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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group H. Alvestrand 3 Internet-Draft Google 4 Intended status: Standards Track March 31, 2014 5 Expires: October 2, 2014 7 Transports for RTCWEB 8 draft-ietf-rtcweb-transports-03 10 Abstract 12 This document describes the data transport protocols used by RTCWEB, 13 including the protocols used for interaction with intermediate boxes 14 such as firewalls, relays and NAT boxes. 16 Status of this Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on October 2, 2014. 33 Copyright Notice 35 Copyright (c) 2014 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. Requirements language . . . . . . . . . . . . . . . . . . . . 3 52 3. Transport and Middlebox specification . . . . . . . . . . . . 3 53 3.1. System-provided interfaces . . . . . . . . . . . . . . . . 3 54 3.2. Ability to use IPv4 and IPv6 . . . . . . . . . . . . . . . 4 55 3.3. Usage of temporary IPv6 addresses . . . . . . . . . . . . 4 56 3.4. Usage of Quality of Service - DSCP and Multiplexing . . . 4 57 3.5. Middle box related functions . . . . . . . . . . . . . . . 5 58 3.6. Transport protocols implemented . . . . . . . . . . . . . 6 59 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 60 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 61 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 62 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 63 7.1. Normative References . . . . . . . . . . . . . . . . . . . 7 64 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 65 Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 10 66 A.1. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 10 67 A.2. Changes from -01 to -02 . . . . . . . . . . . . . . . . . 10 68 A.3. Changes from -02 to -03 . . . . . . . . . . . . . . . . . 11 69 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 1. Introduction 73 The IETF RTCWEB effort, part of the WebRTC effort carried out in 74 cooperation between the IETF and the W3C, is aimed at specifying a 75 protocol suite that is useful for real time multimedia exchange 76 between browsers. 78 The overall effort is described in the RTCWEB overview document, 79 [I-D.ietf-rtcweb-overview]. This document focuses on the data 80 transport protocols that are used by conforming implementations. 82 This protocol suite is designed for WebRTC, and intends to satisfy 83 the security considerations described in the WebRTC security 84 documents, [I-D.ietf-rtcweb-security] and 85 [I-D.ietf-rtcweb-security-arch]. 87 2. Requirements language 89 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 90 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 91 document are to be interpreted as described in RFC 2119 [RFC2119]. 93 3. Transport and Middlebox specification 95 3.1. System-provided interfaces 97 The protocol specifications used here assume that the following 98 protocols are available to the implementations of the RTCWEB 99 protocols: 101 o UDP. This is the protocol assumed by most protocol elements 102 described. 104 o TCP. This is used for HTTP/WebSockets, as well as for TURN/SSL 105 and ICE-TCP. 107 For both protocols, IPv4 and IPv6 support is assumed. 109 For UDP, this specification assumes the ability to set the DSCP code 110 point of the sockets opened on a per-packet basis, in order to 111 achieve the prioritizations described in 112 [I-D.dhesikan-tsvwg-rtcweb-qos] (see Section 3.4) when multiple media 113 types are multiplexed. It does not assume that the DSCP codepoints 114 will be honored, and does assume that they may be zeroed or changed, 115 since this is a local configuration issue. 117 Platforms that do not give access to these interfaces will not be 118 able to support a conforming RTCWEB implementation. 120 This specification does not assume that the implementation will have 121 access to ICMP or raw IP. 123 3.2. Ability to use IPv4 and IPv6 125 Web applications running on top of the RTCWEB implementation MUST be 126 able to utilize both IPv4 and IPv6 where available - that is, when 127 two peers have only IPv4 connectivty to each other, or they have only 128 IPv6 connectivity to each other, applications running on top of the 129 RTCWEB implementation MUST be able to communicate. 131 When TURN is used, and the TURN server has IPv4 or IPv6 connectivity 132 to the peer or its TURN server, candidates of the appropriate types 133 MUST be supported. The "Happy Eyeballs" specification for ICE 134 [I-D.reddy-mmusic-ice-happy-eyeballs] SHOULD be supported. 