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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (June 22, 2014) is 3595 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 164, 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 24, 2014 D. Druta, Ed. 6 ATT 7 P. Jones 8 J. Polk 9 Cisco 10 June 22, 2014 12 DSCP and other packet markings for RTCWeb QoS 13 draft-dhesikan-tsvwg-rtcweb-qos-07 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 24, 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 . . . . . . . . . . . . . . . . . . . 6 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. If the congested link is the broadband uplink in a Cable or DSL 95 scenario, often residential routers/NAT support preferential 96 treatment based on DSCP. 98 3. If the congested link is a local WiFi network, 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. This 104 document describes a reasonable default set of DSCP code point values 105 drawn from existing RFCs and common usage. These code points are 106 solely defaults. Future drafts may define mechanisms for site 107 specific mappings to override the values provided in this draft. 109 This draft defines some inputs that the browser in an WebRTC 110 application can look at to determine how to set the various packet 111 markings and defines the mapping from abstract QoS policies (data 112 type, priority level) to those packet markings. 114 2. Relation to Other Standards 116 This specification does not change or override the advice in any 117 other standards about setting packet markings. It simply provides a 118 summary of them and provides the context of how they relate into the 119 RTCWeb context. In some cases, such as DSCP where the normative RFC 120 leaves open multiple options to choose from, this clarifies which 121 choice should be used in the RTCWeb context. This document also 122 specifies the inputs that are needed by the browser to provide to the 123 media engine. 125 The DSCP value set by the endpoint is not always trusted by the 126 network. Therefore, the DSCP value may be remarked to any other 127 DSCP, even to best effort at the network edge through policy. The 128 mitigation for such action is through an authorization mechanism. 129 Such authorization mechanism is outside the scope of this document. 131 3. Terminology 133 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" 134 in this document are to be interpreted as described in [RFC2119]. 136 4. Inputs 137 The below uses the concept of a media flow, however these are 138 commonly not equivalent to a transport flow, i.e. as defined by a 139 5-tuple (source address, destination address, source port, 140 destination port, and protocol). Instead each media flow contains 141 all the packets associated with an independent media entity within 142 one 5-tuple. There may be multiple media flows within the same 5- 143 tuple. These media flows might be consisting of different media 144 types and have different priorities. The following are the inputs 145 that the browser provides to the media engine: 147 o Data Type: The browser provides this input as it knows if the flow 148 is audio, interactive video with or without audio, non-interactive 149 video with or without audio, or data. 150 o Priority: Another input is the relative treatment of the flow 151 within that data type. Many applications have multiple media 152 flows of the same data type and often some are more important than 153 others. Likewise, in a video conference where the flows in the 154 conference is of the same data type but contains different media 155 types, the flow for audio may be more important than the video 156 flow. JavaScript applications can tell the browser whether a 157 particular media flow is high, medium, low or very low importance 158 to the application. 160 When it comes to data transmission, a media (data) flow is the SCTP 161 stream under a common congestion control (currently within the same 162 SCTP association). 164 [I-D.ietf-rtcweb-transports] defines in more detail what an 165 individual media flow is within the WebRTC context. 167 5. DSCP Mappings 169 Below is a table of DSCP markings for each data type of interest to 170 RTCWeb. These DSCPs for each data type listed are a reasonable 171 default set of code point values taken from [RFC4594]. A web browser 172 SHOULD use these values to mark the appropriate media packets. More 173 information on EF can be found in [RFC3246]. More information on AF 174 can be found in [RFC2597]. 