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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BFCPBIS Working Group Ram. Ravindranath 3 Internet-Draft G. Salgueiro 4 Intended status: Standards Track Cisco 5 Expires: September 3, 2016 March 2, 2016 7 Session Description Protocol (SDP) WebSocket Connection URI Attribute 8 draft-ietf-bfcpbis-sdp-ws-uri-01 10 Abstract 12 The WebSocket protocol enables bidirectional real-time communication 13 between clients and servers in web-based applications. This document 14 specifies extensions to Session Description Protocol (SDP) for 15 application protocols using WebSocket as a transport. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on September 3, 2016. 34 Copyright Notice 36 Copyright (c) 2016 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 3. SDP Considerations . . . . . . . . . . . . . . . . . . . . . 3 54 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3.2. ws-uri SDP Attribute . . . . . . . . . . . . . . . . . . 3 56 3.3. wss-uri SDP Attribute . . . . . . . . . . . . . . . . . . 4 57 3.4. ws-uri and wss-uri Multiplexing Considerations . . . . . 4 58 4. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5 59 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 4.2. Generating the Initial Offer . . . . . . . . . . . . . . 5 61 4.3. Generating the Answer . . . . . . . . . . . . . . . . . . 6 62 4.4. Offerer Processing of the Answer . . . . . . . . . . . . 7 63 4.5. Modifying the Session . . . . . . . . . . . . . . . . . . 7 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 66 6.1. Registration of the 'ws-uri' SDP Media Attribute . . . . 8 67 6.2. Registration of the 'wss-uri' SDP Media Attribute . . . . 8 68 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 69 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 70 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 71 8.2. Informative References . . . . . . . . . . . . . . . . . 10 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 74 1. Introduction 76 The WebSocket protocol [RFC6455] enables bidirectional message 77 exchange between clients and servers on top of a persistent TCP 78 connection (optionally secured with Transport Layer Security (TLS) 79 [RFC5246]). The initial protocol handshake makes use of Hypertext 80 Transfer Protocol (HTTP) [RFC2616] semantics, allowing the WebSocket 81 protocol to reuse existing HTTP infrastructure. 83 Modern web browsers include a WebSocket client stack compliant with 84 the WebSocket API [WS-API] as specified by the W3C. It is expected 85 that other client applications (e.g., those running on personal 86 computers, mobile devices, etc.) will also make a WebSocket client 87 stack available. Several specifications have been written that 88 define how different applications can use a WebSocket subprotocol as 89 a reliable transport mechanism. 91 For example, [RFC7118] defines WebSocket subprotocol as a reliable 92 transport mechanism between Session Initiation Protocol 93 (SIP)[RFC3261] entities to enable use of SIP in web-oriented 94 deployments. Additionally, [I-D.pd-dispatch-msrp-websocket] defines 95 a new WebSocket sub-protocol as a reliable transport mechanism 96 between Message Session Relay Protocol (MSRP) clients and relays. 98 [RFC7395] defines a WebSocket subprotocol for the Extensible 99 Messaging and Presence Protocol (XMPP). Similarly, 100 [I-D.ietf-bfcpbis-bfcp-websocket] defines a WebSocket sub-protocol as 101 a reliable transport mechanism between Binary Floor Control Protocol 102 (BFCP) [I-D.ietf-bfcpbis-rfc4582bis] entities to enable usage of BFCP 103 in new scenarios. 