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2 Network Working Group P. Saint-Andre
3 Internet-Draft &yet
4 Intended status: Standards Track A. Houri
5 Expires: September 6, 2015 IBM
6 J. Hildebrand
7 Cisco Systems, Inc.
8 March 5, 2015
10 Interworking between the Session Initiation Protocol (SIP) and the
11 Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
12 draft-ietf-stox-im-13
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 September 6, 2015.
38 Copyright Notice
40 Copyright (c) 2015 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. Intended Audience . . . . . . . . . . . . . . . . . . . . . . 3
57 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
58 4. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . . 4
59 5. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . . 6
60 6. Message Size . . . . . . . . . . . . . . . . . . . . . . . . 8
61 7. Content Types . . . . . . . . . . . . . . . . . . . . . . . . 9
62 8. Internationalization Considerations . . . . . . . . . . . . . 9
63 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
64 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10
65 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
66 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
69 1. Introduction
71 In order to help ensure interworking between instant messaging (IM)
72 systems that conform to the instant messaging / presence requirements
73 [RFC2779], it is important to clearly define protocol mappings
74 between such systems. Within the IETF, work has proceeded on two
75 instant messaging technologies:
77 o Various extensions to the Session Initiation Protocol ([RFC3261])
78 for instant messaging, in particular the MESSAGE method extension
79 [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),
93 since that is how existing systems solve the interworking problem.
95 Both XMPP and IM-capable SIP systems enable entities to exchange
96 "instant messages". The term "instant message" usually refers to a
97 message sent between two entities for delivery in close to real time
98 (rather than a message that is stored and forwarded to the intended
99 recipient upon request). This document covers single messages only
100 (sometimes called "page-mode" messaging), since they form the lowest
101 common denominator for IM. Separate documents cover "session-mode"
102 instant messaging in the form of one-to-one chat sessions
103 [I-D.ietf-stox-chat], as well as multi-party chat sessions
104 [I-D.ietf-stox-groupchat]. In particular, session-mode instant
105 messaging supports several features that are not part of page-mode
106 instant messaging, such as a higher level of assurance regarding end-
107 to-end message delivery.
109 The architectural assumptions underlying such direct mappings are
110 provided in [RFC7247], including mapping of addresses and error
111 conditions. The mappings specified in this document cover basic
112 instant messaging functionality, i.e., the exchange of a single
113 instant message between a SIP user and an XMPP user in either
114 direction. Mapping of more advanced functionality is out of scope
115 for this document, but other documents in this "series" cover such
116 topics.
118 2. Intended Audience
120 The documents in this series are intended for use by software
121 developers who have an existing system based on one of these
122 technologies (e.g., SIP), and would like to enable communication from
123 that existing system to systems based on the other technology (e.g.,
124 XMPP). We assume that readers are familiar with the core
125 specifications for both SIP [RFC3261] and XMPP [RFC6120], with the
126 base document for this series [RFC7247], and with the following IM-
127 related specifications:
129 o Session Initiation Protocol (SIP) Extension for Instant Messaging
130 [RFC3428]
132 o Extensible Messaging and Presence Protocol: Instant Messaging and
133 Presence [RFC6121]
135 Note well that not all protocol-compliant messages are shown (such as
136 SIP 100 TRYING messages), in order to focus the reader on the
137 essential aspects of the protocol flows.
139 3. Terminology
141 A number of terms used here are explained in [RFC3261], [RFC3428],
142 [RFC6120], and [RFC6121].
144 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
145 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
146 "OPTIONAL" in this document are to be interpreted as described in
147 [RFC2119].
149 4. XMPP to SIP
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).
156 When the XMPP user Juliet wants to send an
157 instant message to Romeo, she interacts with her XMPP client, which
158 generates an XMPP stanza. The syntax of the
159 stanza, including required and optional elements and attributes, is
160 defined in [RFC6121] (for single instant messages, Section 5.1 of
161 [RFC6121] recommends that the value of the 'to' address be a "bare
162 JID" of the form "localpart@domainpart"). The following is an
163 example of such a stanza:
165 Example 1: XMPP user sends message
167 |
169 | Art thou not Romeo, and a Montague?
