111 exchange of a single instant message between a SIP user and an XMPP
112 user in either direction. Mapping of more advanced functionality is
113 out of scope for this document, but other documents in this "series"
114 cover such topics.
116 2. Terminology
118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
120 "OPTIONAL" in this document are to be interpreted as described in
121 [RFC2119].
123 3. Instant Messages
124 3.1. Overview
126 Both XMPP and IM-aware SIP systems enable entities (often but not
127 necessarily human users) to send "instant messages" to other
128 entities. The term "instant message" usually refers to messages sent
129 between two entities for delivery in close to real time (rather than
130 messages that are stored and forwarded to the intended recipient upon
131 request). Generally there are three kinds of instant message:
133 o Single messages, which are sent from the sender to the recipient
134 outside the context of any one-to-one chat session or multi-user
135 text conference.
136 o Chat messages, which are sent from the sender to the recipient in
137 the context of a "messaging session" between the two entities.
138 o Groupchat messages, which are sent from a sender to multiple
139 recipients in the context of a text conference.
141 This document covers single messages only, since they form the
142 "lowest common denominator" for instant messaging on the Internet.
143 It is likely that future documents will address one-to-one chat
144 sessions and multi-user chat.
146 Instant messaging using XMPP message stanzas of type "normal" is
147 specified in [RFC6121]. Instant messaging using SIP requests of type
148 MESSAGE (often called "page-mode" messaging) is specified in
149 [RFC3428].
151 As described in [RFC6121], a single instant message is an XML
152 stanza of type "normal" sent over an XML stream (since
153 "normal" is the default for the 'type' attribute of the
154 stanza, the attribute is often omitted). In this document we will
155 assume that such a message is sent from an XMPP client to an XMPP
156 server over an XML stream negotiated between the client and the
157 server, and that the client is controlled by a human user (this is a
158 simplifying assumption introduced for explanatory purposes only; the
159 XMPP sender could be a bot-controlled client, a component such as a
160 workflow application, a server, etc.). Continuing the tradition of
161 Shakespeare examples in XMPP documentation, we will say that the XMPP
162 user has an XMPP address of .
164 As described in [RFC3428], a single instant message is a SIP MESSAGE
165 request sent from a SIP user agent to an intended recipient who is
166 most generally referenced by an Instant Message URI of the form
167 but who may be referenced by a SIP or SIPS URI of
168 the form or Here again we
169 introduce the simplifying assumption that the user agent is
170 controlled by a human user, whom we shall dub .
172 3.2. XMPP to SIP
174 When Juliet wants to send an instant message to Romeo, she interacts
175 with her XMPP client, which generates an XMPP stanza. The
176 syntax of the stanza, including required and optional
177 elements and attributes, is defined in [RFC6121]. The following is
178 an example of such a stanza:
180 Example: XMPP user sends message:
182 |
184 | Art thou not Romeo, and a Montague?
185 |
187 Upon receiving such a stanza, the XMPP server to which Juliet has
188 connected either delivers it to a local recipient (if the hostname in
189 the 'to' attribute matches one of the hostnames serviced by the XMPP
190 server) or attempts to route it to the foreign domain that services
191 the hostname in the 'to' attribute. Naturally, in this document we
192 assume that the hostname in the 'to' attribute is an IM-aware SIP
193 service hosted by a separate server. As specified in [RFC6121], the
194 XMPP server needs to determine the identity of the foreign domain,
195 which it does by performing one or more DNS SRV lookups [RFC2782].
196 For message stanzas, the order of lookups recommended by [RFC6121] is
197 to first try the "_xmpp-server" service as specified in [RFC6120] and
198 to then try the "_im" service as specified in [RFC3861]. Here we
199 assume that the first lookup will fail but that the second lookup
200 will succeed and return a resolution "_im._simple.example.net.",
201 since we have already assumed that the example.net hostname is
202 running a SIP instant messaging service. (Note: The XMPP server may
203 have previously determined that the foreign domain is a SIMPLE
204 server, in which case it would not need to perform the SRV lookups;
205 the caching of such information is a matter of implementation and
206 local service policy, and is therefore out of scope for this
207 document.)
209 Once the XMPP server has determined that the foreign domain is
210 serviced by a SIMPLE server, it must determine how to proceed. We
211 here assume that the XMPP server contains or has available to it an
212 XMPP-SIMPLE gateway. The XMPP server would then deliver the message
213 stanza to the XMPP-SIMPLE gateway.
