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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-11) exists of draft-ietf-stox-core-00 -- Possible downref: Non-RFC (?) normative reference: ref. 'XEP-0071' Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). 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: 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