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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (June 23, 2014) is 3593 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 168, 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 C. Jennings 4 Intended status: Standards Track Cisco 5 Expires: December 25, 2014 D. Druta, Ed. 6 ATT 7 P. Jones 8 J. Polk 9 Cisco 10 June 23, 2014 12 DSCP and other packet markings for RTCWeb QoS 13 draft-ietf-tsvwg-rtcweb-qos-01 15 Abstract 17 Many networks, such as service provider and enterprise networks, can 18 provide per packet treatments based on Differentiated Services Code 19 Points (DSCP) on a per-hop basis. This document provides the 20 recommended DSCP values for browsers to use for various classes of 21 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 December 25, 2014. 40 Copyright Notice 42 Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 4 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 63 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 64 8. Downward References . . . . . . . . . . . . . . . . . . . . . 6 65 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 66 10. Document History . . . . . . . . . . . . . . . . . . . . . . 6 67 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 68 11.1. Normative References . . . . . . . . . . . . . . . . . . 6 69 11.2. Informative References . . . . . . . . . . . . . . . . . 6 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 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 draft proposes how WebRTC applications can mark packets. This 85 draft does not contradict or redefine any advice from previous IETF 86 RFCs but simply provides a simple set of recommendations for 87 implementers based on the previous RFCs. 89 There are some environments where priority markings frequently help. 90 These include: 92 1. Private networks (Wide Area). 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 WiFi network, 99 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 each QoS 103 level. However in the RTCWeb use cases, the browsers need to set 104 them to something when there is no site specific information. 105 Browsers, in this document is used synonmously with "interactive User 106 Agent" as defined in teh HTML specification, [W3C.WD-html-20110525]. 107 This document describes a reasonable default set of DSCP code point 108 values drawn from existing RFCs and common usage. These code points 109 are solely defaults. Future drafts may define mechanisms for site 110 specific mappings to override the values provided in this draft. 112 This draft defines some inputs that the browser in an WebRTC 113 application can look at to determine how to set the various packet 114 markings and defines the mapping from abstract QoS policies (data 115 type, priority level) to those packet markings. 117 2. Relation to Other Standards 119 This specification does not change or override the advice in any 120 other standards about setting packet markings. It simply provides a 121 summary of them and provides the context of how they relate in the 122 RTCWeb context. In some cases, such as DSCP where the normative RFC 123 leaves open multiple options from which to choose, this clarifies 124 which choice should be used in the RTCWeb context. This document 125 also specifies the inputs that are needed by the browser to provide 126 to the media engine. 128 The DSCP value set by the endpoint is not always trusted by the 129 network. Therefore, the DSCP value may be remarked at the network 130 edge through policy to any other DSCP value, including best effort. 131 The mitigation for such action is through an authorization mechanism. 132 Such authorization mechanism is outside the scope of this document. 134 3. Terminology 136 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" 137 in this document are to be interpreted as described in [RFC2119]. 139 4. Inputs 141 The below uses the concept of a media flow, however these are 142 commonly not equivalent to a transport flow, i.e. as defined by a 143 5-tuple (source address, destination address, source port, 144 destination port, and protocol). Instead each media flow contains 145 all the packets associated with an independent media entity within 146 one 5-tuple. There may be multiple media flows within the same 5- 147 tuple. These media flows might consist of different media types and 148 have different priorities. The following are the inputs that the 149 browser provides to the media engine: 151 o Data Type: The browser provides this input as it knows if the flow 152 is audio, interactive video with or without audio, non-interactive 153 video with or without audio, or data. 154 o Priority: Another input is the relative treatment of the flow 155 within that data type. Many applications have multiple media 156 flows of the same data type and often some are more important than 157 others. Likewise, in a video conference where the flows in the 158 conference is of the same data type but contains different media 159 types, the flow for audio may be more important than the video 160 flow. JavaScript applications can tell the browser whether a 161 particular media flow is high, medium, low or very low importance 162 to the application. 164 When it comes to data transmission, a media (data) flow is the SCTP 165 stream under a common congestion control (currently within the same 166 SCTP association). 168 [I-D.ietf-rtcweb-transports] defines in more detail what an 169 individual media flow is within the WebRTC context. 