176 +---------------------------+-------+------+------------+-----------+ 177 | Data Type | Very | Low | Medium | High | 178 | | Low | | | | 179 +---------------------------+-------+------+------------+-----------+ 180 | Audio | CS1 | BE | EF (46) | EF (46) | 181 | | (8) | (0) | | | 182 | | | | | | 183 | Interactive Video with or | CS1 | BE | AF42, AF43 | AF41, | 184 | without audio | (8) | (0) | (36, 38) | AF42 (34, | 185 | | | | | 36) | 186 | | | | | | 187 | Non-Interactive Video | CS1 | BE | AF32, AF33 | AF31, | 188 | with or without audio | (8) | (0) | (28, 30) | AF32 (26, | 189 | | | | | 28) | 190 | | | | | | 191 | Data | CS1 | BE | AF1x (10, | AF2x (18, | 192 | | (8) | (0) | 12, 14) | 20, 22) | 193 +---------------------------+-------+------+------------+-----------+ 195 Table 1 197 The columns "very low", "low", "Medium" and "high" are the priority 198 levels. The browser app SHOULD first select the data type of the 199 media flow. Within the data type, the priority of the media flow 200 SHOULD be selected. All packets within a media flow SHOULD have the 201 same priority. In some cases, the selected cell may have multiple 202 DSCP values, such as AF41 and AF42. These offer different drop 203 precedences. One may select difference drop precedences for the 204 different packets in the media flow. Therefore, all packets in the 205 stream SHOULD be marked with the same priority but can have 206 difference drop precedences. 208 The combination of data type and priority provides specificity and 209 helps in selecting the right DSCP value for the media flow. In some 210 cases, the different drop precedence values provides additional 211 granularity in classifying packets within a media flow. For example: 212 In a video conference, the video media flow may be medium priority. 213 If so, either AF42 or AF43 may be selected. If the I frames in the 214 stream are more important than the P frames then the I frames can be 215 marked with AF42 and the P frames marked with AF43. 217 The above table assumes that packets marked with CS1 is treated as 218 "less than best effort". However, the treatment of CS1 is 219 implementation dependent. If an implementation treats CS1 as other 220 than "less than best effort", then the priority of the packets may be 221 changed from what is intended. 223 If a packet enters a QoS domain that has no support for the above 224 defined Data Types/Application classes, then the network node at the 225 edge will remark the DSCP value based on policies. Subsequently, if 226 the packet enters a QoS domain that supports a larger number of Data 227 types/Application (service) classes, there may not be sufficient 228 information in the packet to restore the original markings. 229 Mechanisms for restoring such original DSCP is outside the scope of 230 this document. 232 6. Security Considerations 234 This draft does not add any additional security implication other 235 than the normal application use of DSCP. For security implications 236 on use of DSCP, please refer to Section 6 of RFC 4594 . Please also 237 see work-in-progress draft draft-ietf-rtcweb-security-04 as an 238 additional reference. 240 7. IANA Considerations 242 This specification does not require any actions from IANA. 244 8. Downward References 246 This specification contains a downwards reference to [RFC4594] 247 however the parts of that RFC used by this specification are 248 sufficiently stable for this downward reference. 250 9. Acknowledgements 252 Thanks To David Black, Magnus Westerland, Paolo Severini, Jim 253 Hasselbrook, Joe Marcus, and Erik Nordmark for their help. 255 10. Document History 257 Note to RFC Editor: Please remove this section. 259 This document was originally an individual submission in RTCWeb WG. 260 The RTCWeb working group selected it to be become a WG document. 261 Later the transport ADs requested that this be moved to the TSVWG WG 262 as that seemed to be a better match. This document is now being 263 submitted as individual submission to the TSVWG with the hope that WG 264 will select it as a WG draft and move it forward to an RFC. 266 11. References 268 11.1. Normative References 270 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 271 Requirement Levels", BCP 14, RFC 2119, March 1997. 273 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 274 Guidelines for DiffServ Service Classes", RFC 4594, August 275 2006. 277 11.2. Informative References 279 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 280 "Definition of the Differentiated Services Field (DS 281 Field) in the IPv4 and IPv6 Headers", RFC 2474, December 282 1998. 284 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 285 "Assured Forwarding PHB Group", RFC 2597, June 1999. 287 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 288 J., Courtney, W., Davari, S., Firoiu, V., and D. 289 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 290 Behavior)", RFC 3246, March 2002. 292 Authors' Addresses 294 Subha Dhesikan 295 Cisco 297 Email: sdhesika@cisco.com 299 Cullen Jennings 300 Cisco 302 Email: fluffy@cisco.com 304 Dan Druta (editor) 305 ATT 307 Email: dd5826@att.com 309 Paul Jones 310 Cisco 312 Email: paulej@packetizer.com 314 James Polk 315 Cisco 317 Email: jmpolk@cisco.com