105 As defined in Section 3 of [RFC2818], when using Secure WebSockets 106 the Canonical Name (CNAME) of the Secure Sockets Layer (SSL) 107 [RFC6101] certificate MUST match the WebSocket connection URI host. 108 While it is possible to generate self-signed certificates with 109 Internet Providers (IPs) as CNAME, in most cases it is not viable for 110 certificates signed by well known authorities. Thus, there is a need 111 to indicate the connection URI for the WebSocket Client. For 112 applications that use Session Description Protocol (SDP) [RFC4566] to 113 negotiate, the connection URI can be indicated by means of an SDP 114 attribute. This specification defines new SDP attributes to indicate 115 the connection URI for the WebSocket client. Applications that use 116 SDP for negotiation and WebSocket as a transport protocol can use 117 this specification to advertise the WebSocket client connection URI. 119 2. Terminology 121 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 122 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 123 document are to be interpreted as described in [RFC2119]. 125 3. SDP Considerations 127 3.1. General 129 Applications that use the SDP Offer/Answer mechanism [RFC3264] for 130 negotiating media and also use WebSocket as a transport protocol MAY 131 indicate the connection URI for the WebSocket Client via a new SDP a= 132 media-level attribute defined in Section 3.2. 134 Applications that use SDP for negotiation and also use secure 135 WebSocket as a transport protocol TLS MAY indicate the connection URI 136 for the WebSocket Client via a new SDP a= media-level attribute 137 defined in Section 3.3. 139 3.2. ws-uri SDP Attribute 141 This section defines a new SDP media-level attribute, 'ws-uri' which 142 can appear in any of the media lines. 144 Example: 146 a=ws-uri:ws://example.com/chat 148 Where "ws://example.com/chat" is the ws-URI defined in Section 3 of 149 [RFC6455]. 151 When the 'ws-uri' attribute is present in the media section of the 152 SDP, the IP address in 'c= ' line SHALL be ignored and the full URI 153 SHALL be used instead to open the WebSocket connection. The port 154 provided in the 'm= ' line SHALL be ignored too, as the 'a=ws-uri' 155 SHALL provide port number when needed. 157 3.3. wss-uri SDP Attribute 159 This section defines a new SDP media-level attribute, 'wss-uri' which 160 can appear in any of the media lines. 162 Example: 164 a=wss-uri:wss://example.com/chat 166 [Where "wss://example.com/chat" is the wss-URI defined in Section 3 167 of [RFC6455].] 169 When the 'wss-uri' attribute is present in the media section of the 170 SDP, the IP address in 'c= ' line SHALL be ignored and the full URI 171 SHALL be used instead to open the secure WebSocket connection. The 172 port provided in the 'm= ' line SHALL be ignored too, as the 'a=wss- 173 uri' SHALL provide port number when needed. 175 3.4. ws-uri and wss-uri Multiplexing Considerations 177 Multiplexing characteristics of SDP attributes are described in 178 [I-D.ietf-mmusic-sdp-mux-attributes]. Various SDP attribute 179 multiplexing categories are introduced there. 181 o The multiplexing category of the "a=ws-uri:" attribute is NOT 182 RECOMMENDED. 184 o The multiplexing category of the "a=ws-uri:" attribute is NOT 185 RECOMMENDED. 187 There are no multiplexing rules specified for the ws-uri and wss-uri 188 SDP media-level attributes. Additionally, the specification of 189 multiplexing rules for the ws-uri and wss-uri attributes is outside 190 the scope of this document. 192 While it is technically possible to bundle WebSocket, there are a 193 variety of reasons that make it impractical and it is thus considered 194 unlikely to be used in practice. Therefore, the ws-uri and wss-uri 195 SDP media-level attributes defined in Section 3.2 and Section 3.3 for 196 using WebSocket as a transport protocol are not likely to be used 197 with SDP bundle and are consequently categorized as NOT RECOMMENDED 198 for multiplexing. 