136 3.3. Usage of temporary IPv6 addresses 138 The IPv6 default address selection specification [RFC6724] specifies 139 that temporary addresses [RFC4941] are to be preferred over permanent 140 addresses. This is a change from the rules specified by [RFC3484]. 141 For applications that select a single address, this is usually done 142 by the IPV6_PREFER_SRC_TMP specified in [RFC5014]. However, this 143 rule is not completely obvious in the ICE scope. This is therefore 144 clarified as follows: 146 When a client gathers all IPv6 addresses on a host, and both 147 temporary addresses and permanent addresses of the same scope are 148 present, the client SHOULD discard the permanent addresses before 149 forming pairs. This is consistent with the default policy described 150 in [RFC6724]. 152 3.4. Usage of Quality of Service - DSCP and Multiplexing 154 WebRTC implementations SHOULD attempt to set QoS on the packets sent, 155 according to the guidelines in [I-D.dhesikan-tsvwg-rtcweb-qos]. It 156 is appropriate to depart from this recommendation when running on 157 platforms where QoS marking is not implemented. 159 There exist a number of schemes for achieving quality of service that 160 do not depend solely on DSCP code points. Some of these schemes 161 depend on classifying the traffic into flows based on 5-tuple (source 162 address, source port, protocol, destination address, destination 163 port) or 6-tuple (same as above + DSCP code point). Under differing 164 conditions, it may therefore make sense for a sending application to 165 choose any of the configurations: 167 o Each media stream carried on its own 5-tuple 169 o Media streams grouped by media type into 5-tuples (such as 170 carrying all audio on one 5-tuple) 172 o All media sent over a single 5-tuple, with or without 173 differentiation into 6-tuples based on DSCP code points 175 In each of the configurations mentioned, data channels may be carried 176 in its own 5-tuple, or multiplexed together with one of the media 177 flows. 179 More complex configurations, such as sending a high priority video 180 stream on one 5-tuple and sending all other video streams multiplexed 181 together over another 5-tuple, can also be envisioned. 183 A sending implementation MUST be able to multiplex all media and data 184 on a single 5-tuple (fully bundled), MUST be able to send each media 185 stream and data on their own 5-tuple (fully unbundled), and MAY 186 choose to support other configurations. 188 NOTE IN DRAFT: is there a need to place the "group by media type, 189 with data multiplexed on the video" as a MUST or SHOULD 190 configuration? 192 A receiving implementation MUST be able to receive media and data in 193 all these configurations. 195 3.5. Middle box related functions 197 The primary mechanism to deal with middle boxes is ICE, which is an 198 appropriate way to deal with NAT boxes and firewalls that accept 199 traffic from the inside, but only from the outside if it's in 200 response to inside traffic (simple stateful firewalls). 202 ICE [RFC5245] MUST be supported. The implementation MUST be a full 203 ICE implementation, not ICE-Lite. 205 In order to deal with situations where both parties are behind NATs 206 which perform endpoint-dependent mapping (as defined in [RFC5128] 207 section 2.4), TURN [RFC5766] MUST be supported. 209 Configuration of STUN and TURN servers, both from browser 210 configuration and from an applicaiton, MUST be supported. 212 In order to deal with firewalls that block all UDP traffic, TURN 213 using TCP between the client and the server MUST be supported, and 214 TURN using TLS over TCP between the client and the server MUST be 215 supported. See [RFC5766] section 2.1 for details. 217 In order to deal with situations where one party is on an IPv4 218 network and the other party is on an IPv6 network, TURN extensions 219 for IPv6 [RFC6156] MUST be supported. 221 TURN TCP candidates [RFC6062] MAY be supported. 223 However, such candidates are not seen as providing any significant 224 benefit. First, use of TURN TCP would only be relevant in cases 225 which both peers are required to use TCP to establish a 226 PeerConnection. Secondly, that use case is anyway supported by both 227 sides establishing UDP relay candidates using TURN over TCP to 228 connect to the relay server. Thirdly, using TCP only between the 229 endpoint and its relay may result in less issues with TCP in regards 230 to real-time constraints, e.g. due to head of line blocking. 