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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: January 2, 2014 IBM
6 J. Hildebrand
7 Cisco Systems, Inc.
8 July 1, 2013
10 Interworking between the Session Initiation Protocol (SIP) and the
11 Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
12 draft-ietf-stox-im-00
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 January 2, 2014.
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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
57 3. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . . 4
58 4. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . . 6
59 5. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 8
60 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
61 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
63 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
64 8.2. Informative References . . . . . . . . . . . . . . . . . . 9
65 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 10
66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
68 1. Introduction
70 In order to help ensure interworking between instant messaging
71 systems that conform to the instant messaging / presence requirements
72 [RFC2779], it is important to clearly define protocol mappings
73 between such systems. Within the IETF, work has proceeded on two
74 instant messaging technologies:
76 o Various extensions to the Session Initiation Protocol ([RFC3261])
77 for instant messaging, as developed within the SIP for Instant
78 Messaging and Presence Leveraging Extensions (SIMPLE) Working
79 Group; the relevant specification for instant messaging is
80 [RFC3428]
81 o The Extensible Messaging and Presence Protocol (XMPP), which
82 consists of a formalization of the core XML streaming protocols
83 developed originally by the Jabber open-source community; the
84 relevant specifications are [RFC6120] for the XML streaming layer
85 and [RFC6121] for basic presence and instant messaging extensions
87 One approach to helping ensure interworking between these protocols
88 is to map each protocol to the abstract semantics described in
89 [RFC3860]; that is the approach taken by
90 [I-D.ietf-simple-cpim-mapping] and [RFC3922]. By contrast, the
91 approach taken in this document is to directly map semantics from one
92 protocol to another (i.e., from SIP/SIMPLE to XMPP and vice-versa).
94 Both XMPP and IM-aware SIP systems enable entities to exchange
95 "instant messages". The term "instant message" usually refers to
96 messages sent between two entities for delivery in close to real time
97 (rather than messages that are stored and forwarded to the intended
98 recipient upon request). This document covers single messages only
99 (sometimes called "pager-mode" messaging), since they form the lowest
100 common denominator for instant messaging. One-to-one chat sessions
101 and multi-party groupchat are covered in separate documents.
103 The architectural assumptions underlying such direct mappings are
104 provided in [I-D.ietf-stox-core], including mapping of addresses and
105 error condisions. The mappings specified in this document cover
106 basic instant messaging functionality, i.e., the exchange of a single
107 instant message between a SIP user and an XMPP user in either
108 direction. Mapping of more advanced functionality is out of scope
109 for this document, but other documents in this "series" cover such
110 topics.
112 The discussion venue for this document is the mailing list of the
113 STOX WG; visit https://www.ietf.org/mailman/listinfo/stox for
114 subscription information and discussion archives.
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. XMPP to SIP
125 As described in [RFC6121], a single instant message is an XML
126 stanza of type "normal" sent over an XML stream (since
127 "normal" is the default for the 'type' attribute of the
128 stanza, the attribute is often omitted). In this document we will
129 assume that such a message is sent from an XMPP client to an XMPP
130 server over an XML stream negotiated between the client and the
131 server, and that the client is controlled by a human user (this is a
132 simplifying assumption introduced for explanatory purposes only; the
133 XMPP sender could be a bot-controlled client, a component such as a
134 workflow application, a server, etc.). Continuing the tradition of
135 Shakespeare examples in XMPP documentation, we will say that the XMPP
136 user has an XMPP address of .
138 When Juliet wants to send an instant message to Romeo, she interacts
139 with her XMPP client, which generates an XMPP stanza. The
140 syntax of the stanza, including required and optional
141 elements and attributes, is defined in [RFC6121]. The following is
142 an example of such a stanza:
144 Example: XMPP user sends message:
146 |
148 | Art thou not Romeo, and a Montague?
149 |
151 Upon receiving such a stanza, the XMPP server to which Juliet has
152 connected either delivers it to a local recipient (if the hostname in
153 the 'to' attribute matches one of the hostnames serviced by the XMPP
154 server) or attempts to route it to the foreign domain that services
155 the hostname in the 'to' attribute. Naturally, in this document we
156 assume that the hostname in the 'to' attribute is an IM-aware SIP
157 service hosted by a separate server. As specified in [RFC6121], the
158 XMPP server needs to determine the identity of the foreign domain,
159 which it does by performing one or more DNS SRV lookups [RFC2782].
160 For message stanzas, the order of lookups recommended by [RFC6121] is
161 to first try the "_xmpp-server" service as specified in [RFC6120] and
162 to then try the "_im" service as specified in [RFC3861]. Here we
163 assume that the first lookup will fail but that the second lookup
164 will succeed and return a resolution "_im._simple.example.net.",
165 since we have already assumed that the example.net hostname is
166 running a SIP instant messaging service. (Note: The XMPP server may
167 have previously determined that the foreign domain is a SIMPLE
168 server, in which case it would not need to perform the SRV lookups;
169 the caching of such information is a matter of implementation and
170 local service policy, and is therefore out of scope for this
171 document.)
