idnits 2.17.1 draft-ietf-tsvwg-rtcweb-qos-04.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 seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords -- however, there's a paragraph with a matching beginning. Boilerplate error? (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (July 06, 2015) is 3218 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) ** Downref: Normative reference to an Informational draft: draft-ietf-dart-dscp-rtp (ref. 'I-D.ietf-dart-dscp-rtp') == Outdated reference: A later version (-12) exists of draft-ietf-rtcweb-security-07 == Outdated reference: A later version (-17) exists of draft-ietf-rtcweb-transports-08 ** Downref: Normative reference to an Informational RFC: RFC 4594 Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Dhesikan 3 Internet-Draft C. Jennings 4 Intended status: Standards Track Cisco Systems 5 Expires: January 07, 2016 D. Druta, Ed. 6 AT&T 7 P. Jones 8 J. Polk 9 Cisco Systems 10 July 06, 2015 12 DSCP and other packet markings for RTCWeb QoS 13 draft-ietf-tsvwg-rtcweb-qos-04 15 Abstract 17 Many networks, such as service provider and enterprise networks, can 18 provide treatment for individual packets based on Differentiated 19 Services Code Point (DSCP) values on a per-hop basis. This document 20 provides the recommended DSCP values for browsers to use for various 21 classes of traffic. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on January 07, 2016. 40 Copyright Notice 42 Copyright (c) 2015 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Relation to Other Standards . . . . . . . . . . . . . . . . . 3 59 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 61 5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 63 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 64 8. Downward References . . . . . . . . . . . . . . . . . . . . . 7 65 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 66 10. Document History . . . . . . . . . . . . . . . . . . . . . . 7 67 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 68 11.1. Normative References . . . . . . . . . . . . . . . . . . 7 69 11.2. Informative References . . . . . . . . . . . . . . . . . 8 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 72 1. Introduction 74 Differentiated Services Code Points (DSCP) [RFC2474] style packet 75 marking can help provide QoS in some environments. There are many 76 use cases where such marking does not help, but it seldom makes 77 things worse if packets are marked appropriately. In other words, if 78 too many packets, say all audio or all audio and video, are marked 79 for a given network condition then it can prevent desirable results. 80 Either too much other traffic will be starved, or there is not enough 81 capacity for the preferentially marked packets (i.e., audio and/or 82 video). 84 This specification proposes how WebRTC applications can mark packets. 85 This specification does not contradict or redefine any advice from 86 previous IETF RFCs, but merely provides a simple set of 87 recommendations for implementers based on the previous RFCs 89 There are some environments where DSCP markings frequently help. 90 These include: 92 1. Private, wide-area networks. 94 2. Residential Networks. If the congested link is the broadband 95 uplink in a cable or DSL scenario, often residential routers/NAT 96 support preferential treatment based on DSCP. 98 3. Wireless Networks. If the congested link is a local wireless 99 network, marking may help. 101 Traditionally DSCP values have been thought of as being site 102 specific, with each site selecting its own code points for 103 controlling per-hop-behavior to influence the QoS for transport 104 flows. However in the RTCWeb use cases, the browsers need to set 105 them to something when there is no site specific information. In 106 this document, "browsers" is used synonymously with "Interactive User 107 Agent" as defined in the HTML specification, 108 [W3C.REC-html5-20141028]. This document describes a subset of DSCP 109 code point values drawn from existing RFCs and common usage for use 110 with WebRTC applications. These code points are solely defaults. 112 This specification defines some inputs that the browser in a WebRTC 113 application can consider to aid in determining how to set the various 114 packet markings and defines the mapping from abstract QoS policies 115 (data type, priority level) to those packet markings. 117 2. Relation to Other Standards 119 This document exists as a complement to [I-D.ietf-dart-dscp-rtp], 120 which describes the interaction between DSCP and real-time 121 communications. It covers the implications of using various DSCP 122 values, particularly focusing on Real-time Transport Protocol (RTP) 123 [RFC3550] streams that are multiplexed onto a single transport-layer 124 flow. 126 There are a number of guidelines specified in 127 [I-D.ietf-dart-dscp-rtp] that should be followed when marking traffic 128 sent by WebRTC applications, as it is common for multiple RTP streams 129 to be multiplexed on the same transport flow. Generally, the RTP 130 streams would be marked with a value as appropriate from Table 1. A 131 WebRTC application might multiplex data channel traffic over the same 132 5-tuple as RTP streams, which would also be marked as per that table. 133 The guidance in [I-D.ietf-dart-dscp-rtp] indicates that all data 134 channel traffic would be marked with a single value that is different 135 than the value(s) used for RTP streams multiplexed with the data 136 channel traffic over the same 5-tuple, assuming RTP streams are 137 marked with a value other than default forwarding (DF). 