idnits 2.17.1 draft-ietf-tsvwg-rtcweb-qos-15.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 18, 2016) is 2960 days in the past. Is this intentional? 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-12) exists of draft-ietf-rtcweb-security-08 == Outdated reference: A later version (-17) exists of draft-ietf-rtcweb-transports-11 ** Downref: Normative reference to an Informational RFC: RFC 4594 ** Downref: Normative reference to an Informational RFC: RFC 7657 == Outdated reference: A later version (-09) exists of draft-ietf-rmcat-coupled-cc-00 -- Obsolete informational reference (is this intentional?): RFC 3662 (Obsoleted by RFC 8622) Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Jones 3 Internet-Draft S. Dhesikan 4 Intended status: Standards Track C. Jennings 5 Expires: September 19, 2016 Cisco Systems 6 D. Druta 7 AT&T 8 March 18, 2016 10 DSCP and other packet markings for WebRTC QoS 11 draft-ietf-tsvwg-rtcweb-qos-15 13 Abstract 15 Many networks, such as service provider and enterprise networks, can 16 provide different forwarding treatments for individual packets based 17 on Differentiated Services Code Point (DSCP) values on a per-hop 18 basis. This document provides the recommended DSCP values for web 19 browsers to use for various classes of WebRTC traffic. 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 September 19, 2016. 38 Copyright Notice 40 Copyright (c) 2016 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. Relation to Other Specifications . . . . . . . . . . . . . . 3 57 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5 60 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 61 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 62 8. Downward References . . . . . . . . . . . . . . . . . . . . . 7 63 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 64 10. Dedication . . . . . . . . . . . . . . . . . . . . . . . . . 8 65 11. Document History . . . . . . . . . . . . . . . . . . . . . . 8 66 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 12.1. Normative References . . . . . . . . . . . . . . . . . . 8 68 12.2. Informative References . . . . . . . . . . . . . . . . . 9 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 71 1. Introduction 73 Differentiated Services Code Point (DSCP) [RFC2474] packet marking 74 can help provide QoS in some environments. This specification 75 provides default packet marking for browsers that support WebRTC 76 applications, but does not change any advice or requirements in other 77 IETF RFCs. The contents of this specification are intended to be a 78 simple set of implementation recommendations based on the previous 79 RFCs. 81 There are many use cases where such marking does not help, but it 82 seldom makes things worse if packets are marked appropriately. There 83 are some environments where DSCP markings frequently help, though. 84 These include: 86 1. Private, wide-area networks. Network administrators have control 87 over remarking packets and treatment of packets. 89 2. Residential Networks. If the congested link is the broadband 90 uplink in a cable or DSL scenario, often residential routers/NAT 91 support preferential treatment based on DSCP. 93 3. Wireless Networks. If the congested link is a local wireless 94 network, marking may help. 96 DSCP values are in principle site specific, with each site selecting 97 its own code points for controlling per-hop-behavior to influence the 98 QoS for transport-layer flows. However in the WebRTC use cases, the 99 browsers need to set them to something when there is no site specific 100 information. In this document, "browsers" is used synonymously with 101 "Interactive User Agent" as defined in the HTML specification, 102 [W3C.REC-html5-20141028]. This document describes a subset of DSCP 103 code point values drawn from existing RFCs and common usage for use 104 with WebRTC applications. These code points are solely defaults. 106 This specification defines inputs that are provided by the WebRTC 107 application hosted in the browser that aid the browser in determining 108 how to set the various packet markings. The specification also 109 defines the mapping from abstract QoS policies (flow type, priority 110 level) to those packet markings. 112 2. Relation to Other Specifications 114 This document is a complement to [RFC7657], which describes the 115 interaction between DSCP and real-time communications. That RFC 116 covers the implications of using various DSCP values, particularly 117 focusing on Real-time Transport Protocol (RTP) [RFC3550] streams that 118 are multiplexed onto a single transport-layer flow. 120 There are a number of guidelines specified in [RFC7657] that apply to 121 marking traffic sent by WebRTC applications, as it is common for 122 multiple RTP streams to be multiplexed on the same transport-layer 123 flow. Generally, the RTP streams would be marked with a value as 124 appropriate from Table 1. A WebRTC application might also multiplex 125 data channel [I-D.ietf-rtcweb-data-channel] traffic over the same 126 5-tuple as RTP streams, which would also be marked as per that table. 