232 ICE-TCP candidates [RFC6544] MAY be supported; this may allow 233 applications to communicate to peers with public IP addresses across 234 UDP-blocking firewalls without using a TURN server. 236 If TCP connections are used, RTP framing according to [RFC4571] MUST 237 be used, both for the RTP packets and for the DTLS packets used to 238 carry data channels. 240 The ALTERNATE-SERVER mechanism specified in [RFC5389] (STUN) section 241 11 (300 Try Alternate) MUST be supported. 243 Further discussion of the interaction of RTCWEB with firewalls is 244 contained in [I-D.hutton-rtcweb-nat-firewall-considerations]. This 245 document makes no requirements on interacting with HTTP proxies or 246 HTTP proxy configuration methods. 248 NOTE IN DRAFT: This may be added. 250 3.6. Transport protocols implemented 252 For transport of media, secure RTP is used. The details of the 253 profile of RTP used are described in "RTP Usage" 254 [I-D.ietf-rtcweb-rtp-usage]. 256 For data transport over the RTCWEB data channel 257 [I-D.ietf-rtcweb-data-channel], RTCWEB implementations MUST support 258 SCTP over DTLS over ICE. This encapsulation is specified in 259 [I-D.ietf-tsvwg-sctp-dtls-encaps]. Negotiation of this transport in 260 SDP is defined in [I-D.ietf-mmusic-sctp-sdp]. The SCTP extension for 261 NDATA, [I-D.ietf-tsvwg-sctp-ndata], MUST be supported. 263 The setup protocol for RTCWEB data channels is described in 264 [I-D.jesup-rtcweb-data-protocol]. 266 RTCWEB implementations MUST support multiplexing of DTLS and RTP over 267 the same port pair, as described in the DTLS_SRTP specification 268 [RFC5764], section 5.1.2. All application layer protocol payloads 269 over this DTLS connection are SCTP packets. 271 4. IANA Considerations 273 This document makes no request of IANA. 275 Note to RFC Editor: this section may be removed on publication as an 276 RFC. 278 5. Security Considerations 280 Security considerations are enumerated in [I-D.ietf-rtcweb-security]. 282 6. Acknowledgements 284 This document is based on earlier versions embedded in 285 [I-D.ietf-rtcweb-overview], which were the results of contributions 286 from many RTCWEB WG members. 288 Special thanks for reviews of earlier versions of this draft go to 289 Magnus Westerlund, Markus Isomaki and Dan Wing; the contributions 290 from Andrew Hutton also deserve special mention. 292 7. References 294 7.1. Normative References 296 [I-D.dhesikan-tsvwg-rtcweb-qos] 297 Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and 298 other packet markings for RTCWeb QoS", 299 draft-dhesikan-tsvwg-rtcweb-qos-06 (work in progress), 300 March 2014. 302 [I-D.ietf-mmusic-sctp-sdp] 303 Loreto, S. and G. Camarillo, "Stream Control Transmission 304 Protocol (SCTP)-Based Media Transport in the Session 305 Description Protocol (SDP)", draft-ietf-mmusic-sctp-sdp-06 306 (work in progress), February 2014. 308 [I-D.ietf-rtcweb-data-channel] 309 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data 310 Channels", draft-ietf-rtcweb-data-channel-07 (work in 311 progress), February 2014. 313 [I-D.ietf-rtcweb-rtp-usage] 314 Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time 315 Communication (WebRTC): Media Transport and Use of RTP", 316 draft-ietf-rtcweb-rtp-usage-12 (work in progress), 317 February 2014. 319 [I-D.ietf-rtcweb-security] 320 Rescorla, E., "Security Considerations for WebRTC", 321 draft-ietf-rtcweb-security-06 (work in progress), 322 January 2014. 324 [I-D.ietf-rtcweb-security-arch] 325 Rescorla, E., "WebRTC Security Architecture", 326 draft-ietf-rtcweb-security-arch-09 (work in progress), 327 February 2014. 329 [I-D.ietf-tsvwg-sctp-dtls-encaps] 330 Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS 331 Encapsulation of SCTP Packets", 332 draft-ietf-tsvwg-sctp-dtls-encaps-03 (work in progress), 333 February 2014. 335 [I-D.ietf-tsvwg-sctp-ndata] 336 Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "A 337 New Data Chunk for Stream Control Transmission Protocol", 338 draft-ietf-tsvwg-sctp-ndata-00 (work in progress), 339 February 2014. 341 [I-D.reddy-mmusic-ice-happy-eyeballs] 342 Reddy, T., Patil, P., and P. Martinsen, "Happy Eyeballs 343 Extension for ICE", 344 draft-reddy-mmusic-ice-happy-eyeballs-06 (work in 345 progress), February 2014. 347 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 348 Requirement Levels", BCP 14, RFC 2119, March 1997. 