200 If future extensions define how to bundle WebSocket then multiplexing 201 rules for the "a=ws-uri:" and "a=wss-uri:" attributes need to be 202 defined as well, for instance in an extension of this SDP based 203 WebSocket negotiation specification. 205 4. SDP Offer/Answer Procedures 207 4.1. General 209 An endpoint (i.e., both the offerer and the answerer) that wishes to 210 negotiate WebSocket as transport protocol MUST indicate that it 211 wishes to use WebSocket or secureWebSocket in the "proto" field of 212 the "m=" line. Furthermore, the SDP answerer MUST add an "a=ws-uri" 213 or "a=wss-uri" attribute in the "m=" line of each media-line 214 depending on whether the "proto" field has WebSocket or 215 secureWebSocket. This new attribute MUST follow the syntax defined 216 in Section 3. The procedures in this section apply to an "m=" line 217 associated with any media stream that uses WebSocket or 218 secureWebSocket as transport. 220 4.2. Generating the Initial Offer 222 An SDP offerer in order to negotiate WebSocket as a transport MUST 223 indicate the same in the "proto" field of the "m=" line. For 224 example, to negotiate BFCP-over-WebSocket the "proto" value in the 225 "m=" line MUST be TCP/WSS/BFCP if WebSocket is over TLS, else it MUST 226 be TCP/WS/BFCP. 228 The offerer SHOULD assign the SDP "setup" attribute with a value of 229 "active" (the offerer will be the initiator of the outgoing TCP 230 connection), unless the offerer insists on being a receiver of an 231 incoming connection, in which case the offerer SHOULD use a value of 232 "passive". The offerer MUST NOT assign an SDP "setup" attribute with 233 a "holdconn" value. If the offerer assigns the SDP "setup" attribute 234 with a value of "passive", the offerer MUST be prepared to receive an 235 incoming TCP connection on the IP and port tuple advertised in the 236 "c=" line and audio/video ports of the BFCP media stream before it 237 receives the SDP answer. 239 The following is an example of an "m=" line for a BFCP connection: 241 Offer (browser): 242 m=application 9 TCP/WSS/BFCP * 243 a=setup:active 244 a=connection:new 245 a=floorctrl:c-only 246 m=audio 55000 RTP/AVP 0 247 m=video 55002 RTP/AVP 31 249 In the above example, the client is intending to setup the TLS /TCP 250 connection and hence the port is set to a value of 9, which is the 251 discard port. 253 4.3. Generating the Answer 255 If the answerer accepts the offered WebSocket transport connection, 256 in the associated SDP answer, the answerer MUST assign an SDP "setup" 257 attribute with a value of either "active" or "passive", according to 258 the procedures in [RFC4145]. The answerer MUST NOT assign an SDP 259 "setup" attribute with a value of "holdconn". 261 If the answerer assigns an SDP "setup" attribute with a value of 262 "active", the answerer MUST initiate the WebSocket connection 263 handshake by acting as client on the negotiated media stream, towards 264 the IP address and port of the offerer using the procedures described 265 in [RFC6455]. The answer MUST have an "a=ws-uri" or "a=wss-uri" 266 attribute depending on whether the application is run of WS or WSS. 267 This attribute MUST follow the syntax defined in Section 3. For BFCP 268 application, the "proto" value in the "m=" line MUST be TCP/WSS/BFCP 269 if WebSocket is run on TLS, else it MUST be TCP/WS/BFCP. 271 The following example shows a case where the server responds with a 272 BFCP media stream over a WebSocket connection running TLS. It shows 273 an answer "m=" line for the BFCP connection. In this example since 274 WebSockets is running over TLS, the server answers back with "a=wss- 275 uri" attribute in SDP indicating the connection URI: 277 Answer (server): 278 m=application 50000 TCP/WSS/BFCP * 279 a=setup:passive 280 a=connection:new 281 a=wss-uri:wss://bfcp-ws.example.com?token=3170449312 282 a=floorctrl:s-only 283 a=confid:4321 284 a=userid:1234 285 a=floorid:1 m-stream:10 286 a=floorid:2 m-stream:11 287 m=audio 50002 RTP/AVP 0 288 a=label:10 289 m=video 50004 RTP/AVP 31 290 a=label:11 292 4.4. Offerer Processing of the Answer 294 When the offerer receives an SDP answer, if the offerer ends up being 295 active it MUST initiate the WebSocket connection handshake by sending 296 a GET message on the negotiated media stream, towards the IP address 297 and port of the answerer, as per the procedures described in 298 [RFC6455]. 