127 The guidance in [RFC7657] says that all data channel traffic would be 128 marked with a single value that is typically different than the 129 value(s) used for RTP streams multiplexed with the data channel 130 traffic over the same 5-tuple, assuming RTP streams are marked with a 131 value other than default forwarding (DF). This is expanded upon 132 further in the next section. 134 This specification does not change or override the advice in any 135 other IETF RFCs about setting packet markings. Rather, it simply 136 selects a subset of DSCP values that is relevant in the WebRTC 137 context. 139 The DSCP value set by the endpoint is not trusted by the network. In 140 addition, the DSCP value may be remarked at any place in the network 141 for a variety of reasons to any other DSCP value, including default 142 forwarding (DF) value to provide basic best effort service. Even so, 143 there is benefit in marking traffic even if it only benefits the 144 first few hops. The implications are discussed in Secton 3.2 of 145 [RFC7657]. Further, a mitigation for such action is through an 146 authorization mechanism. Such an authorization mechanism is outside 147 the scope of this document. 149 3. Terminology 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in [RFC2119]. 155 4. Inputs 157 WebRTC applications send and receive two types of flows of 158 significance to this document: 160 o media flows which are RTP streams [I-D.ietf-rtcweb-rtp-usage] 162 o data flows which are data channels [I-D.ietf-rtcweb-data-channel] 164 Each of the RTP streams and distinct data channels consists of all of 165 the packets associated with an independent media entity, so an RTP 166 stream or distinct data channel is not always equivalent to a 167 transport-layer flow defined by a 5-tuple (source address, 168 destination address, source port, destination port, and protocol). 169 There may be multiple RTP streams and data channels multiplexed over 170 the same 5-tuple, with each having a different level of importance to 171 the application and, therefore, potentially marked using different 172 DSCP values than another RTP stream or data channel within the same 173 transport-layer flow. (Note that there are restrictions with respect 174 to marking different data channels carried within the same SCTP 175 association as outlined in Section 5.) 177 The following are the inputs provided by the WebRTC application to 178 the browser: 180 o Flow Type: The browser provides this input as it knows if the flow 181 is audio, interactive video with or without audio, non-interactive 182 video with or without audio, or data. 184 o Application Priority: Another input is the relative importance of 185 an RTP stream or data channel. Many applications have multiple 186 flows of the same Flow Type and often some flows are more 187 important than others. For example, in a video conference where 188 there are usually audio and video flows, the audio flow may be 189 more important than the video flow. JavaScript applications can 190 tell the browser whether a particular flow is high, medium, low or 191 very low importance to the application. 193 [I-D.ietf-rtcweb-transports] defines in more detail what an 194 individual flow is within the WebRTC context and priorities for media 195 and data flows. 197 5. DSCP Mappings 199 The DSCP values for each flow type of interest to WebRTC based on 200 application priority are shown in the following table. These values 201 are based on the framework and recommended values in [RFC4594]. A 202 web browser SHOULD use these values to mark the appropriate media 203 packets. More information on EF can be found in [RFC3246]. More 204 information on AF can be found in [RFC2597]. DF is default 205 forwarding which provides the basic best effort service [RFC2474]. 207 +------------------------+-------+------+-------------+-------------+ 208 | Flow Type | Very | Low | Medium | High | 209 | | Low | | | | 210 +------------------------+-------+------+-------------+-------------+ 211 | Audio | CS1 | DF | EF (46) | EF (46) | 212 | | (8) | (0) | | | 213 | | | | | | 214 | Interactive Video with | CS1 | DF | AF42, AF43 | AF41, AF42 | 215 | or without audio | (8) | (0) | (36, 38) | (34, 36) | 216 | | | | | | 217 | Non-Interactive Video | CS1 | DF | AF32, AF33 | AF31, AF32 | 218 | with or without audio | (8) | (0) | (28, 30) | (26, 28) | 219 | | | | | | 220 | Data | CS1 | DF | AF11 | AF21 | 221 | | (8) | (0) | | | 222 +------------------------+-------+------+-------------+-------------+ 224 Table 1: Recommended DSCP Values for WebRTC Applications 226 The application priority, indicated by the columns "very low", "low", 227 "Medium", and "high", signifies the relative importance of the flow 228 within the application. It is an input that the browser receives to 229 assist in selecting the DSCP value and adjusting the network 230 transport behavior. 