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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: January 21, 2017 July 20, 2016 7 Session Description Protocol (SDP) WebSocket Connection URI Attribute 8 draft-ietf-bfcpbis-sdp-ws-uri-05 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 January 21, 2017. 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 4.6. Offerless INVITE Scenarios . . . . . . . . . . . . . . . 7 65 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 67 6.1. Registration of the 'ws-uri' SDP Media Attribute . . . . 8 68 6.2. Registration of the 'wss-uri' SDP Media Attribute . . . . 8 69 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 70 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 71 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 72 8.2. Informative References . . . . . . . . . . . . . . . . . 10 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 75 1. Introduction 77 The WebSocket protocol [RFC6455] enables bidirectional message 78 exchange between clients and servers on top of a persistent TCP 79 connection (optionally secured with Transport Layer Security (TLS) 80 [RFC5246]). The initial protocol handshake makes use of Hypertext 81 Transfer Protocol (HTTP) [RFC7230] semantics, allowing the WebSocket 82 protocol to reuse existing HTTP infrastructure. 84 Modern web browsers include a WebSocket client stack compliant with 85 the WebSocket API [WS-API] as specified by the W3C. It is expected 86 that other client applications (e.g., those running on personal 87 computers, mobile devices, etc.) will also make a WebSocket client 88 stack available. Several specifications have been written that 89 define how different applications can use a WebSocket subprotocol as 90 a reliable transport mechanism. 92 For example, [RFC7118] defines WebSocket subprotocol as a reliable 93 transport mechanism between Session Initiation Protocol 94 (SIP)[RFC3261] entities to enable use of SIP in web-oriented 95 deployments. Additionally, [I-D.pd-dispatch-msrp-websocket] defines 96 a new WebSocket sub-protocol as a reliable transport mechanism 97 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", "NOT RECOMMENDED", "MAY", and 123 "OPTIONAL" in this document are to be interpreted as described in 124 [RFC2119]. 126 3. SDP Considerations 128 3.1. General 130 Applications that use the SDP Offer/Answer mechanism [RFC3264] for 131 negotiating media and also use WebSocket as a transport protocol MAY 132 indicate the connection URI for the WebSocket Client via a new SDP a= 133 media-level attribute defined in Section 3.2. 135 Applications that use SDP for negotiation and also use secure 136 WebSocket as a transport protocol TLS MAY indicate the connection URI 137 for the WebSocket Client via a new SDP a= media-level attribute 138 defined in Section 3.3. 140 3.2. ws-uri SDP Attribute 142 This section defines a new SDP media-level attribute, 'ws-uri' which 143 can appear in any of the media sections. 145 Example: 147 a=ws-uri:ws://example.com/chat 149 Where "ws://example.com/chat" is the ws-URI defined in Section 3 of 150 [RFC6455]. 152 When the 'ws-uri' attribute is present in the media section of the 153 SDP, the IP address in 'c= ' line SHALL be ignored and the full URI 154 SHALL be used instead to open the WebSocket connection. The port 155 provided in the 'm= ' line SHALL be ignored too, as the 'a=ws-uri' 156 SHALL provide port number when needed. 158 3.3. wss-uri SDP Attribute 160 This section defines a new SDP media-level attribute, 'wss-uri' which 161 can appear in any of the media sections. 163 Example: 165 a=wss-uri:wss://example.com/chat 167 Here "wss://example.com/chat" is the wss-URI defined in Section 3 of 168 [RFC6455]. 170 When the 'wss-uri' attribute is present in the media section of the 171 SDP, the IP address in 'c= ' line SHALL be ignored and the full URI 172 SHALL be used instead to open the secure WebSocket connection. The 173 port provided in the 'm= ' line SHALL be ignored too, as the 'a=wss- 174 uri' SHALL provide port number when needed. 176 3.4. ws-uri and wss-uri Multiplexing Considerations 178 Multiplexing characteristics of SDP attributes are described in 179 [I-D.ietf-mmusic-sdp-mux-attributes]. Various SDP attribute 180 multiplexing categories are introduced there. 182 o The multiplexing category of the "a=ws-uri:" attribute is CAUTION. 184 o The multiplexing category of the "a=wss-uri:" attribute is 185 CAUTION. 