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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 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