232 The above table assumes that packets marked with CS1 are treated as 233 "less than best effort", such as the LE behavior described in 234 [RFC3662]. However, the treatment of CS1 is implementation 235 dependent. If an implementation treats CS1 as other than "less than 236 best effort", then the actual priority (or, more precisely, the per- 237 hop-behavior) of the packets may be changed from what is intended. 238 It is common for CS1 to be treated the same as DF, so applications 239 and browsers using CS1 cannot assume that CS1 will be treated 240 differently than DF [RFC7657]. However, it is also possible per 242 [RFC2474] for CS1 traffic to be given better treatment than DF, thus 243 caution should be exercised when electing to use CS1. This is one of 244 the cases where marking packets using these recommendations can make 245 things worse. 247 Implementers should also note that excess EF traffic is dropped. 248 This could mean that a packet marked as EF may not get through, 249 although the same packet marked with a different DSCP value would 250 have gotten through. This is not a flaw, but how excess EF traffic 251 is intended to be treated. 253 The browser SHOULD first select the flow type of the flow. Within 254 the flow type, the relative importance of the flow SHOULD be used to 255 select the appropriate DSCP value. 257 The combination of flow type and application priority provides 258 specificity and helps in selecting the right DSCP value for the flow. 259 All packets within a flow SHOULD have the same application priority. 260 In some cases, the selected application priority cell may have 261 multiple DSCP values, such as AF41 and AF42. These offer different 262 drop precedences. The different drop precedence values provides 263 additional granularity in classifying packets within a flow. For 264 example, in a video conference, the video flow may have medium 265 application priority. If so, either AF42 or AF43 may be selected. 266 If the I-frames in the stream are more important than the P-frames, 267 then the I-frames can be marked with AF42 and the P-frames marked 268 with AF43. (See Section 3 of [RFC6386] for a description of video 269 frame types.) 271 It is worth noting that the application priority is utilized by the 272 coupled congestion control mechanism for media flows per 273 [I-D.ietf-rmcat-coupled-cc] and the SCTP scheduler for data channel 274 traffic per [I-D.ietf-rtcweb-data-channel]. 276 For reasons discussed in Section 6 of [RFC7657], if multiple flows 277 are multiplexed using a reliable transport (e.g., TCP) then all of 278 the packets for all flows multiplexed over that transport-layer flow 279 MUST be marked using the same DSCP value. Likewise, all WebRTC data 280 channel packets transmitted over an SCTP association MUST be marked 281 using the same DSCP value, regardless of how many data channels 282 (streams) exist or what kind of traffic is carried over the various 283 SCTP streams. In the event that the browser wishes to change the 284 DSCP value in use for an SCTP association, it MUST reset the SCTP 285 congestion controller after changing values. Frequent changes in the 286 DSCP value used for an SCTP association are discouraged, though, as 287 this would defeat any attempts at effectively managing congestion. 288 It should also be noted that any change in DSCP value that results in 289 a reset of the congestion controller puts the SCTP association back 290 into slow start, which may have undesirable effects on application 291 performance. 293 For the data channel traffic multiplexed over an SCTP association, it 294 is RECOMMENDED that the DSCP value selected be the one associated 295 with the highest priority requested for all data channels multiplexed 296 over the SCTP association. Likewise, when multiplexing multiple 297 flows over a TCP connection, the DCSP value selected should be the 298 one associated with the highest priority requested for all 299 multiplexed flows. 301 If a packet enters a network that has no support for a flow type- 302 application priority combination specified in Table 1 (above), then 303 the network node at the edge will remark the DSCP value based on 304 policies. This could result in the flow not getting the network 305 treatment it expects based on the original DSCP value in the packet. 306 Subsequently, if the packet enters a network that supports a larger 307 number of these combinations, there may not be sufficient information 308 in the packet to restore the original markings. Mechanisms for 309 restoring such original DSCP is outside the scope of this document. 