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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (April 2, 2014) is 3678 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) == Missing Reference: 'I-D.ietf-rtcweb-transports' is mentioned on line 167, but not defined ** Downref: Normative reference to an Informational RFC: RFC 4594 Summary: 1 error (**), 0 flaws (~~), 3 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 Cisco 4 Intended status: Standards Track D. Druta, Ed. 5 Expires: October 4, 2014 ATT 6 P. Jones 7 J. Polk 8 Cisco 9 April 2, 2014 11 DSCP and other packet markings for RTCWeb QoS 12 draft-ietf-tsvwg-rtcweb-qos-00 14 Abstract 16 Many networks, such as service provider and enterprise networks, can 17 provide per packet treatments based on Differentiated Services Code 18 Points (DSCP) on a per-hop basis. This document provides the 19 recommended DSCP values for browsers to use for various classes of 20 traffic. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on October 4, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Relation to Other Standards . . . . . . . . . . . . . . . . . 3 58 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 4 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 62 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 63 8. Downward References . . . . . . . . . . . . . . . . . . . . . 6 64 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 65 10. Document History . . . . . . . . . . . . . . . . . . . . . . 6 66 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 11.1. Normative References . . . . . . . . . . . . . . . . . . 7 68 11.2. Informative References . . . . . . . . . . . . . . . . . 7 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 71 1. Introduction 73 Differentiated Services Code Points (DSCP)[RFC2474] style packet 74 marking can help provide QoS in some environments. There are many 75 use cases where such marking does not help, but it seldom makes 76 things worse if packets are marked appropriately. In other words, if 77 too many packets, say all audio or all audio and video, are marked 78 for a given network condition then it can prevent desirable results. 79 Either too much other traffic will be starved, or there is not enough 80 capacity for the preferentially marked packets (i.e., audio and/or 81 video). 83 This draft proposes how WebRTC applications can mark packets. This 84 draft does not contradict or redefine any advice from previous IETF 85 RFCs but simply provides a simple set of recommendations for 86 implementers based on the previous RFCs. 88 There are some environments where priority markings frequently help. 89 These include: 91 1. Private networks (Wide Area). 93 2. Residential Networks: If the congested link is the broadband 94 uplink in a Cable or DSL scenario, often residential routers/NAT 95 support preferential treatment based on DSCP. 97 3. Wireless Networks: If the congested link is a local WiFi network, 98 marking may help. 100 Traditionally DSCP values have been thought of as being site 101 specific, with each site selecting its own code points for each QoS 102 level. However in the RTCWeb use cases, the browsers need to set 103 them to something when there is no site specific information. 104 Browsers, in this document is used synonmously with "interactive User 105 Agent" as defined in teh HTML specification, [W3C.WD-html-20110525]. 106 This document describes a reasonable default set of DSCP code point 107 values drawn from existing RFCs and common usage. These code points 108 are solely defaults. Future drafts may define mechanisms for site 109 specific mappings to override the values provided in this draft. 111 This draft defines some inputs that the browser in an WebRTC 112 application can look at to determine how to set the various packet 113 markings and defines the mapping from abstract QoS policies (data 114 type, priority level) to those packet markings. 116 2. Relation to Other Standards 118 This specification does not change or override the advice in any 119 other standards about setting packet markings. It simply provides a 120 summary of them and provides the context of how they relate in the 121 RTCWeb context. In some cases, such as DSCP where the normative RFC 122 leaves open multiple options from which to choose, this clarifies 123 which choice should be used in the RTCWeb context. This document 124 also specifies the inputs that are needed by the browser to provide 125 to the media engine. 127 The DSCP value set by the endpoint is not always trusted by the 128 network. Therefore, the DSCP value may be remarked at the network 129 edge through policy to any other DSCP value, including best effort. 130 The mitigation for such action is through an authorization mechanism. 131 Such authorization mechanism is outside the scope of this document. 133 3. Terminology 135 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" 136 in this document are to be interpreted as described in [RFC2119]. 138 4. Inputs 140 The below uses the concept of a media flow, however these are 141 commonly not equivalent to a transport flow, i.e. as defined by a 142 5-tuple (source address, destination address, source port, 143 destination port, and protocol). Instead each media flow contains 144 all the packets associated with an independent media entity within 145 one 5-tuple. There may be multiple media flows within the same 5- 146 tuple. These media flows might consist of different media types and 147 have different priorities. The following are the inputs that the 148 browser provides to the media engine: 150 o Data Type: The browser provides this input as it knows if the flow 151 is audio, interactive video with or without audio, non-interactive 152 video with or without audio, or data. 153 o Priority: Another input is the relative treatment of the flow 154 within that data type. Many applications have multiple media 155 flows of the same data type and often some are more important than 156 others. Likewise, in a video conference where the flows in the 157 conference is of the same data type but contains different media 158 types, the flow for audio may be more important than the video 159 flow. JavaScript applications can tell the browser whether a 160 particular media flow is high, medium, low or very low importance 161 to the application. 