173 Once the XMPP server has determined that the foreign domain is
174 serviced by a SIMPLE server, it must determine how to proceed. We
175 here assume that the XMPP server contains or has available to it an
176 XMPP-SIMPLE gateway (such an architecture is described in
177 [I-D.ietf-stox-core]). The XMPP server would then deliver the
178 message stanza to the XMPP-SIMPLE gateway.
180 The XMPP-SIMPLE gateway is then responsible for translating the XMPP
181 message stanza into a SIP MESSAGE request from the XMPP user to the
182 SIP user:
184 Example: XMPP user sends message (SIP transformation):
186 | MESSAGE sip:romeo@example.net SIP/2.0
187 | Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
188 | Max-Forwards: 70
189 | To: sip:romeo@example.net
190 | From: sip:juliet@example.com
191 | Contact: sip:juliet@example.com;gr=balcony
192 | Call-ID: Hr0zny9l3@example.com
193 | CSeq: 1 MESSAGE
194 | Content-Type: text/plain
195 | Content-Length: 35
196 |
197 | Art thou not Romeo, and a Montague?
199 The mapping of XMPP syntax elements to SIP syntax elements SHOULD be
200 as shown in the following table. (Mappings for elements not
201 mentioned are undefined.)
202 Table 4: Message syntax mapping from XMPP to SIP
204 +-----------------------------+--------------------------+
205 | XMPP Element or Attribute | SIP Header or Contents |
206 +-----------------------------+--------------------------+
207 | | body of MESSAGE |
208 | | Subject |
209 | | Call-ID |
210 | from | From |
211 | id | (no mapping) |
212 | to | To |
213 | type | (no mapping) |
214 | xml:lang | Content-Language |
215 +-----------------------------+--------------------------+
217 4. SIP to XMPP
219 As described in [RFC3428], a single instant message is a SIP MESSAGE
220 request sent from a SIP user agent to an intended recipient who is
221 most generally referenced by an Instant Message URI of the form
222 but who may be referenced by a SIP or SIPS URI of
223 the form or . Here again we
224 introduce the simplifying assumption that the user agent is
225 controlled by a human user, whom we shall dub .
227 When Romeo wants to send an instant message to Juliet, he interacts
228 with his SIP user agent, which generates a SIP MESSAGE request. The
229 syntax of the MESSAGE request is defined in [RFC3428]. The following
230 is an example of such a request:
232 Example: SIP user sends message:
234 | MESSAGE sip:juliet@example.com SIP/2.0
235 | Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
236 | Max-Forwards: 70
237 | To: sip:juliet@example.com;gr=balcony
238 | From: sip:romeo@example.net
239 | Contact: sip:romeo@example.net;gr=orchard
240 | Call-ID: M4spr4vdu@example.net
241 | CSeq: 1 MESSAGE
242 | Content-Type: text/plain
243 | Content-Length: 44
244 |
245 | Neither, fair saint, if either thee dislike.
247 Section 5 of [RFC3428] stipulates that a SIP User Agent presented
248 with an im: URI should resolve it to a sip: or sips: URI. Therefore
249 we assume that the Request-URI of a request received by a SIMPLE-XMPP
250 gateway will contain a sip: or sips: URI. The gateway SHOULD resolve
251 that address to an im: URI for SIP MESSAGE requests, then follow the
252 rules in [RFC3861] regarding the "_im" SRV service for the target
253 domain contained in the Request-URI. If SRV address resolution fails
254 for the "_im" service, the gateway MUST either attempt a lookup for
255 the "_xmpp-server" service as specified in [RFC6120] or return an
256 error to the sender (the SIP "502 Bad Gateway" error seems most
257 appropriate; see [I-D.ietf-stox-core] for details). If SRV address
258 resolution succeeds, the gateway is responsible for translating the
259 request into an XMPP message stanza from the SIP user to the XMPP
260 user and returning a SIP "200 OK" message to the sender:
262 Example: SIP user sends message (XMPP transformation):
264 |
266 | Neither, fair saint, if either thee dislike.
267 |
269 The mapping of SIP syntax elements to XMPP syntax elements SHOULD be
270 as shown in the following table. (Mappings for elements not
271 mentioned in the foregoing table are undefined.)
273 Table 5: Message syntax mapping from SIP to XMPP
275 +--------------------------+-----------------------------+
276 | SIP Header or Contents | XMPP Element or Attribute |
277 +--------------------------+-----------------------------+
278 | Call-ID | |
279 | Content-Language | xml:lang |
280 | CSeq | (no mapping) |
281 | From | from |
282 | Subject | |
283 | Request-URI | to |
284 | body of MESSAGE | |
285 +--------------------------+-----------------------------+
287 Note: When transforming SIP pager-mode messages, a SIMPLE-XMPP
288 gateway SHOULD specify no XMPP 'type' attribute or, equivalently, a
289 'type' attribute whose value is "normal".