170 |
172 Upon receiving such a message stanza, the XMPP server needs to
173 determine the identity of the domainpart in the 'to' address, which
174 it does by following the procedures explained in Section 5 of
175 [RFC7247]. If the domain is a SIP domain, the XMPP server will hand
176 off the message stanza to an XMPP-to-SIP gateway that natively
177 communicates with IM-aware SIP servers.
179 The XMPP-to-SIP gateway is then responsible for translating the XMPP
180 message stanza into a SIP MESSAGE request from the XMPP user to the
181 SIP user:
183 Example 2: XMPP user sends message (SIP transformation)
185 | MESSAGE sip:romeo@example.net SIP/2.0
186 | Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
187 | Max-Forwards: 70
188 | To: sip:romeo@example.net
189 | From: ;tag=12345
190 | Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
191 | CSeq: 1 MESSAGE
192 | Content-Type: text/plain
193 | Content-Length: 35
194 |
195 | Art thou not Romeo, and a Montague?
197 The destination SIP server is responsible for delivering the message
198 to the intended recipient, and the recipient is responsible for
199 generating a response (e.g., 200 OK).
201 Example 3: SIP user agent indicates receipt of message
203 | SIP/2.0 200 OK
204 | Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
205 | From: sip:juliet@example.com;tag=12345
206 | To: sip:romeo@example.net;tag=vwxyz
207 | Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
208 | CSeq: 1 MESSAGE
209 | Content-Length: 0
211 As described in [RFC3428], a downstream proxy could fork a MESSAGE
212 request, but it would return only one 200 OK to the gateway.
214 Note: This document does not specify handling of the 200 OK by the
215 XMPP-to-SIP gateway (e.g., to enable message acknowledgements).
216 See [I-D.ietf-stox-chat] for a mapping of message acknowledgements
217 in the context of one-to-one chat sessions.
219 The mapping of XMPP syntax to SIP syntax MUST be as shown in the
220 following table.
222 Table 1: Message syntax mapping from XMPP to SIP
224 +-----------------------------+--------------------------+
225 | XMPP Element or Attribute | SIP Header or Contents |
226 +-----------------------------+--------------------------+
227 | | body of MESSAGE |
228 | | Subject |
229 | | Call-ID |
230 | from | From (1) |
231 | id | transaction identifer |
232 | to | To or Request-URI |
233 | type | (no mapping) (2) |
234 | xml:lang | Content-Language |
235 +-----------------------------+--------------------------+
237 1. As shown in the foregoing example and described in [RFC7247], the
238 XMPP-to-SIP gateway MUST map the bare JID
239 ("localpart@domainpart") of the XMPP sender to the SIP From
240 header and include the resourcepart of the full JID as the GRUU
241 portion [RFC5627] of the SIP URI.
243 2. Because there is no SIP header field that matches the meaning of
244 the XMPP message 'type' values ("normal", "chat", "groupchat",
245 "headline", "error"), no general mapping is possible here.
247 5. SIP to XMPP
249 As described in [RFC3428], a single instant message is a SIP MESSAGE
250 request sent from a SIP user agent to an intended recipient who is
251 most generally referenced by an Instant Message URI of the form
252 but who might be referenced by a SIP or SIPS URI of
253 the form or .
255 When the SIP user Romeo wants to send an
256 instant message to Juliet, he interacts with his SIP user agent,
257 which generates a SIP MESSAGE request. The syntax of the MESSAGE
258 request is defined in [RFC3428]. The following is an example of such
259 a request:
261 Example 4: SIP user sends message
263 | MESSAGE sip:juliet@example.com SIP/2.0
264 | Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
265 | Max-Forwards: 70
266 | To: sip:juliet@example.com
267 | From: sip:romeo@example.net;tag=vwxyz
268 | Call-ID: 9E97FB43-85F4-4A00-8751-1124FD4C7B2E
269 | CSeq: 1 MESSAGE
270 | Content-Type: text/plain
271 | Content-Length: 44
272 |
273 | Neither, fair saint, if either thee dislike.