300 4.5. Modifying the Session 302 Once an offer/answer exchange has been completed, either endpoint MAY 303 send a new offer in order to modify the session. The endpoints can 304 reuse the existing WebSocket connection if the ws-uri values and the 305 transport parameters indicated by each endpoint are unchanged. 306 Otherwise, following the rules for the initial offer/answer exchange, 307 the endpoints can negotiate and create a new WebSocket connection on 308 top of TLS/TCP or TCP. 310 5. Security Considerations 312 An attacker may attempt to add, modify, or remove 'a=ws-uri' or 313 'a=wss-uri' attribute from a session description. This could result 314 in an application behaving undesirably. Consequently, it is strongly 315 RECOMMENDED that integrity protection be applied to the SDP session 316 descriptions. For session descriptions carried in SIP [RFC3261], S/ 317 MIME is the natural choice to provide such end-to-end integrity 318 protection. 320 It is also RECOMMENDED that the application signaling traffic being 321 transported over a WebSocket communication session be protected by 322 using a secure WebSocket connection (using TLS [RFC5246] over TCP). 324 6. IANA Considerations 326 6.1. Registration of the 'ws-uri' SDP Media Attribute 328 NOTE to RFC Editor: Please replace "XXXX" with the number of this 329 RFC. 331 This document defines a new SDP media-level attribute "ws-uri" in 332 Section 3.2 and requests that IANA to register the following SDP att- 333 field under the Session Description Protocol (SDP) Parameters 334 registry as follows: 336 +---------------------+---------------------------------------------+ 337 | Attribute name: | ws-uri | 338 | Long-form attribute | Websocket Connection URI | 339 | name: | | 340 | Type of attribute: | media | 341 | Mux category: | NOT RECOMMENDED | 342 | Charset Dependent: | No | 343 | Purpose: | The 'ws-uri' attribute is intended to be | 344 | | used as a connection URI for opening the | 345 | | WebSocket connection. | 346 | Appropriate values: | A ws-URI as defined in [RFC6455] | 347 | Contact name: | Gonzalo Salgueiro | 348 | Contact e-mail: | gsalguei@cisco.com | 349 | Reference: | RFCXXXX | 350 +---------------------+---------------------------------------------+ 352 6.2. Registration of the 'wss-uri' SDP Media Attribute 354 NOTE to RFC Editor: Please replace "XXXX" with the number of this 355 RFC. 357 This document defines a new SDP media-level attribute "wss-uri" in 358 Section 3.3 and requests that IANA to register the following SDP att- 359 field under the Session Description Protocol (SDP) Parameters 360 registry as follows: 362 +---------------------+---------------------------------------------+ 363 | Attribute name: | wss-uri | 364 | Long-form attribute | Websocket Connection URI over Secure | 365 | name: | Transport | 366 | Type of attribute: | media | 367 | Mux category: | NOT RECOMMENDED | 368 | Charset Dependent: | No | 369 | Purpose: | The 'wss-uri' attribute is intended to be | 370 | | used as a connection URI for opening the | 371 | | WebSocket connection over a secure | 372 | | transport. | 373 | Appropriate values: | A wss-URI as defined in [RFC6455] | 374 | Contact name: | Gonzalo Salgueiro | 375 | Contact e-mail: | gsalguei@cisco.com | 376 | Reference: | RFCXXXX | 377 +---------------------+---------------------------------------------+ 379 7. Acknowledgements 381 Thanks to Christer Holmberg for raising the need for a BFCP- 382 independent SDP attribute for WebSocket Connection URI. 384 The authors wish to acknowledge Paul Kyzivat, Suhas Nandakumar, and 385 Christer Holmberg for their invaluable suggestions and review 386 comments. 