291 Note: See Section 5 of this document about the handling of SIP
292 message bodies that contain content types other than plain text.
294 5. Content Types
296 SIP requests of type MESSAGE are allowed to contain essentially any
297 content type. The recommended procedures for SIMPLE-to-XMPP gateways
298 to use in handling these content types are as follows.
300 A SIMPLE-to-XMPP gateway MUST process SIP messages that contain
301 message bodies of type "text/plain" and MUST encapsulate such message
302 bodies as the XML character data of the XMPP element.
304 A SIMPLE-to-XMPP gateway SHOULD process SIP messages that contain
305 message bodies of type "text/html"; if so, a gateway MUST transform
306 the "text/html" content into XHTML content that conforms to the XHTML
307 1.0 Integration Set specified in [XEP-0071].
309 Although a SIMPLE-to-XMPP gateway MAY process SIP messages that
310 contain message bodies of types other than "text/plain" and "text/
311 html", the handling of such content types is a matter of
312 implementation.
314 6. Security Considerations
316 Detailed security considerations for instant messaging protocols are
317 given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
318 also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
319 (see also [RFC6120]).
321 This document specifies methods for exchanging instant messages
322 through a gateway that translates between SIP and XMPP. Such a
323 gateway MUST be compliant with the minimum security requirements of
324 the instant messaging protocols for which it translates (i.e., SIP
325 and XMPP). The addition of gateways to the security model of instant
326 messaging specified in [RFC2779] introduces some new risks. In
327 particular, end-to-end security properties (especially
328 confidentiality and integrity) between instant messaging user agents
329 that interface through a SIMPLE-XMPP gateway can be provided only if
330 common formats are supported. Specification of those common formats
331 is out of scope for this document, although it is preferred to use
332 [RFC3862] for instant messages.
334 7. IANA Considerations
336 This document requests no actions of IANA.
338 8. References
339 8.1. Normative References
341 [I-D.ietf-stox-core]
342 Saint-Andre, P., Houri, A., and J. Hildebrand,
343 "Interworking between the Session Initiation Protocol
344 (SIP) and the Extensible Messaging and Presence Protocol
345 (XMPP): Core", draft-ietf-stox-core-00 (work in progress),
346 July 2013.
348 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
349 Requirement Levels", BCP 14, RFC 2119, March 1997.
351 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
352 specifying the location of services (DNS SRV)", RFC 2782,
353 February 2000.
355 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
356 A., Peterson, J., Sparks, R., Handley, M., and E.
357 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
358 June 2002.
360 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
361 and D. Gurle, "Session Initiation Protocol (SIP) Extension
362 for Instant Messaging", RFC 3428, December 2002.
364 [RFC3861] Peterson, J., "Address Resolution for Instant Messaging
365 and Presence", RFC 3861, August 2004.
367 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
368 Protocol (XMPP): Core", RFC 6120, March 2011.
370 [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
371 Protocol (XMPP): Instant Messaging and Presence",
372 RFC 6121, March 2011.
374 [XEP-0071]
375 Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.
377 8.2. Informative References
379 [I-D.ietf-simple-cpim-mapping]
380 Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
381 Presence and Instant Messaging",
382 draft-ietf-simple-cpim-mapping-01 (work in progress),
383 June 2002.
385 [RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
386 / Presence Protocol Requirements", RFC 2779,
387 February 2000.
389 [RFC3860] Peterson, J., "Common Profile for Instant Messaging
390 (CPIM)", RFC 3860, August 2004.
392 [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant
393 Messaging (CPIM): Message Format", RFC 3862, August 2004.
395 [RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and
396 Presence Protocol (XMPP) to Common Presence and Instant
397 Messaging (CPIM)", RFC 3922, October 2004.
399 Appendix A. Acknowledgements
401 The authors wish to thank the following individuals for their
402 feedback: Adrian Georgescu, Saul Ibarra, Salvatore Loreto, and Tory
403 Patnoe.
405 Authors' Addresses
407 Peter Saint-Andre
408 Cisco Systems, Inc.
409 1899 Wynkoop Street, Suite 600
410 Denver, CO 80202
411 USA
413 Phone: +1-303-308-3282
414 Email: psaintan@cisco.com
416 Avshalom Houri
417 IBM
418 Building 18/D, Kiryat Weizmann Science Park
419 Rehovot 76123
420 Israel
422 Email: avshalom@il.ibm.com
423 Joe Hildebrand
424 Cisco Systems, Inc.
425 1899 Wynkoop Street, Suite 600
426 Denver, CO 80202
427 USA
429 Email: jhildebr@cisco.com