139 In the event that RTP streams are carried over a reliable transport 140 (e.g., TCP), all such packets, even there are multiple RTP streams 141 that would be marked differently if sent via an unreliable transport, 142 must be marked with a single DSCP value. 144 This specification does not change or override the advice in any 145 other standards about setting packet markings. It simply selects a 146 subset of DSCP values that is relevant in the RTCWeb context. In 147 some cases, such as DSCP where the normative RFC leaves open multiple 148 options from which to choose, this clarifies which values should be 149 used in the RTCWeb context. This document also specifies the inputs 150 that are needed by the browser to provide to the media engine. 152 The DSCP value set by the endpoint is not always trusted by the 153 network. Therefore, the DSCP value may be remarked at any place in 154 the network for a variety of reasons to any other DSCP value, 155 including default forwarding (DF) value to provide basic best effort 156 service. The mitigation for such action is through an authorization 157 mechanism. Such authorization mechanism is outside the scope of this 158 document. There is benefit in marking traffic even if it only 159 benefits the first few hops. 161 3. Terminology 163 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" 164 in this document are to be interpreted as described in [RFC2119]. 166 4. Inputs 168 The below uses the concept of a media flow, however this is usually 169 not equivalent to a transport flow defined by a 5-tuple (source 170 address, destination address, source port, destination port, and 171 protocol). Instead each media flow contains all the packets 172 associated with an independent media entity within one 5-tuple. 173 There may be multiple media flows within the same 5-tuple. These 174 media flows might consist of different media types and have different 175 levels of importance to the application and, therefore, each 176 potentially marked using different DSCP values than for another media 177 flow multiplexed over the same transport flow. The following are the 178 inputs that the browser provides to the media engine: 180 o Data 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. 183 o Application Priority: Another input is the relative importance of 184 the flow within that data type. Many applications have multiple 185 media flows of the same data type and often some flows are more 186 important than others. For example, in a video conference where 187 there are usually audio and video flows, the audio flow may be 188 more important than the video flow. JavaScript applications can 189 tell the browser whether a particular media flow is high, medium, 190 low or very low importance to the application. 192 [I-D.ietf-rtcweb-transports] defines in more detail what an 193 individual media flow is within the WebRTC context. 195 As an example of different media flows that might be multiplexed over 196 the same transport flow, packets related to one RTP stream (e.g., an 197 audio flow) carried over UDP might be one media flow, packets related 198 to a second RTP stream (e.g., presentation video) carried over UDP 199 might be a second media flow, and finally data channel packets 200 carried via SCTP over DTLS might be third media flow. 202 5. DSCP Mappings 204 Below is a table of DSCP markings for each data type of interest to 205 RTCWeb. These DSCP values for each data type listed are a reasonable 206 subset of code point values taken from [RFC4594]. A web browser 207 SHOULD use these values to mark the appropriate media packets. More 208 information on EF can be found in [RFC3246]. More information on AF 209 can be found in [RFC2597]. DF is default forwarding which provides 210 the basic best effort service. 212 +---------------------------+-------+------+------------+-----------+ 213 | Data Type | Very | Low | Medium | High | 214 | | Low | | | | 215 +---------------------------+-------+------+------------+-----------+ 216 | Audio | CS1 | DF | EF (46) | EF (46) | 217 | | (8) | (0) | | | 218 | | | | | | 219 | Interactive Video with or | CS1 | DF | AF42, AF43 | AF41, | 220 | without audio | (8) | (0) | (36, 38) | AF42 (34, | 221 | | | | | 36) | 222 | | | | | | 223 | Non-Interactive Video | CS1 | DF | AF32, AF33 | AF31, | 224 | with or without audio | (8) | (0) | (28, 30) | AF32 (26, | 225 | | | | | 28) | 226 | | | | | | 227 | Data | CS1 | DF | AF1x (10, | AF2x (18, | 228 | | (8) | (0) | 12, 14) | 20, 22) | 229 +---------------------------+-------+------+------------+-----------+ 231 Table 1 233 The columns "very low", "low", "Medium" and "high" signify the 234 relative importance of the media flow within the application and is 235 an input that the browser receives to assist it in selecting the DSCP 236 value. These are referred to as application priority in this 237 document. Application priority does not refer to priority in the 238 network transport. 240 The browser SHOULD first select the data type of the media flow. 241 Within the data type, the relative importance of the media flow 242 SHOULD be used to select the appropriate DSCP value. All packets 243 within a media flow SHOULD have the same application priority. In 244 some cases, the selected cell may have multiple DSCP values, such as 245 AF41 and AF42. These offer different drop precedences. One may 246 select difference drop precedences for the different packets in the 247 same media flow. Therefore, all packets in the media flow SHOULD be 248 marked with the same application priority, but can have difference 249 drop precedences. 