215 The XMPP-SIMPLE gateway is then responsible for translating the XMPP
216 message stanza into a SIP MESSAGE request from the XMPP user to the
217 SIP user:
219 Example: XMPP user sends message (SIP transformation):
221 | MESSAGE sip:romeo@example.net SIP/2.0
222 | Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
223 | Max-Forwards: 70
224 | From: sip:juliet@example.com;tag=49583
225 | To: sip:romeo@example.net
226 | Call-ID: Hr0zny9l3@example.com
227 | CSeq: 1 MESSAGE
228 | Content-Type: text/plain
229 | Content-Length: 35
230 |
231 | Art thou not Romeo, and a Montague?
233 The mapping of XMPP syntax elements to SIP syntax elements SHOULD be
234 as shown in the following table. (Mappings for elements not
235 mentioned are undefined.)
237 Table 4: Message syntax mapping from XMPP to SIP
239 +-----------------------------+--------------------------+
240 | XMPP Element or Attribute | SIP Header or Contents |
241 +-----------------------------+--------------------------+
242 | | body of MESSAGE |
243 | | Subject |
244 | | Call-ID |
245 | from | From |
246 | id | (no mapping) |
247 | to | To |
248 | type | (no mapping) |
249 | xml:lang | Content-Language |
250 +-----------------------------+--------------------------+
252 3.3. SIP to XMPP
254 When Romeo wants to send an instant message to Juliet, he interacts
255 with his SIP user agent, which generates a SIP MESSAGE request. The
256 syntax of the MESSAGE request is defined in [RFC3428]. The following
257 is an example of such a request:
259 Example: SIP user sends message:
261 | MESSAGE sip:juliet@example.com SIP/2.0
262 | Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
263 | Max-Forwards: 70
264 | From: sip:romeo@example.net;tag=38594
265 | To: sip:juliet@example.com
266 | Call-ID: M4spr4vdu@example.net
267 | CSeq: 1 MESSAGE
268 | Content-Type: text/plain
269 | Content-Length: 44
270 |
271 | Neither, fair saint, if either thee dislike.
273 Section 5 of [RFC3428] stipulates that a SIP User Agent presented
274 with an im: URI should resolve it to a sip: or sips: URI. Therefore
275 we assume that the To header of a request received by a SIMPLE-XMPP
276 gateway will contain a sip: or sips: URI. The gateway SHOULD resolve
277 that address to an im: URI for SIP MESSAGE requests, then follow the
278 rules in [RFC3861] regarding the "_im" SRV service for the target
279 domain contained in the To header. If SRV address resolution fails
280 for the "_im" service, the gateway MAY attempt a lookup for the
281 "_xmpp-server" service as specified in [RFC6120] or MAY return an
282 error to the sender (the SIP "502 Bad Gateway" error seems most
283 appropriate; see [I-D.saintandre-sip-xmpp-core] for details). If SRV
284 address resolution succeeds, the gateway is responsible for
285 translating the request into an XMPP message stanza from the SIP user
286 to the XMPP user and returning a SIP "200 OK" message to the sender:
288 Example: SIP user sends message (XMPP transformation):
290 |
292 | Neither, fair saint, if either thee dislike.
293 |
295 The mapping of SIP syntax elements to XMPP syntax elements SHOULD be
296 as shown in the following table. (Mappings for elements not
297 mentioned in the foregoing table are undefined.)
298 Table 5: Message syntax mapping from SIP to XMPP
300 +--------------------------+-----------------------------+
301 | SIP Header or Contents | XMPP Element or Attribute |
302 +--------------------------+-----------------------------+
303 | Call-ID | |
304 | Content-Language | xml:lang |
305 | CSeq | (no mapping) |
306 | From | from |
307 | Subject | |
308 | To | to |
309 | body of MESSAGE | |
310 +--------------------------+-----------------------------+
312 Note: When transforming SIP page-mode messages, a SIMPLE-XMPP gateway
313 SHOULD specify no XMPP 'type' attribute or a 'type' attribute whose
314 value is "normal" (alternatively, the value of the 'type' attribute
315 MAY be "chat", although it SHOULD NOT be "headline" and MUST NOT be
316 "groupchat").
318 Note: See the Content Types (Section 4) of this document regarding
319 handling of SIP message bodies that contain content types other than
320 plain text.
322 4. Content Types
324 SIP requests of type MESSAGE may contain essentially any content
325 type. The recommended procedures for SIMPLE-to-XMPP gateways to use
326 in handling these content types are as follows.
