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Versions: (draft-ietf-rtcweb-qos) 00 01 02 03 04 05 06 07 draft-ietf-tsvwg-rtcweb-qos

Network Working Group                                        S. Dhesikan
Internet-Draft                                               C. Jennings
Intended status: Standards Track                                   Cisco
Expires: December 24, 2014                                 D. Druta, Ed.
                                                                     ATT
                                                                P. Jones
                                                                 J. Polk
                                                                   Cisco
                                                           June 22, 2014


             DSCP and other packet markings for RTCWeb QoS
                   draft-dhesikan-tsvwg-rtcweb-qos-07

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 24, 2014.

Copyright Notice

   Copyright (c) 2014 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   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 . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Downward References . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. Document History  . . . . . . . . . . . . . . . . . . . . . .   6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     11.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

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 WebRTC 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 in an WebRTC
   application 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 the browser to provide to the
   media engine.

   The DSCP value set by the endpoint is not always trusted by the
   network.  Therefore, the DSCP value may be remarked to any other
   DSCP, even to best effort at the network edge through policy.  The
   mitigation for such action is through an authorization mechanism.
   Such authorization mechanism is outside the scope of this document.

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












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   The below uses the concept of a media flow, however these are
   commonly not equivalent to a transport flow, i.e. as defined by a
   5-tuple (source address, destination address, source port,
   destination port, and protocol).  Instead each media flow contains
   all the packets associated with an independent media entity within
   one 5-tuple.  There may be multiple media flows within the same 5-
   tuple.  These media flows might be consisting of different media
   types and have different priorities.  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 flow
      within that data type.  Many applications have multiple media
      flows of the same data type and often some are more important than
      others.  Likewise, in a video conference where the flows in the
      conference is of the same data type but contains different media
      types, the flow for audio may be more important than the video
      flow.  JavaScript applications can tell the browser whether a
      particular media flow is high, medium, low or very low importance
      to the application.

   When it comes to data transmission, a media (data) flow is the SCTP
   stream under a common congestion control (currently within the same
   SCTP association).

   [I-D.ietf-rtcweb-transports] defines in more detail what an
   individual media flow is within the WebRTC context.

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 or |  CS1  |  BE  | AF42, AF43 |   AF41,   |
   |       without audio       |  (8)  | (0)  |  (36, 38)  | AF42 (34, |



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   |                           |       |      |            |    36)    |
   |                           |       |      |            |           |
   |   Non-Interactive Video   |  CS1  |  BE  | AF32, AF33 |   AF31,   |
   |   with or without audio   |  (8)  | (0)  |  (28, 30)  | AF32 (26, |
   |                           |       |      |            |    28)    |
   |                           |       |      |            |           |
   |            Data           |  CS1  |  BE  | AF1x (10,  | AF2x (18, |
   |                           |  (8)  | (0)  |  12, 14)   |  20, 22)  |
   +---------------------------+-------+------+------------+-----------+

                                  Table 1

   The columns "very low", "low", "Medium" and "high" are the priority
   levels.  The browser app SHOULD first select the data type of the
   media flow.  Within the data type, the priority of the media flow
   SHOULD be selected.  All packets within a media flow SHOULD have the
   same priority.  In some cases, the selected cell may have multiple
   DSCP values, such as AF41 and AF42.  These offer different drop
   precedences.  One may select difference drop precedences for the
   different packets in the media flow.  Therefore, all packets in the
   stream SHOULD be marked with the same priority but can have
   difference drop precedences.

   The combination of data type and priority provides specificity and
   helps in selecting the right DSCP value for the media flow.  In some
   cases, the different drop precedence values provides additional
   granularity in classifying packets within a media flow.  For example:
   In a video conference, the video media flow may be medium priority.
   If so, either AF42 or AF43 may be selected.  If the I frames in the
   stream are more important than the P frames then the I frames can be
   marked with AF42 and the P frames marked with AF43.

   The above table assumes that packets marked with CS1 is treated as
   "less than best effort".  However, the treatment of CS1 is
   implementation dependent.  If an implementation treats CS1 as other
   than "less than best effort", then the priority of the packets may be
   changed from what is intended.

   If a packet enters a QoS domain that has no support for the above
   defined Data Types/Application classes, then the network node at the
   edge will remark the DSCP value based on policies.  Subsequently, if
   the packet enters a QoS domain that supports a larger number of Data
   types/Application (service) classes, there may not be sufficient
   information in the packet to restore the original markings.
   Mechanisms for restoring such original DSCP is outside the scope of
   this document.





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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.

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

   Thanks To David Black, Magnus Westerland, Paolo Severini, Jim
   Hasselbrook, Joe Marcus, and Erik Nordmark for their help.

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





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   [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.

   [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


   Cullen Jennings
   Cisco

   Email: fluffy@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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