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 CAUTION for 198 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 secure WebSocket in the "proto" field of 212 the "m=" line. Furthermore, the server side, which could be either 213 the offerer or answerer, MUST add an "a=ws-uri" or "a=wss-uri" 214 attribute in the media section depending on whether it wishes to use 215 WebSocket or secure WebSocket. This new attribute MUST follow the 216 syntax defined in Section 3. The procedures in this section apply to 217 an "m=" line associated with any media stream that uses WebSocket or 218 secure WebSocket 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 uses WebSocket or 267 secureWebSocket. This attribute MUST follow the syntax defined in 268 Section 3. For BFCP application, the "proto" value in the "m=" line 269 MUST be TCP/WSS/BFCP if WebSocket is run on TLS, else it MUST be 270 TCP/WS/BFCP. 272 The following example shows a case where the server responds with a 273 BFCP media stream over a WebSocket connection running TLS. It shows 274 an answer "m=" line for the BFCP connection. In this example since 275 WebSockets is running over TLS, the server answers back with "a=wss- 276 uri" attribute in the media section of SDP indicating the connection 277 URI: 279 Answer (server): 280 m=application 50000 TCP/WSS/BFCP * 281 a=setup:passive 282 a=connection:new 283 a=wss-uri:wss://bfcp-ws.example.com?token=3170449312 284 a=floorctrl:s-only 285 a=confid:4321 286 a=userid:1234 287 a=floorid:1 m-stream:10 288 a=floorid:2 m-stream:11 289 m=audio 50002 RTP/AVP 0 290 a=label:10 291 m=video 50004 RTP/AVP 31 292 a=label:11 294 4.4. Offerer Processing of the Answer 296 When the offerer receives an SDP answer, if the offerer ends up being 297 active it MUST initiate the WebSocket connection handshake by sending 298 a GET message on the negotiated media stream, towards the IP address 299 and port of the answerer, as per the procedures described in 300 [RFC6455]. 302 4.5. Modifying the Session 304 Once an offer/answer exchange has been completed, either endpoint MAY 305 send a new offer in order to modify the session. The endpoints can 306 reuse the existing WebSocket connection by adding 307 "a=connection:existing" attribute in the media section of SDP 308 following the rules mentioned in [RFC4145] if the ws-uri values and 309 the transport parameters indicated by each endpoint are unchanged. 310 Otherwise, following the rules for the initial offer/answer exchange, 311 the endpoints can negotiate and create a new WebSocket connection on 312 top of TLS/TCP or TCP. 314 4.6. Offerless INVITE Scenarios 316 In some scenarios an endpoint (e.g., a browser) originating the call 317 (UAC) can send an offerless INVITE to the server. The server will 318 generate an offer in response to the INVITE. In such cases the 319 server MUST send an offer with setup attribute as "passive" so as to 320 accept incoming connection and MUST include "a=wss-uri" or "a=ws-uri" 321 attribute in the media section depending on whether the server wishes 322 to use WebSocket or secure WebSocket. The SDP offer sent by the 323 server will look like the example in Section 4.3. 325 5. Security Considerations 327 An attacker may attempt to add, modify, or remove 'a=ws-uri' or 328 'a=wss-uri' attribute from a session description. This could result 329 in an application behaving undesirably. Consequently, it is strongly 330 RECOMMENDED that integrity protection be applied to the SDP session 331 descriptions. For session descriptions carried in SIP [RFC3261], S/ 332 MIME is the natural choice to provide such end-to-end integrity 333 protection. 335 It is also RECOMMENDED that the application signaling traffic being 336 transported over a WebSocket communication session be protected by 337 using a secure WebSocket connection (using TLS [RFC5246] over TCP). 339 6. IANA Considerations 341 6.1. Registration of the 'ws-uri' SDP Media Attribute 343 NOTE to RFC Editor: Please replace "XXXX" with the number of this 344 RFC. 346 This document defines a new SDP media-level attribute "ws-uri" in 347 Section 3.2 and requests that IANA to register the following SDP att- 348 field under the Session Description Protocol (SDP) Parameters 349 registry as follows: 351 +---------------------+---------------------------------------------+ 352 | Attribute name: | ws-uri | 353 | Long-form attribute | Websocket Connection URI | 354 | name: | | 355 | Type of attribute: | media | 356 | Mux category: | CAUTION | 357 | Charset Dependent: | No | 358 | Purpose: | The 'ws-uri' attribute is intended to be | 359 | | used as a connection URI for opening the | 360 | | WebSocket connection. | 361 | Appropriate values: | A ws-URI as defined in [RFC6455] | 362 | Contact name: | Gonzalo Salgueiro | 363 | Contact e-mail: | gsalguei@cisco.com | 364 | Reference: | RFCXXXX | 365 +---------------------+---------------------------------------------+ 367 6.2. Registration of the 'wss-uri' SDP Media Attribute 369 NOTE to RFC Editor: Please replace "XXXX" with the