388 8. References 390 8.1. Normative References 392 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 393 Requirement Levels", BCP 14, RFC 2119, 394 DOI 10.17487/RFC2119, March 1997, 395 . 397 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 398 the Session Description Protocol (SDP)", RFC 4145, 399 DOI 10.17487/RFC4145, September 2005, 400 . 402 [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", 403 RFC 6455, DOI 10.17487/RFC6455, December 2011, 404 . 406 8.2. Informative References 408 [I-D.ietf-bfcpbis-bfcp-websocket] 409 Pascual, V., Roman, A., Cazeaux, S., Salgueiro, G., R, R., 410 and S. Murillo, "The WebSocket Protocol as a Transport for 411 the Binary Floor Control Protocol (BFCP)", draft-ietf- 412 bfcpbis-bfcp-websocket-06 (work in progress), February 413 2016. 415 [I-D.ietf-bfcpbis-rfc4582bis] 416 Camarillo, G., Drage, K., Kristensen, T., Ott, J., and C. 417 Eckel, "The Binary Floor Control Protocol (BFCP)", draft- 418 ietf-bfcpbis-rfc4582bis-16 (work in progress), November 419 2015. 421 [I-D.ietf-mmusic-sdp-mux-attributes] 422 Nandakumar, S., "A Framework for SDP Attributes when 423 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12 424 (work in progress), January 2016. 426 [I-D.pd-dispatch-msrp-websocket] 427 Dunkley, P., Llewellyn, G., Pascual, V., Salgueiro, G., 428 and R. R, "The WebSocket Protocol as a Transport for the 429 Message Session Relay Protocol (MSRP)", draft-pd-dispatch- 430 msrp-websocket-10 (work in progress), February 2016. 432 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 433 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 434 Transfer Protocol -- HTTP/1.1", RFC 2616, 435 DOI 10.17487/RFC2616, June 1999, 436 . 438 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 439 DOI 10.17487/RFC2818, May 2000, 440 . 442 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 443 A., Peterson, J., Sparks, R., Handley, M., and E. 444 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 445 DOI 10.17487/RFC3261, June 2002, 446 . 448 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 449 with Session Description Protocol (SDP)", RFC 3264, 450 DOI 10.17487/RFC3264, June 2002, 451 . 453 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 454 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 455 July 2006, . 457 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 458 (TLS) Protocol Version 1.2", RFC 5246, 459 DOI 10.17487/RFC5246, August 2008, 460 . 462 [RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure 463 Sockets Layer (SSL) Protocol Version 3.0", RFC 6101, 464 DOI 10.17487/RFC6101, August 2011, 465 . 467 [RFC7118] Baz Castillo, I., Millan Villegas, J., and V. Pascual, 468 "The WebSocket Protocol as a Transport for the Session 469 Initiation Protocol (SIP)", RFC 7118, 470 DOI 10.17487/RFC7118, January 2014, 471 . 473 [RFC7395] Stout, L., Ed., Moffitt, J., and E. Cestari, "An 474 Extensible Messaging and Presence Protocol (XMPP) 475 Subprotocol for WebSocket", RFC 7395, 476 DOI 10.17487/RFC7395, October 2014, 477 . 479 [WS-API] W3C and I. Hickson, Ed., "The WebSocket API", May 2012. 481 Authors' Addresses 483 Ram Mohan Ravindranath 484 Cisco Systems, Inc. 485 Cessna Business Park, 486 Kadabeesanahalli Village, Varthur Hobli, 487 Sarjapur-Marathahalli Outer Ring Road 488 Bangalore, Karnataka 560103 489 India 491 Email: rmohanr@cisco.com 493 Gonzalo Salgueiro 494 Cisco Systems, Inc. 495 7200-12 Kit Creek Road 496 Research Triangle Park, NC 27709 497 US 499 Email: gsalguei@cisco.com