275 Section 5 of [RFC3428] stipulates that a SIP User Agent presented
276 with an im: URI should resolve it to a sip: or sips: URI. Therefore
277 we assume that the Request-URI of a request received by an IM-capable
278 SIP-to-XMPP gateway will contain a sip: or sips: URI. Upon receiving
279 the MESSAGE, the SIP server needs to determine the identity of the
280 domain portion of the Request-URI or To header, which it does by
281 following the procedures explained in Section 5 of [RFC7247]. If the
282 domain is an XMPP domain, the SIP server will hand off the MESSAGE to
283 an associated SIP-to-XMPP gateway that natively communicates with
284 XMPP servers.
286 The SIP-to-XMPP gateway is then responsible for translating the
287 request into an XMPP message stanza from the SIP user to the XMPP
288 user and returning a SIP "200 OK" message to the sender:
290 Example 5: SIP user sends message (XMPP transformation)
292 |
294 | Neither, fair saint, if either thee dislike.
295 |
297 Note that the stanza handling rules specified in [RFC6121] allow the
298 receiving XMPP server to deliver a message stanza whose 'to' address
299 is a bare JID ("localpart@domainpart") to multiple connected devices.
300 This is similar to the "forking" of messages in SIP.
302 The mapping of SIP syntax to XMPP syntax MUST be as shown in the
303 following table.
305 Table 2: Message syntax mapping from SIP to XMPP
307 +--------------------------+-----------------------------+
308 | SIP Header or Contents | XMPP Element or Attribute |
309 +--------------------------+-----------------------------+
310 | Call-ID | |
311 | Content-Language | xml:lang |
312 | CSeq | (no mapping) |
313 | From | from (1) |
314 | Subject | |
315 | Request-URI or To | to |
316 | body of MESSAGE | |
317 | transaction identifier | id |
318 +--------------------------+-----------------------------+
320 1. As shown in the foregoing example and described in [RFC7247], if
321 the IM-capable SIP-to-XMPP gateway has information about the GRUU
322 [RFC5627] of the particular endpoint that sent the SIP message
323 then it MUST map the sender's address to a full JID
324 ("localpart@domainpart/resourcepart") in the 'from' attribute of
325 the XMPP stanza and include the GRUU as the resourcepart.
327 When transforming SIP pager-mode messages, an IM-capable SIP-to-XMPP
328 gateway MUST specify no XMPP 'type' attribute or, equivalently, a
329 'type' attribute whose value is "normal" [RFC6121].
331 See Section 7 of this document about the handling of SIP message
332 bodies that contain content types other than plain text.
334 6. Message Size
336 [RFC3428] specifies that (outside of a media session) the size of a
337 MESSAGE request is not allowed to exceed 1300 bytes. Although in
338 practice XMPP instant messages do not often exceed that size, neither
339 [RFC6120] nor [RFC6121] sets an upper limit on the size of XMPP
340 stanzas. However, XMPP server deployments usually do limit the size
341 of stanzas in order to help prevent denial of service attacks, and
342 [RFC6120] states that if a server sets a maximum stanza size then the
343 limit is not allowed to be less than 10,000 bytes. Because of this
344 mismatch, an XMPP-to-SIP gateway SHOULD return a
345 stanza error if an XMPP user attempts to send an XMPP message stanza
346 that would result in a SIP MESSAGE greater than 1300 bytes. Although
347 such a gateway might decide to "upgrade" from page mode to session
348 mode using the Message Session Relay Protocol (MSRP) and thus
349 treating the instant message as part of a chat session as described
350 in [I-D.ietf-stox-chat], such behavior is application-specific and
351 this document provides no guidelines for how to complete such an
352 upgrade.