328 A SIMPLE-to-XMPP gateway MUST process SIP messages that contain
329 message bodies of type "text/plain" and MUST encapsulate such message
330 bodies as the XML character data of the XMPP element.
332 A SIMPLE-to-XMPP gateway SHOULD process SIP messages that contain
333 message bodies of type "text/html"; if so, a gateway MUST transform
334 the "text/html" content into XHTML content that conforms to the XHTML
335 1.0 Integration Set specified in [XEP-0071].
337 A SIMPLE-to-XMPP gateway MAY process SIP messages that contain
338 message bodies of types other than "text/plain" and "text/html" but
339 handling of such content types is a matter of implementation.
341 5. Security Considerations
343 Detailed security considerations for instant messaging protocols are
344 given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
345 also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
346 (see also [RFC6120]).
348 This document specifies methods for exchanging instant messages
349 information through a gateway that translates between SIP and XMPP.
350 Such a gateway MUST be compliant with the minimum security
351 requirements of the instant messaging protocols for which it
352 translates (i.e., SIP and XMPP). The addition of gateways to the
353 security model of instant messaging specified in [RFC2779] introduces
354 some new risks. In particular, end-to-end security properties
355 (especially confidentiality and integrity) between instant messaging
356 user agents that interface through a SIMPLE-XMPP gateway can be
357 provided only if common formats are supported. Specification of
358 those common formats is out of scope for this document, although it
359 is recommended to use [RFC3862] for instant messages.
361 [RFC2779] requires that conformant technologies shall include methods
362 for blocking communications from unwanted addresses. Such blocking
363 is the responsibility of conformant technology (e.g., XMPP or SIP)
364 and is out of scope for this memo.
366 6. IANA Considerations
368 This document requests no actions of IANA.
370 7. References
372 7.1. Normative References
374 [I-D.saintandre-sip-xmpp-core]
375 Saint-Andre, P., Houri, A., and J. Hildebrand,
376 "Interworking between the Session Initiation Protocol
377 (SIP) and the Extensible Messaging and Presence Protocol
378 (XMPP): Core", draft-saintandre-sip-xmpp-core-02 (work in
379 progress), October 2012.
381 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
382 Requirement Levels", BCP 14, RFC 2119, March 1997.
384 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
385 specifying the location of services (DNS SRV)", RFC 2782,
386 February 2000.
388 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
389 A., Peterson, J., Sparks, R., Handley, M., and E.
391 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
392 June 2002.
394 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
395 and D. Gurle, "Session Initiation Protocol (SIP) Extension
396 for Instant Messaging", RFC 3428, December 2002.
398 [RFC3861] Peterson, J., "Address Resolution for Instant Messaging
399 and Presence", RFC 3861, August 2004.
401 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
402 Protocol (XMPP): Core", RFC 6120, March 2011.
404 [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
405 Protocol (XMPP): Instant Messaging and Presence",
406 RFC 6121, March 2011.
408 7.2. Informative References
410 [I-D.ietf-simple-cpim-mapping]
411 Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
412 Presence and Instant Messaging",
413 draft-ietf-simple-cpim-mapping-01 (work in progress),
414 June 2002.
416 [RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
417 / Presence Protocol Requirements", RFC 2779,
418 February 2000.
420 [RFC3860] Peterson, J., "Common Profile for Instant Messaging
421 (CPIM)", RFC 3860, August 2004.
423 [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant
424 Messaging (CPIM): Message Format", RFC 3862, August 2004.
426 [RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and
427 Presence Protocol (XMPP) to Common Presence and Instant
428 Messaging (CPIM)", RFC 3922, October 2004.
430 [XEP-0071]
431 Saint-Andre, P., "XHTML-IM", XSF XEP 0071, January 2006.
433 Authors' Addresses
435 Peter Saint-Andre
436 Cisco Systems, Inc.
437 1899 Wynkoop Street, Suite 600
438 Denver, CO 80202
439 USA
441 Phone: +1-303-308-3282
442 Email: psaintan@cisco.com
444 Avshalom Houri
445 IBM
446 Building 18/D, Kiryat Weizmann Science Park
447 Rehovot 76123
448 Israel
450 Email: avshalom@il.ibm.com
452 Joe Hildebrand
453 Cisco Systems, Inc.
454 1899 Wynkoop Street, Suite 600
455 Denver, CO 80202
456 USA
458 Email: jhildebr@cisco.com