350 [RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP) 351 and RTP Control Protocol (RTCP) Packets over Connection- 352 Oriented Transport", RFC 4571, July 2006. 354 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 355 Extensions for Stateless Address Autoconfiguration in 356 IPv6", RFC 4941, September 2007. 358 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 359 (ICE): A Protocol for Network Address Translator (NAT) 360 Traversal for Offer/Answer Protocols", RFC 5245, 361 April 2010. 363 [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 364 "Session Traversal Utilities for NAT (STUN)", RFC 5389, 365 October 2008. 367 [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer 368 Security (DTLS) Extension to Establish Keys for the Secure 369 Real-time Transport Protocol (SRTP)", RFC 5764, May 2010. 371 [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using 372 Relays around NAT (TURN): Relay Extensions to Session 373 Traversal Utilities for NAT (STUN)", RFC 5766, April 2010. 375 [RFC6062] Perreault, S. and J. Rosenberg, "Traversal Using Relays 376 around NAT (TURN) Extensions for TCP Allocations", 377 RFC 6062, November 2010. 379 [RFC6156] Camarillo, G., Novo, O., and S. Perreault, "Traversal 380 Using Relays around NAT (TURN) Extension for IPv6", 381 RFC 6156, April 2011. 383 [RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach, 384 "TCP Candidates with Interactive Connectivity 385 Establishment (ICE)", RFC 6544, March 2012. 387 [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, 388 "Default Address Selection for Internet Protocol Version 6 389 (IPv6)", RFC 6724, September 2012. 391 7.2. Informative References 393 [I-D.hutton-rtcweb-nat-firewall-considerations] 394 Stach, T., Hutton, A., and J. Uberti, "RTCWEB 395 Considerations for NATs, Firewalls and HTTP proxies", 396 draft-hutton-rtcweb-nat-firewall-considerations-03 (work 397 in progress), January 2014. 399 [I-D.ietf-rtcweb-overview] 400 Alvestrand, H., "Overview: Real Time Protocols for Brower- 401 based Applications", draft-ietf-rtcweb-overview-09 (work 402 in progress), February 2014. 404 [I-D.jesup-rtcweb-data-protocol] 405 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel 406 Protocol", draft-jesup-rtcweb-data-protocol-04 (work in 407 progress), February 2013. 409 [RFC3484] Draves, R., "Default Address Selection for Internet 410 Protocol version 6 (IPv6)", RFC 3484, February 2003. 412 [RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 413 Socket API for Source Address Selection", RFC 5014, 414 September 2007. 416 [RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-to- 417 Peer (P2P) Communication across Network Address 418 Translators (NATs)", RFC 5128, March 2008. 420 Appendix A. Change log 422 A.1. Changes from -00 to -01 424 o Clarified DSCP requirements, with reference to -qos- 426 o Clarified "symmetric NAT" -> "NATs which perform endpoint- 427 dependent mapping" 429 o Made support of TURN over TCP mandatory 431 o Made support of TURN over TLS a MAY, and added open question 433 o Added an informative reference to -firewalls- 435 o Called out that we don't make requirements on HTTP proxy 436 interaction (yet 438 A.2. Changes from -01 to -02 440 o Required support for 300 Alternate Server from STUN. 442 o Separated the ICE-TCP candidate requirement from the TURN-TCP 443 requirement. 445 o Added new sections on using QoS functions, and on multiplexing 446 considerations. 448 o Removed all mention of RTP profiles. Those are the business of 449 the RTP usage draft, not this one. 451 o Required support for TURN IPv6 extensions. 453 o Removed reference to the TURN URI scheme, as it was unnecessary. 455 o Made an explicit statement that multiplexing (or not) is an 456 application matter. 458 . 460 A.3. Changes from -02 to -03 462 o Added required support for draft-ietf-tsvwg-sctp-ndata 464 o Removed discussion of multiplexing, since this is present in rtp- 465 usage. 467 o Added RFC 4571 reference for framing RTP packets over TCP. 469 o Downgraded TURN TCP candidates from SHOULD to MAY, and added more 470 language discussing TCP usage. 472 o Added language on IPv6 temporary addresses. 474 o Added language describing multiplexing choices. 476 o Added a separate section detailing what it means when we say that 477 an RTCWEB implementation MUST support both IPv4 and IPv6. 479 Author's Address 481 Harald Alvestrand 482 Google 484 Email: harald@alvestrand.no