354 7. Content Types
356 SIP requests of type MESSAGE are allowed to contain essentially any
357 content type. The recommended procedures for SIP-to-XMPP gateways to
358 use in handling these content types are as follows.
360 An IM-aware SIP-to-XMPP gateway MUST process SIP messages that
361 contain message bodies of type "text/plain" and MUST encapsulate such
362 message bodies as the XML character data of the XMPP element.
364 An IM-aware SIP-to-XMPP gateway SHOULD process SIP messages that
365 contain message bodies of type "text/html"; if so, a gateway MUST
366 transform the "text/html" content into XHTML content that conforms to
367 the XHTML-IM Integration Set specified in [XEP-0071].
369 Although an IM-aware SIP-to-XMPP gateway MAY process SIP messages
370 that contain message bodies of types other than "text/plain" and
371 "text/html", the handling of such content types is a matter of
372 implementation.
374 8. Internationalization Considerations
376 Both XMPP and SIP support the UTF-8 encoding [RFC3629] of Unicode
377 characters [UNICODE] within messages, along with tagging of the
378 language for a particular message (in XMPP via the 'xml:lang'
379 attribute and in SIP via the Content-Language header). Gateways MUST
380 map these language tagging mechanisms if they are present in the
381 original message. Several examples follow, using the "XML Notation"
382 [RFC3987] for Unicode characters outside the ASCII range.
384 Example 6: SIP user sends message
386 | MESSAGE sip:juliet@example.com SIP/2.0
387 | Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
388 | Max-Forwards: 70
389 | To: sip:juliet@example.com
390 | From: sip:romeo@example.net;tag=vwxyz
391 | Call-ID: 5A37A65D-304B-470A-B718-3F3E6770ACAF
392 | CSeq: 1 MESSAGE
393 | Content-Type: text/plain
394 | Content-Length: 45
395 | Content-Language: cs
396 |
397 | Nic z ob쎩ho, m쎡 d쒛vo spanil쎡,
398 | nenavid쎭얡-li jedno nebo druh쎩.
400 Example 7: SIP user sends message (XMPP transformation)
402 |
405 |
406 | Nic z ob쎩ho, m쎡 d쒛vo spanil쎡,
407 | nenavid쎭얡-li jedno nebo druh쎩.
408 |
409 |
411 9. IANA Considerations
413 This document requests no actions of IANA.
415 10. Security Considerations
417 Detailed security considerations for instant messaging protocols are
418 given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
419 also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
420 (see also [RFC6120]). The security considerations provided in
421 [RFC7247] also apply.
423 This document specifies methods for exchanging "page-mode" instant
424 messages through a gateway that translates between SIP and XMPP, and
425 [I-D.ietf-stox-chat] specifies such methods for "session-mode"
426 instant messaging between MSRP and XMPP. Such a gateway MUST be
427 compliant with the minimum security requirements of the textual chat
428 protocols for which it translates (i.e., SIP or MSRP and XMPP).
430 The addition of gateways to the security model of instant messaging
431 specified in [RFC2779] introduces some new risks. In particular,
432 end-to-end security properties (especially confidentiality and
433 integrity) between instant messaging clients that interface through a
434 gateway can be provided only if common formats are supported.
435 Specification of those common formats is out of scope for this
436 document. For instant messages, it is possible to use [RFC3862] and
437 [RFC3923], but those methods are not widely implemented. A more
438 widely implemented albeit unstandardized method for interoperable
439 end-to-end encryption would be Off-the-Record Messaging [OTR].
441 11. References
443 11.1. Normative References
445 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
446 Requirement Levels", BCP 14, RFC 2119, March 1997.
448 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
449 A., Peterson, J., Sparks, R., Handley, M., and E.
450 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
451 June 2002.
453 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
454 and D. Gurle, "Session Initiation Protocol (SIP) Extension
455 for Instant Messaging", RFC 3428, December 2002.
457 [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
458 Agent URIs (GRUUs) in the Session Initiation Protocol
459 (SIP)", RFC 5627, October 2009.