251 The combination of data type and application priority provides 252 specificity and helps in selecting the right DSCP value for the media 253 flow. In some cases, the different drop precedence values provides 254 additional granularity in classifying packets within a media flow. 255 For example, in a video conference, the video media flow may have 256 medium application priority. If so, either AF42 or AF43 may be 257 selected. If the I-frames in the stream are more important than the 258 P-frames, then the I-frames can be marked with AF42 and the P-frames 259 marked with AF43. 261 If a packet enters a QoS domain that has no support for the above 262 defined data types/application priority (service class), then the 263 network node at the edge will remark the DSCP value based on 264 policies. This could result in the media flow not getting the 265 network treatment it expects based on the original DSCP value in the 266 packet. Subsequently, if the packet enters a QoS domain that 267 supports a larger number of service classes, there may not be 268 sufficient information in the packet to restore the original 269 markings. Mechanisms for restoring such original DSCP is outside the 270 scope of this document. 272 The above table assumes that packets marked with CS1 are treated as 273 "less than best effort". However, the treatment of CS1 is 274 implementation dependent. If an implementation treats CS1 as other 275 than "less than best effort", then the actual priority (or, more 276 precisely, the per-hop-behavior) of the packets may be changed from 277 what is intended. Implementers should also note that the excess EF 278 traffic is dropped. This could mean that a packet marked as EF may 279 not get through as opposed to a packet marked with a different DSCP 280 value. 282 In summary, there are no guarantees or promised level of service with 283 the use of DSCP. The service provided to a packet is dependent upon 284 the network design along the path, as well as the congestion levels 285 at every hop. 287 6. Security Considerations 289 This specification does not add any additional security implication 290 other than the normal application use of DSCP. For security 291 implications on use of DSCP, please refer to Section 6 of RFC 4594. 292 Please also see [I-D.ietf-rtcweb-security] as an additional 293 reference. 295 7. IANA Considerations 297 This specification does not require any actions from IANA. 299 8. Downward References 301 This specification contains a downwards reference to [RFC4594]. 302 However, the parts of that RFC used by this specification are 303 sufficiently stable for this downward reference. 305 9. Acknowledgements 307 Thanks To David Black, Magnus Westerland, Paolo Severini, Jim 308 Hasselbrook, Joe Marcus, and Erik Nordmark for their help. 310 10. Document History 312 Note to RFC Editor: Please remove this section. 314 This document was originally an individual submission in RTCWeb WG. 315 The RTCWeb working group selected it to be become a WG document. 316 Later the transport ADs requested that this be moved to the TSVWG WG 317 as that seemed to be a better match. This document is now being 318 submitted as individual submission to the TSVWG with the hope that WG 319 will select it as a WG draft and move it forward to an RFC. 321 11. References 323 11.1. Normative References 325 [I-D.ietf-dart-dscp-rtp] 326 Black, D. and P. Jones, "Differentiated Services 327 (DiffServ) and Real-time Communication", draft-ietf-dart- 328 dscp-rtp-10 (work in progress), November 2014. 330 [I-D.ietf-rtcweb-security] 331 Rescorla, E., "Security Considerations for WebRTC", draft- 332 ietf-rtcweb-security-07 (work in progress), July 2014. 334 [I-D.ietf-rtcweb-transports] 335 Alvestrand, H., "Transports for WebRTC", draft-ietf- 336 rtcweb-transports-08 (work in progress), February 2015. 338 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 339 Requirement Levels", BCP 14, RFC 2119, March 1997. 341 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 342 Guidelines for DiffServ Service Classes", RFC 4594, August 343 2006. 345 11.2. Informative References 347 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 348 "Definition of the Differentiated Services Field (DS 349 Field) in the IPv4 and IPv6 Headers", RFC 2474, December 350 1998. 352 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 353 "Assured Forwarding PHB Group", RFC 2597, June 1999. 355 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 356 J., Courtney, W., Davari, S., Firoiu, V., and D. 357 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 358 Behavior)", RFC 3246, March 2002. 360 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 361 Jacobson, "RTP: A Transport Protocol for Real-Time 362 Applications", STD 64, RFC 3550, July 2003. 364 [W3C.REC-html5-20141028] 365 Hickson, I., Berjon, R., Faulkner, S., Leithead, T., 366 Navara, E., O'Connor, E., and S. Pfeiffer, "HTML5", 367 World Wide Web Consortium Recommendation REC- 368 html5-20141028, October 2014, 369 . 371 Authors' Addresses 373 Subha Dhesikan 374 Cisco Systems 376 Email: sdhesika@cisco.com 378 Cullen Jennings 379 Cisco Systems 381 Email: fluffy@cisco.com 382 Dan Druta (editor) 383 AT&T 385 Email: dd5826@att.com 387 Paul E. Jones 388 Cisco Systems 390 Email: paulej@packetizer.com 392 James Polk 393 Cisco Systems 395 Email: jmpolk@cisco.com