311 In summary, DSCP marking provides neither guarantees nor promised 312 levels of service. However, DSCP marking is expected to provide a 313 statistical improvement in real-time service as a whole. The service 314 provided to a packet is dependent upon the network design along the 315 path, as well as the network conditions at every hop. 317 6. Security Considerations 319 This specification does not add any additional security implications 320 beyond those addressed in the following DSCP-related specifications. 321 For security implications on use of DSCP, please refer to Section 7 322 of [RFC7657] and Section 6 of [RFC4594]. Please also see 323 [I-D.ietf-rtcweb-security] as an additional reference. 325 7. IANA Considerations 327 This specification does not require any actions from IANA. 329 8. Downward References 331 This specification contains a downwards reference to [RFC4594] and 332 [RFC7657]. However, the parts of the former RFC used by this 333 specification are sufficiently stable for this downward reference. 334 The guidance in the latter RFC is necessary to understand the 335 Diffserv technology used in this document and the motivation for the 336 recommended DSCP values and procedures. 338 9. Acknowledgements 340 Thanks to David Black, Magnus Westerland, Paolo Severini, Jim 341 Hasselbrook, Joe Marcus, Erik Nordmark, Michael Tuexen, and Brian 342 Carpenter for their invaluable input. 344 10. Dedication 346 This document is dedicated to the memory of James Polk, a long-time 347 friend and colleague. James made important contributions to this 348 specification, including serving initially as one of the primary 349 authors. The IETF global community mourns his loss and he will be 350 missed dearly. 352 11. Document History 354 Note to RFC Editor: Please remove this section. 356 This document was originally an individual submission in RTCWeb WG. 357 The RTCWeb working group selected it to be become a WG document. 358 Later the transport ADs requested that this be moved to the TSVWG WG 359 as that seemed to be a better match. 361 12. References 363 12.1. Normative References 365 [I-D.ietf-rtcweb-data-channel] 366 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data 367 Channels", draft-ietf-rtcweb-data-channel-13 (work in 368 progress), January 2015. 370 [I-D.ietf-rtcweb-rtp-usage] 371 Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time 372 Communication (WebRTC): Media Transport and Use of RTP", 373 draft-ietf-rtcweb-rtp-usage-26 (work in progress), March 374 2016. 376 [I-D.ietf-rtcweb-security] 377 Rescorla, E., "Security Considerations for WebRTC", draft- 378 ietf-rtcweb-security-08 (work in progress), February 2015. 380 [I-D.ietf-rtcweb-transports] 381 Alvestrand, H., "Transports for WebRTC", draft-ietf- 382 rtcweb-transports-11 (work in progress), January 2016. 384 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 385 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 386 RFC2119, March 1997, 387 . 389 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 390 Guidelines for DiffServ Service Classes", RFC 4594, DOI 391 10.17487/RFC4594, August 2006, 392 . 394 [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services 395 (Diffserv) and Real-Time Communication", RFC 7657, DOI 396 10.17487/RFC7657, November 2015, 397 . 399 12.2. Informative References 401 [I-D.ietf-rmcat-coupled-cc] 402 Islam, S., Welzl, M., and S. Gjessing, "Coupled congestion 403 control for RTP media", draft-ietf-rmcat-coupled-cc-00 404 (work in progress), September 2015. 406 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 407 "Definition of the Differentiated Services Field (DS 408 Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 409 10.17487/RFC2474, December 1998, 410 . 412 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 413 "Assured Forwarding PHB Group", RFC 2597, DOI 10.17487/ 414 RFC2597, June 1999, 415 . 417 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 418 J., Courtney, W., Davari, S., Firoiu, V., and D. 419 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 420 Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002, 421 . 423 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 424 Jacobson, "RTP: A Transport Protocol for Real-Time 425 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 426 July 2003, . 428 [RFC3662] Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort 429 Per-Domain Behavior (PDB) for Differentiated Services", 430 RFC 3662, DOI 10.17487/RFC3662, December 2003, 431 . 433 [RFC6386] Bankoski, J., Koleszar, J., Quillio, L., Salonen, J., 434 Wilkins, P., and Y. Xu, "VP8 Data Format and Decoding 435 Guide", RFC 6386, DOI 10.17487/RFC6386, November 2011, 436 . 438 [W3C.REC-html5-20141028] 439 Hickson, I., Berjon, R., Faulkner, S., Leithead, T., 440 Navara, E., O'Connor, E., and S. Pfeiffer, "HTML5", 441 World Wide Web Consortium Recommendation REC- 442 html5-20141028, October 2014, 443 . 445 Authors' Addresses 447 Paul E. Jones 448 Cisco Systems 450 Email: paulej@packetizer.com 452 Subha Dhesikan 453 Cisco Systems 455 Email: sdhesika@cisco.com 457 Cullen Jennings 458 Cisco Systems 460 Email: fluffy@cisco.com 462 Dan Druta 463 AT&T 465 Email: dd5826@att.com