171 5. DSCP Mappings 173 Below is a table of DSCP markings for each data type of interest to 174 RTCWeb. These DSCP values for each data type listed are a reasonable 175 default set of code point values taken from [RFC4594]. A web browser 176 SHOULD use these values to mark the appropriate media packets. More 177 information on EF can be found in [RFC3246]. More information on AF 178 can be found in [RFC2597]. 180 +---------------------------+-------+------+------------+-----------+ 181 | Data Type | Very | Low | Medium | High | 182 | | Low | | | | 183 +---------------------------+-------+------+------------+-----------+ 184 | Audio | CS1 | BE | EF (46) | EF (46) | 185 | | (8) | (0) | | | 186 | | | | | | 187 | Interactive Video with or | CS1 | BE | AF42, AF43 | AF41, | 188 | without audio | (8) | (0) | (36, 38) | AF42 (34, | 189 | | | | | 36) | 190 | | | | | | 191 | Non-Interactive Video | CS1 | BE | AF32, AF33 | AF31, | 192 | with or without audio | (8) | (0) | (28, 30) | AF32 (26, | 193 | | | | | 28) | 194 | | | | | | 195 | Data | CS1 | BE | AF1x (10, | AF2x (18, | 196 | | (8) | (0) | 12, 14) | 20, 22) | 197 +---------------------------+-------+------+------------+-----------+ 199 Table 1 201 The columns "very low", "low", "Medium" and "high" are the priority 202 levels. The browser SHOULD first select the data type of the media 203 flow. Within the data type, the priority of the media flow SHOULD be 204 selected. All packets within a media flow SHOULD have the same 205 priority. In some cases, the selected cell may have multiple DSCP 206 values, such as AF41 and AF42. These offer different drop 207 precedences. One may select difference drop precedences for the 208 different packets in the media flow. Therefore, all packets in the 209 stream SHOULD be marked with the same priority but can have 210 difference drop precedences. 212 The combination of data type and priority provides specificity and 213 helps in selecting the right DSCP value for the media flow. In some 214 cases, the different drop precedence values provides additional 215 granularity in classifying packets within a media flow. For example, 216 in a video conference, the video media flow may be medium priority. 217 If so, either AF42 or AF43 may be selected. If the I frames in the 218 stream are more important than the P frames then the I frames can be 219 marked with AF42 and the P frames marked with AF43. 221 The above table assumes that packets marked with CS1 is treated as 222 "less than best effort". However, the treatment of CS1 is 223 implementation dependent. If an implementation treats CS1 as other 224 than "less than best effort", then the priority of the packets may be 225 changed from what is intended. 227 If a packet enters a QoS domain that has no support for the above 228 defined Data Types/Application (service) classes, then the network 229 node at the edge will remark the DSCP value based on policies. 230 Subsequently, if the packet enters a QoS domain that supports a 231 larger number of Data types/Application (service) classes, there may 232 not be sufficient information in the packet to restore the original 233 markings. Mechanisms for restoring such original DSCP is outside the 234 scope of this document. 236 6. Security Considerations 237 This draft does not add any additional security implication other 238 than the normal application use of DSCP. For security implications 239 on use of DSCP, please refer to Section 6 of RFC 4594. Please also 240 see work-in-progress draft draft-ietf-rtcweb-security-04 as an 241 additional reference. 243 7. IANA Considerations 245 This specification does not require any actions from IANA. 247 8. Downward References 249 This specification contains a downwards reference to [RFC4594] 250 however the parts of that RFC used by this specification are 251 sufficiently stable for this downward reference. 253 9. Acknowledgements 255 Cullen Jennings was one of the authors of this text in the original 256 individual submission but was unceremoniously kicked off by the 257 chairs when it became a WG version. Thanks To David Black, Magnus 258 Westerland, Paolo Severini, Jim Hasselbrook, Joe Marcus, and Erik 259 Nordmark for their help. 261 10. Document History 263 Note to RFC Editor: Please remove this section. 265 This document was originally an individual submission in RTCWeb WG. 266 The RTCWeb working group selected it to be become a WG document. 267 Later the transport ADs requested that this be moved to the TSVWG WG 268 as that seemed to be a better match. This document is now being 269 submitted as individual submission to the TSVWG with the hope that WG 270 will select it as a WG draft and move it forward to an RFC. 272 11. References 274 11.1. Normative References 276 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 277 Requirement Levels", BCP 14, RFC 2119, March 1997. 279 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 280 Guidelines for DiffServ Service Classes", RFC 4594, August 281 2006. 283 11.2. Informative References 285 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 286 "Definition of the Differentiated Services Field (DS 287 Field) in the IPv4 and IPv6 Headers", RFC 2474, December 288 1998. 290 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 291 "Assured Forwarding PHB Group", RFC 2597, June 1999. 293 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 294 J., Courtney, W., Davari, S., Firoiu, V., and D. 295 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 296 Behavior)", RFC 3246, March 2002. 298 Authors' Addresses 300 Subha Dhesikan 301 Cisco 303 Email: sdhesika@cisco.com 305 Cullen Jennings 306 Cisco 308 Email: fluffy@cisco.com 310 Dan Druta (editor) 311 ATT 313 Email: dd5826@att.com 315 Paul Jones 316 Cisco 318 Email: paulej@packetizer.com 320 James Polk 321 Cisco 323 Email: jmpolk@cisco.com