461 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
462 Protocol (XMPP): Core", RFC 6120, March 2011.
464 [RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
465 Protocol (XMPP): Instant Messaging and Presence", RFC
466 6121, March 2011.
468 [RFC7247] Saint-Andre, P., Houri, A., and J. Hildebrand,
469 "Interworking between the Session Initiation Protocol
470 (SIP) and the Extensible Messaging and Presence Protocol
471 (XMPP): Architecture, Addresses, and Error Handling", RFC
472 7247, May 2014.
474 [XEP-0071]
475 Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.
477 11.2. Informative References
479 [I-D.ietf-simple-cpim-mapping]
480 Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
481 Presence and Instant Messaging", draft-ietf-simple-cpim-
482 mapping-01 (work in progress), June 2002.
484 [I-D.ietf-stox-chat]
485 Saint-Andre, P. and S. Loreto, "Interworking between the
486 Session Initiation Protocol (SIP) and the Extensible
487 Messaging and Presence Protocol (XMPP): One-to-One Text
488 Chat Sessions", draft-ietf-stox-chat-11 (work in
489 progress), March 2015.
491 [I-D.ietf-stox-groupchat]
492 Saint-Andre, P., Corretge, S., and S. Loreto,
493 "Interworking between the Session Initiation Protocol
494 (SIP) and the Extensible Messaging and Presence Protocol
495 (XMPP): Groupchat", draft-ietf-stox-groupchat-11 (work in
496 progress), March 2015.
498 [OTR] Ian Goldberg, , "Off-the-Record Messaging", .
501 [RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
502 / Presence Protocol Requirements", RFC 2779, February
503 2000.
505 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
506 10646", STD 63, RFC 3629, November 2003.
508 [RFC3860] Peterson, J., "Common Profile for Instant Messaging
509 (CPIM)", RFC 3860, August 2004.
511 [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant
512 Messaging (CPIM): Message Format", RFC 3862, August 2004.
514 [RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and
515 Presence Protocol (XMPP) to Common Presence and Instant
516 Messaging (CPIM)", RFC 3922, October 2004.
518 [RFC3923] Saint-Andre, P., "End-to-End Signing and Object Encryption
519 for the Extensible Messaging and Presence Protocol
520 (XMPP)", RFC 3923, October 2004.
522 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
523 Identifiers (IRIs)", RFC 3987, January 2005.
525 [UNICODE] The Unicode Consortium, "The Unicode Standard, Version
526 7.0.0", 2014,
527 .
529 Appendix A. Acknowledgements
531 The authors wish to thank the following individuals for their
532 feedback: Mary Barnes, Dave Cridland, Dave Crocker, Adrian Georgescu,
533 Christer Holmberg, Saul Ibarra Corretge, Olle Johansson, Paul
534 Kyzivat, Salvatore Loreto, Daniel-Constantin Mierla, and Tory Patnoe.
536 Special thanks to Ben Campbell for his detailed and insightful
537 reviews.
539 Francis Dupont reviewed the document on behalf of the General Area
540 Review Team.
542 Spencer Dawkins, Stephen Farrell, and Barry Leiba provided helpful
543 input during IESG review.
545 The authors gratefully acknowledge the assistance of Markus Isomaki
546 and Yana Stamcheva as the working group chairs and Gonzalo Camarillo
547 and Alissa Cooper as the sponsoring Area Directors.
549 Peter Saint-Andre wishes to acknowledge Cisco Systems, Inc., for
550 employing him during his work on earlier versions of this document.
552 Authors' Addresses
554 Peter Saint-Andre
555 &yet
557 Email: peter@andyet.com
558 URI: https://andyet.com/
560 Avshalom Houri
561 IBM
562 Rorberg Building, Pekris 3
563 Rehovot 76123
564 Israel
566 Email: avshalom@il.ibm.com
568 Joe Hildebrand
569 Cisco Systems, Inc.
570 1899 Wynkoop Street, Suite 600
571 Denver, CO 80202
572 USA
574 Email: jhildebr@cisco.com