163 When it comes to data transmission, a media (data) flow is the SCTP 164 stream under a common congestion control (currently within the same 165 SCTP association). 167 [I-D.ietf-rtcweb-transports] defines in more detail what an 168 individual media flow is within the WebRTC context. 170 5. DSCP Mappings 172 Below is a table of DSCP markings for each data type of interest to 173 RTCWeb. These DSCP values for each data type listed are a reasonable 174 default set of code point values taken from [RFC4594]. A web browser 175 SHOULD use these values to mark the appropriate media packets. More 176 information on EF can be found in [RFC3246]. More information on AF 177 can be found in [RFC2597]. 179 +------------------------+-------+------+-------------+-------------+ 180 | Data Type | Very | Low | Medium | High | 181 | | Low | | | | 182 +------------------------+-------+------+-------------+-------------+ 183 | Audio | CS1 | BE | EF (46) | EF (46) | 184 | | (8) | (0) | | | 185 | | | | | | 186 | Interactive Video with | CS1 | BE | AF42, AF43 | AF41, AF42 | 187 | or without audio | (8) | (0) | (36, 38) | (34, 36) | 188 | | | | | | 189 | Non-Interactive Video | CS1 | BE | AF32, AF33 | AF31, AF32 | 190 | with or without audio | (8) | (0) | (28, 30) | (26, 28) | 191 | | | | | | 192 | Data | CS1 | BE | AF1x (10, | AF2x (18, | 193 | | (8) | (0) | 12, 14) | 20, 22) | 194 +------------------------+-------+------+-------------+-------------+ 196 Table 1 198 The columns "very low", "low", "Medium" and "high" are the priority 199 levels. The browser SHOULD first select the data type of the media 200 flow. Within the data type, the priority of the media flow SHOULD be 201 selected. All packets within a media flow SHOULD have the same 202 priority. In some cases, the selected cell may have multiple DSCP 203 values, such as AF41 and AF42. These offer different drop 204 precedences. One may select difference drop precedences for the 205 different packets in the media flow. Therefore, all packets in the 206 stream SHOULD be marked with the same priority but can have 207 difference drop precedences. 209 The combination of data type and priority provides specificity and 210 helps in selecting the right DSCP value for the media flow. In some 211 cases, the different drop precedence values provides additional 212 granularity in classifying packets within a media flow. For example, 213 in a video conference, the video media flow may be medium priority. 214 If so, either AF42 or AF43 may be selected. If the I frames in the 215 stream are more important than the P frames then the I frames can be 216 marked with AF42 and the P frames marked with AF43. 218 The above table assumes that packets marked with CS1 is treated as 219 "less than best effort". However, the treatment of CS1 is 220 implementation dependent. If an implementation treats CS1 as other 221 than "less than best effort", then the priority of the packets may be 222 changed from what is intended. 224 If a packet enters a QoS domain that has no support for the above 225 defined Data Types/Application (service) classes, then the network 226 node at the edge will remark the DSCP value based on policies. 228 Subsequently, if the packet enters a QoS domain that supports a 229 larger number of Data types/Application (service) classes, there may 230 not be sufficient information in the packet to restore the original 231 markings. Mechanisms for restoring such original DSCP is outside the 232 scope of this document. 234 6. Security Considerations 236 This draft does not add any additional security implication other 237 than the normal application use of DSCP. For security implications 238 on use of DSCP, please refer to Section 6 of RFC 4594. Please also 239 see work-in-progress draft draft-ietf-rtcweb-security-04 as an 240 additional reference. 242 7. IANA Considerations 244 This specification does not require any actions from IANA. 246 8. Downward References 248 This specification contains a downwards reference to [RFC4594] 249 however the parts of that RFC used by this specification are 250 sufficiently stable for this downward reference. 252 9. Acknowledgements 254 Cullen Jennings was one of the authors of this text in the original 255 individual submission but was unceremoniously kicked off by the 256 chairs when it became a WG version. Thanks To David Black, Magnus 257 Westerland, Paolo Severini, Jim Hasselbrook, Joe Marcus, and Erik 258 Nordmark for their help. 260 10. Document History 262 Note to RFC Editor: Please remove this section. 264 This document was originally an individual submission in RTCWeb WG. 265 The RTCWeb working group selected it to be become a WG document. 266 Later the transport ADs requested that this be moved to the TSVWG WG 267 as that seemed to be a better match. This document is now being 268 submitted as individual submission to the TSVWG with the hope that WG 269 will select it as a WG draft and move it forward to an RFC. 271 11. References 272 11.1. Normative References 274 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 275 Requirement Levels", BCP 14, RFC 2119, March 1997. 277 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 278 Guidelines for DiffServ Service Classes", RFC 4594, August 279 2006. 281 11.2. Informative References 283 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 284 "Definition of the Differentiated Services Field (DS 285 Field) in the IPv4 and IPv6 Headers", RFC 2474, December 286 1998. 288 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 289 "Assured Forwarding PHB Group", RFC 2597, June 1999. 291 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 292 J., Courtney, W., Davari, S., Firoiu, V., and D. 293 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 294 Behavior)", RFC 3246, March 2002. 296 Authors' Addresses 298 Subha Dhesikan 299 Cisco 301 Email: sdhesika@cisco.com 303 Dan Druta (editor) 304 ATT 306 Email: dd5826@att.com 308 Paul Jones 309 Cisco 311 Email: paulej@packetizer.com 313 James Polk 314 Cisco 316 Email: jmpolk@cisco.com