DSCP and other packet markings for RTCWeb QoS
draft-dhesikan-tsvwg-rtcweb-qos-03

Network Working Group                                        S. Dhesikan
Internet-Draft                                                     Cisco
Intended status: Standards Track                           D. Druta, Ed.
Expires: June 17, 2014                                               ATT
                                                                P. Jones
                                                                 J. Polk
                                                                   Cisco
                                                       December 14, 2013

             DSCP and other packet markings for RTCWeb QoS
                   draft-dhesikan-tsvwg-rtcweb-qos-03

Abstract

   Many networks, such as service provider and enterprise networks, can
   provide per packet treatments based on Differentiated Services Code
   Points (DSCP) on a per hop basis.  This document provides the
   recommended DSCP values for browsers to use for various classes of
   traffic.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 17, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Relation to Other Standards . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Inputs  . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Downward References . . . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   10. Document History  . . . . . . . . . . . . . . . . . . . . . .   5
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     11.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Differentiated Services Code Points (DSCP)[RFC2474] style packet
   marking can help provide QoS in some environments.  There are many
   use cases where such marking does not help, but it seldom makes
   things worse if packets are marked appropriately.  In other words, if
   too many packets, say all audio or all audio and video, are marked
   for a given network condition then it can prevent desirable results.
   Either too much other traffic will be starved, or there is not enough
   capacity for the preferentially marked packets (i.e., audio and/or
   video).

   This draft proposes how a browser and other VoIP applications can
   mark packets.  This draft does not contradict or redefine any advice
   from previous IETF RFCs but simply provides a simple set of
   recommendations for implementers based on the previous RFCs.

   There are some environments where priority markings frequently help.
   These include:

   1.  Private networks (Wide Area).

   2.  If the congested link is the broadband uplink in a Cable or DSL
   scenario, often residential routers/NAT support preferential
   treatment based on DSCP.

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   3.  If the congested link is a local WiFi network, marking may help.

   Traditionally DSCP values have been thought of as being site
   specific, with each site selecting its own code points for each QoS
   level.  However in the RTCWeb use cases, the browsers need to set
   them to something when there is no site specific information.  This
   document describes a reasonable default set of DSCP code point values
   drawn from existing RFCs and common usage.  These code points are
   solely defaults.  Future drafts may define mechanisms for site
   specific mappings to override the values provided in this draft.

   This draft defines some inputs that the browser can look at to
   determine how to set the various packet markings and defines the
   mapping from abstract QoS policies (data type, priority level) to
   those packet markings.

2.  Relation to Other Standards

   This specification does not change or override the advice in any
   other standards about setting packet markings.  It simply provides a
   summary of them and provides the context of how they relate into the
   RTCWeb context.  In some cases, such as DSCP where the normative RFC
   leaves open multiple options to choose from, this clarifies which
   choice should be used in the RTCWeb context.  This document also
   specifies the inputs that are needed by browser to provide to the
   media engine.

3.  Terminology

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   in this document are to be interpreted as described in [RFC2119].

4.  Inputs

   The following are the inputs that the browser provides to the media
   engine:

   o  Data Type: The browser provides this input as it knows if the flow
      is audio, interactive video with or without audio, non-interactive
      video with or without audio, or data.
   o  Priority: Another input is the relative treatment of the stream
      within that data type.  Many applications have multiple video
      flows and often some are more important than others.  Likewise, in
      a videoconference where the audio and video streams of the
      conference is of the same data type, the audio stream may be more
      important than the video stream.  JavaScript applications can tell
      the browser whether a particular media flow is high, medium, low
      or very low importance to the application.

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   Multiplexing behaviour of multiple media streams onto a single
   5-tuple is covered in draft-ietf-mmusic-sdp-mux-attributes and is not
   in the scope for this document.

5.  DSCP Mappings

   Below is a table of DSCP markings for each data type of interest to
   RTCWeb.  These DSCPs for each data type listed are a reasonable
   default set of code point values taken from [RFC4594].  A web browser
   SHOULD use these values to mark the appropriate media packets.  More
   information on EF can be found in [RFC3246].  More information on AF
   can be found in [RFC2597].

   +------------------------+-------+------+-------------+-------------+
   |       Data Type        |  Very | Low  |    Medium   |     High    |
   |                        |  Low  |      |             |             |
   +------------------------+-------+------+-------------+-------------+
   |         Audio          |  CS1  |  BE  |   EF (46)   |   EF (46)   |
   |                        |  (8)  | (0)  |             |             |
   |                        |       |      |             |             |
   | Interactive Video with |  CS1  |  BE  |  AF42, AF43 |  AF41, AF42 |
   |    or without audio    |  (8)  | (0)  |   (36, 38)  |   (34, 36)  |
   |                        |       |      |             |             |
   | Non-Interactive Video  |  CS1  |  BE  |  AF32, AF33 |  AF31, AF32 |
   | with or without audio  |  (8)  | (0)  |   (28, 30)  |   (26, 28)  |
   |                        |       |      |             |             |
   |          Data          |  CS1  |  BE  |  AF1x (10,  |  AF2x (18,  |
   |                        |  (8)  | (0)  |   12, 14)   |   20, 22)   |
   +------------------------+-------+------+-------------+-------------+

                                  Table 1

   The combination of priority input and multiple precedence levels
   within a data class provides flexibility for an implementation in
   deciding the importance of the stream and packets within a stream.
   For example, if I frames are more important than the P frames then
   the I frames can be marked with a DSCP with the lower drop
   precedence.

6.  Security Considerations

   This draft does not add any additional security implication other
   than the normal application use of DSCP.  For security implications
   on use of DSCP, please refer to Section 6 of RFC 4594 . Please also
   see work-in-progress draft draft-ietf-rtcweb-security-04 as an
   additional reference.

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7.  IANA Considerations

   This specification does not require any actions from IANA.

8.  Downward References

   This specification contains a downwards reference to [RFC4594]
   however the parts of that RFC used by this specification are
   sufficiently stable for this downward reference.

9.  Acknowledgements

   Cullen Jennings was one of the authors of this text in the original
   individual submission but was unceremoniously kicked off by the
   chairs when it became a WG version.  Thanks for hints on code to do
   this from Paolo Severini, Jim Hasselbrook, Joe Marcus, and Erik
   Nordmark.

10.  Document History

   Note to RFC Editor: Please remove this section.

   This document was originally an individual submission in RTCWeb WG.
   The RTCWeb working group selected it to be become a WG document.
   Later the transport ADs requested that this be moved to the TSVWG WG
   as that seemed to be a better match.  This document is now being
   submitted as individual submission to the TSVWG with the hope that WG
   will select it as a WG draft and move it forward to an RFC.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
              Guidelines for DiffServ Service Classes", RFC 4594, August
              2006.

11.2.  Informative References

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474, December
              1998.

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   [RFC2597]  Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
              "Assured Forwarding PHB Group", RFC 2597, June 1999.

   [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
              J., Courtney, W., Davari, S., Firoiu, V., and D.
              Stiliadis, "An Expedited Forwarding PHB (Per-Hop
              Behavior)", RFC 3246, March 2002.

Authors' Addresses

   Subha Dhesikan
   Cisco

   Email: sdhesika@cisco.com

   Dan Druta (editor)
   ATT

   Email: dd5826@att.com

   Paul Jones
   Cisco

   Email: paulej@packetizer.com

   James Polk
   Cisco

   Email: jmpolk@cisco.com

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