number of this 370 RFC. 372 This document defines a new SDP media-level attribute "wss-uri" in 373 Section 3.3 and requests that IANA to register the following SDP att- 374 field under the Session Description Protocol (SDP) Parameters 375 registry as follows: 377 +---------------------+---------------------------------------------+ 378 | Attribute name: | wss-uri | 379 | Long-form attribute | Websocket Connection URI over Secure | 380 | name: | Transport | 381 | Type of attribute: | media | 382 | Mux category: | CAUTION | 383 | Charset Dependent: | No | 384 | Purpose: | The 'wss-uri' attribute is intended to be | 385 | | used as a connection URI for opening the | 386 | | WebSocket connection over a secure | 387 | | transport. | 388 | Appropriate values: | A wss-URI as defined in [RFC6455] | 389 | Contact name: | Gonzalo Salgueiro | 390 | Contact e-mail: | gsalguei@cisco.com | 391 | Reference: | RFCXXXX | 392 +---------------------+---------------------------------------------+ 394 7. Acknowledgements 396 Thanks to Christer Holmberg for raising the need for a BFCP- 397 independent SDP attribute for WebSocket Connection URI. 399 The authors wish to acknowledge Paul Kyzivat, Suhas Nandakumar, 400 Christer Holmberg and Charles Eckel for their invaluable suggestions 401 and review comments. 403 8. References 405 8.1. Normative References 407 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 408 Requirement Levels", BCP 14, RFC 2119, 409 DOI 10.17487/RFC2119, March 1997, 410 . 412 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 413 the Session Description Protocol (SDP)", RFC 4145, 414 DOI 10.17487/RFC4145, September 2005, 415 . 417 [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", 418 RFC 6455, DOI 10.17487/RFC6455, December 2011, 419 . 421 8.2. Informative References 423 [I-D.ietf-bfcpbis-bfcp-websocket] 424 Pascual, V., Roman, A., Cazeaux, S., Salgueiro, G., R, R., 425 and S. Murillo, "The WebSocket Protocol as a Transport for 426 the Binary Floor Control Protocol (BFCP)", draft-ietf- 427 bfcpbis-bfcp-websocket-10 (work in progress), June 2016. 429 [I-D.ietf-bfcpbis-rfc4582bis] 430 Camarillo, G., Drage, K., Kristensen, T., Ott, J., and C. 431 Eckel, "The Binary Floor Control Protocol (BFCP)", draft- 432 ietf-bfcpbis-rfc4582bis-16 (work in progress), November 433 2015. 435 [I-D.ietf-mmusic-sdp-mux-attributes] 436 Nandakumar, S., "A Framework for SDP Attributes when 437 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-13 438 (work in progress), June 2016. 440 [I-D.pd-dispatch-msrp-websocket] 441 Dunkley, P., Llewellyn, G., Pascual, V., Salgueiro, G., 442 and R. R, "The WebSocket Protocol as a Transport for the 443 Message Session Relay Protocol (MSRP)", draft-pd-dispatch- 444 msrp-websocket-12 (work in progress), May 2016. 446 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 447 DOI 10.17487/RFC2818, May 2000, 448 . 450 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 451 A., Peterson, J., Sparks, R., Handley, M., and E. 452 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 453 DOI 10.17487/RFC3261, June 2002, 454 . 456 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 457 with Session Description Protocol (SDP)", RFC 3264, 458 DOI 10.17487/RFC3264, June 2002, 459 . 461 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 462 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 463 July 2006, . 465 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 466 (TLS) Protocol Version 1.2", RFC 5246, 467 DOI 10.17487/RFC5246, August 2008, 468 . 470 [RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure 471 Sockets Layer (SSL) Protocol Version 3.0", RFC 6101, 472 DOI 10.17487/RFC6101, August 2011, 473 . 475 [RFC7118] Baz Castillo, I., Millan Villegas, J., and V. Pascual, 476 "The WebSocket Protocol as a Transport for the Session 477 Initiation Protocol (SIP)", RFC 7118, 478 DOI 10.17487/RFC7118, January 2014, 479 . 481 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 482 Protocol (HTTP/1.1): Message Syntax and Routing", 483 RFC 7230, DOI 10.17487/RFC7230, June 2014, 484 . 486 [RFC7395] Stout, L., Ed., Moffitt, J., and E. Cestari, "An 487 Extensible Messaging and Presence Protocol (XMPP) 488 Subprotocol for WebSocket", RFC 7395, 489 DOI 10.17487/RFC7395, October 2014, 490 . 492 [WS-API] W3C and I. Hickson, Ed., "The WebSocket API", May 2012. 494 Authors' Addresses 496 Ram Mohan Ravindranath 497 Cisco Systems, Inc. 498 Cessna Business Park, 499 Kadabeesanahalli Village, Varthur Hobli, 500 Sarjapur-Marathahalli Outer Ring Road 501 Bangalore, Karnataka 560103 502 India 504 Email: rmohanr@cisco.com 506 Gonzalo Salgueiro 507 Cisco Systems, Inc. 508 7200-12 Kit Creek Road 509 Research Triangle Park, NC 27709 510 US 512 Email: gsalguei@cisco.com