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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: 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