Network Working Group                                        S. Dhesikan
Internet Draft                                             Cisco Systems
Intended status: Standards Track                           D. Druta, Ed.
Expires: September 2013                                             AT&T
                                                                P. Jones
                                                                 J. Polk
                                                           Cisco Systems
                                                          March 10, 2013

               DSCP and other packet markings for RTCWeb QoS


   Many networks, such as service provider and private 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

Status of this Memo

   This Internet-Draft is submitted to IETF 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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 September 10, 2013.

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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   ( in effect on the date of
   publication of this document. Please review these documents
   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. Conventions used in this document..............................3
   4. Inputs.........................................................3
   5. DSCP Mappings..................................................4
   6. QCI Mappings...................................................5
   7. Wi-Fi Mappings.................................................5
   8. W3C API Implications...........................................6
   9. Security Considerations........................................6
   10. IANA Considerations...........................................6
   11. Downward References...........................................6
   12. Document History..............................................7
   13. References....................................................7
      13.1. Normative References.....................................7
      13.2. Informative References...................................7
   14. Acknowledgements..............................................7
   Appendix A. Code Hints............................................9

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,
   when attempting to avoid congestion by marking certain traffic flows,
   say all audio or all audio and video, marking too many audio and/or
   video flows for a given network's capacity 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)

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     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.
     3. If the congested link is a local Wi-Fi network, marking may
     4. In some cellular style deployments, markings may help in cases
        where the network does not remove them.

   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 a
   mapping from abstract QoS policies (media 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
   non-normative summary of them and provides the context of how they
   relate into the RTCWeb context.  This document also specifies the
   requirements for the W3C WebRTC API to understand what it needs to
   control, and how the control splits between things the JavaScript
   application running in the browser can control and things the browser
   needs to control.  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.

3. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

4. Inputs

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

     o Type of flow:  The browser provides this input as it knows if
       the flow is audio, video, or data. In this specification, both
       interactive and streaming media are included.  They are treated

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       in different categories as their QoS requirements are slightly

       If the type of flow is multiplexed content, then the input is a
       list of the type of flows that are multiplexed within the single

     o Session Context:  This input provides the session context for
       the type of flow.  For example, the type of flow may be audio.
       The flow may be part of a VoIP session or an audio/video
       session.  Such session context information helps the media
       engine and the underlying network to make decisions on how to
       treat the audio flow which may differ based on the entire
       session to which the flow belongs.  The browser should know this

     o Relative priority: Another input is the relative treatment of
       the stream within that session.  Many applications have multiple
       video flows and often some are more important than others.
       JavaScript applications can tell the browser whether a
       particular media flow is high, medium, or low importance to the

5. DSCP Mappings

   Below is a table of DSCP markings for each media type in which RTCWeb
   is interested.  These DSCPs for each media 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].

   In a multiplexed session the flow may either be all mapped to a
   single or to multiple DSCPs one per flow. If some networks cannot
   handle multiplexed traffic, then [I-D.ietf-rtcweb-rtp-usage] provides
   the capability to disable multiplexing.

       | Media Type            |    Low    |   Medium  |    High   |
       | Audio                 |  46 (EF)  |  46 (EF)  |  46 (EF)  |
       | Interactive Video     | 38 (AF43) | 36 (AF42) | 34 (AF41) |
       | Non-Interactive Video | 26 (AF33) | 28 (AF32) | 30 (AF31) |
       | Data                  |  8 (CS1)  |   0 (BE)  | 10 (AF11) |
             Table 1 - Media Type, Priority, and DSCP Mapping

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6. QCI Mappings

              | Media Type            | Low | Medium | High |
              | Audio                 |  1  |    1   |   1  |
              | Interactive Video     |  2  |    2   |   2  |
              | Non-Interactive Video |  8  |    6   |   4  |
              | Data                  |  9  |    9   |   3  |
              Table 2 - Media Type, Priority, and QCI Values

   This corresponds to the mapping provided in TODO REF which are:

   | Value |        |     |                     Use                    |
   | 1     |   GBR  |  2  |              Interactive Voice             |
   | 2     |   GBR  |  4  |              Interactive Video             |
   | 3     |   GBR  |  5  |            Non-Interactive Video           |
   | 4     |   GBR  |  3  |              Real Time Gaming              |
   | 5     | Non-BG | R 1 |                IMS Signaling               |
   | 6     | Non-BG | R 7 |       interactive Voice, video, games      |
   | 7-9   | Non-BG | R 6 |  non interactive video / TCP web, email, / |
   |       |        |     |            Platinum vs gold user           |
           Table 3 - Media Type, Priority, and QCI Mapping (LTE)

7. Wi-Fi Mappings

              | Media Type            | Low | Medium | High |
              | Audio                 |  6  |    6   |   6  |
              | Interactive Video     |  5  |    5   |   5  |
              | Non-Interactive Video |  4  |    4   |   4  |
              | Data                  |  1  |    0   |   3  |
          Table 4 - Media Type, Priority, and 802.1d (UP) Values

   This corresponds to the mappings from TODO REF of:

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   | Value |    |   Traffic Type   |   Access Category   | Designation |
   |       |    |                  |         (AC)        |             |
   | 1     | BK |    Background    |        AC_BK        |  Background |
   | 2     |  - |      (spare)     |        AC_BK        |  Background |
   | 0     | BE |    Best Effort   |        AC_BE        | Best Effort |
   | 3     | EE | Excellent Effort |        AC_BE        | Best Effort |
   | 4     | CL |  Controlled Load |        AC_VI        |    Video    |
   | 5     | VI |       Video      |        AC_VI        |    Video    |
   | 6     | VO |       Voice      |        AC_VO        |    Voice    |
   | 7     | NC |  Network Control |        AC_VO        |    Voice    |
          Table 5 - Wi-Fi Priority (UP) / Access Category Mapping

8. W3C API Implications

   To work with this proposal, the W3C specification SHOULD provide a
   way to specify the importance of media and data streams.

   The W3C API SHOULD also provide a way for the application to find out
   the source and destination IP and ports of any flow as well as the
   DSCP value or other markings in use for that flow.  The JavaScript
   application can then communicate this to a web service that may
   install a particular policy for that flow.

   The W3C API SHOULD NOT provide a way for the JavaScript to
   arbitrarily set the marking to any value of the JavaScript choosing
   as this reduces the security provided by the browser knowing the
   media type.

9. Security Considerations

   TODO - discuss implications of what browser can set and what
   JavaScript can set

10. IANA Considerations

   This specification does not require any actions from IANA.

11. 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.

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12. 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.

13. References

13.1. 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.

13.2. 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

   [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.

               Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time
               Communication (WebRTC): Media Transport and Use of RTP",
               draft-ietf-rtcweb-rtp-usage-05 (work in progress),
               October 2012.

14. 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

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   this from Paolo Severini, Jim Hasselbrook, Joe Marcus, and Erik

   This document was prepared using

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Appendix A.                 Code Hints

   On windows setting the source interface works but BSD, OSX, Linux use
   weak end-system model and will route out different interface if that
   looks like a better route.  (TODO - Can someone verify this with
   specific versions?)

   In windows you might be able to tell something about priority of an
   interface for ICE purposes with WlanQueryInterface or GetIfTable.

   The specific mechanisms required to set DSCP code points depend on
   the application platform.

   In windows, setting the DSCP is not easy.  See Knowledge Base Article
   KB248611.  TODO - add more information about what can be done for

   For most Unix variants, the following program can set DSCP.

   TODO - make this work in V6.  For v6 have a look at IPv6_TCLASS or
   better the tclass part of sin6_flowid for IPv6

   TODO - Can someone test and report back results of program in iOS,
   Android, Linux, OSX, BSD.

   Example test program:

   #include <sys/types.h>
   #include <sys/socket.h>
   #include <netdb.h>
   #include <netinet/in.h>
   #include <arpa/inet.h>
   #include <stdio.h>
   #include <string.h>
   #include <stdlib.h>
   #include <errno.h>
   #include <unistd.h>

   #define MSG "Hello, World!"

   int main(void) {
       int sock = -1;
       struct sockaddr *local_addr = NULL;
       struct sockaddr_in sockin, host;
       int tos = 0x60; /* CS3 */
       socklen_t socksiz = 0;
       char *buffer = NULL;
       sock = socket(AF_INET, SOCK_DGRAM, 0);
       if (sock < 0) {

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           fprintf(stderr,"Error: %s\n", strerror(errno));
       memset(&sockin, 0, sizeof(sockin));
       sockin.sin_family = PF_INET;
       sockin.sin_addr.s_addr = inet_addr("");
       socksiz = sizeof(sockin);

       local_addr = (struct sockaddr *) &sockin;

       /* Set ToS/DSCP */
       if (setsockopt(sock, IPPROTO_IP, IP_TOS,  &tos,
                      sizeof(tos)) < 0) {
          fprintf(stderr,"Error setting TOS: %s\n", strerror(errno));

       /* Bind to a specific local address */
       if (bind(sock, local_addr, socksiz) < 0) {
                  "Error binding to socket: %s\n", strerror(errno));
          close(sock); sock=-1;

       buffer = (char *) malloc(strlen(MSG) + 1);
       if ( buffer == NULL ) {
                   "Error allocating memory: %s\n", strerror(errno));
           close( sock ); sock=-1;
       strlcpy(buffer, MSG, strlen(MSG) + 1);
       memset(&host, 0, sizeof(host));
       host.sin_family = PF_INET;
       host.sin_addr.s_addr = inet_addr("");
       host.sin_port = htons(12345);

       if (sendto(sock, buffer, strlen(buffer), 0,
                  (struct sockaddr *) &host, sizeof(host)) < 0) {
                   "Error sending message: %s\n", strerror(errno));
           close(sock); sock=-1;
           free(buffer); buffer=NULL;


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       return 0;

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Authors' Addresses

   Subha Dhesikan
   Cisco Systems, Inc.
   170 W Tasman St
   San Jose, CA 95134


   Dan Druta


   Paul E. Jones
   Cisco Systems, Inc.
   7025 Kit Creek Rd
   Research Triangle Park, NC 27709


   James Polk
   Cisco Systems, Inc.
   3913 Treemont Circle
   Colleyville, Texas 75082


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