One document matched: draft-ietf-tsvwg-rtcweb-qos-03.xml
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<rfc category="std" docName="draft-ietf-tsvwg-rtcweb-qos-03"
ipr="trust200902">
<front>
<title abbrev="RTCWeb QoS">DSCP and other packet markings for RTCWeb
QoS</title>
<author fullname="Subha Dhesikan" initials="S." surname="Dhesikan">
<organization>Cisco Systems</organization>
<address>
<email>sdhesika@cisco.com</email>
</address>
</author>
<author fullname="Cullen Jennings" initials="C."
surname="Jennings">
<organization>Cisco Systems</organization>
<address>
<email>fluffy@cisco.com</email>
</address>
</author>
<author fullname="Dan Druta" initials="D." role="editor" surname="Druta">
<organization>AT&T</organization>
<address>
<email>dd5826@att.com</email>
</address>
</author>
<author fullname="Paul E. Jones" initials="P." surname="Jones">
<organization>Cisco Systems</organization>
<address>
<email>paulej@packetizer.com</email>
</address>
</author>
<author fullname="James Polk" initials="J." surname="Polk">
<organization>Cisco Systems</organization>
<address>
<email>jmpolk@cisco.com</email>
</address>
</author>
<date day="12" month="November" year="2014" />
<abstract>
<t>Many networks, such as service provider and enterprise networks, can
provide treatment for individual packets 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.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>
Differentiated Services Code Points (DSCP) <xref target="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).
</t>
<t>
This specification proposes how WebRTC applications can mark
packets. This specification 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.
</t>
<t>
There are some environments where priority markings frequently help.
These include:
</t>
<t>
1. Private, wide-area networks.
</t>
<t>
2. Residential Networks. If the congested link is the broadband
uplink in a cable or DSL scenario, often residential routers/NAT
support preferential treatment based on DSCP.
</t>
<t>
3. Wireless Networks. If the congested link is a local wireless
network, marking may help.
</t>
<t>
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. In
this document, "browsers" is used synonmously with "interactive User
Agent" as defined in the HTML specification, [W3C.WD-html-20110525].
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.
</t>
<t>
This specification 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.
</t>
</section>
<section title="Relation to Other Standards">
<t>
This document exists as a complement to <xref
target="I-D.ietf-dart-dscp-rtp" />, which describes the interaction
between DSCP and real-time communications. It covers the
implications of using various DSCP values, particularly focusing on
Real-time Transport Protocol (RTP) <xref target="RFC3550"/> streams
that are multiplexed onto a single transport-layer flow.
</t>
<t>
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 in the
RTCWeb context. In some cases, such as DSCP where the normative RFC
leaves open multiple options from which to choose, 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. </t> <t> The DSCP value set by the endpoint is
not always trusted by the network. Therefore, the DSCP value may be
remarked at any place in the network for a variety of reasons to any
other DSCP value, including default forwarding (DF) which provides
basic best effort service. The mitigation for such action is through
an authorization mechanism. Such authorization mechanism is outside
the scope of this document.
</t> </section>
<section title="Terminology">
<t>
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
in this document are to be interpreted as described in <xref
target="RFC2119" />.
</t>
</section>
<section title="Inputs">
<t>
The below uses the concept of a media flow, however this is usually
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 consist of different media types and have
different priorities. The following are the inputs that the browser
provides to the media engine:
<list style="symbols">
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
<t>
[I-D.ietf-rtcweb-transports] defines in more detail what an
individual media flow is within the WebRTC context.
</t>
</section>
<section title="DSCP Mappings">
<t>
Below is a table of DSCP markings for each data type of interest to
RTCWeb. These DSCP values for each data type listed are a reasonable
default set of code point values taken from <xref target="RFC4594"
/>. A web browser SHOULD use these values to mark the appropriate
media packets. More information on EF can be found in <xref
target="RFC3246"/>. More information on AF can be found in <xref
target="RFC2597"/>. DF is default forwarding which provides the
basic best effort service. The mitigation for such action is through
an authorization mechanism. Such authorization mechanism is outside
the scope of this document.
</t>
<texttable anchor="table-dscp">
<ttcol align="center">Data Type</ttcol>
<ttcol align="center">Very Low</ttcol>
<ttcol align="center">Low</ttcol>
<ttcol align="center">Medium</ttcol>
<ttcol align="center">High</ttcol>
<c>Audio</c>
<c>CS1 (8)</c>
<c>DF (0)</c>
<c>EF (46)</c>
<c>EF (46)</c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c>Interactive Video with or without audio</c>
<c>CS1 (8)</c>
<c>DF (0)</c>
<c>AF42, AF43 (36, 38)</c>
<c>AF41, AF42 (34, 36)</c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c>Non-Interactive Video with or without audio</c>
<c>CS1 (8)</c>
<c>DF (0)</c>
<c>AF32, AF33 (28, 30)</c>
<c>AF31, AF32 (26, 28)</c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c> </c>
<c>Data</c>
<c>CS1 (8)</c>
<c>DF (0)</c>
<c>AF1x (10, 12, 14)</c>
<c>AF2x (18, 20, 22)</c>
</texttable>
<t>
The columns "very low", "low", "Medium" and "high" are the priority
levels. This priority value signifies the relative priority of the
media flow within the application and is provided to the browser to
assist it in selecting the DSCP value. The browser 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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
If a packet enters a QoS domain that has no support for the above
defined Data Types/Application (service) 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.
</t>
</section>
<section title="Security Considerations">
<t>
This specification 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 <xref target="I-D.ietf-rtcweb-security" /> as an
additional reference.
</t>
</section>
<section title="IANA Considerations">
<t>This specification does not require any actions from IANA.</t>
</section>
<section title="Downward References">
<t>This specification contains a downwards reference to <xref
target="RFC4594"/>. However, the parts of that RFC used by this
specification are sufficiently stable for this downward reference.</t>
</section>
<section title="Acknowledgements">
<t>
Thanks To David Black, Magnus Westerland, Paolo Severini, Jim
Hasselbrook, Joe Marcus, and Erik Nordmark for their help.
</t>
</section>
<section title="Document History">
<t>Note to RFC Editor: Please remove this section.</t>
<t>
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.
</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="RFC4594">
<front>
<title>Configuration Guidelines for DiffServ Service Classes</title>
<author fullname="J. Babiarz" initials="J." surname="Babiarz">
<organization></organization>
</author>
<author fullname="K. Chan" initials="K." surname="Chan">
<organization></organization>
</author>
<author fullname="F. Baker" initials="F." surname="Baker">
<organization></organization>
</author>
<date month="August" year="2006" />
</front>
<seriesInfo name="RFC" value="4594" />
<format octets="144044"
target="http://www.rfc-editor.org/rfc/rfc4594.txt" type="TXT" />
</reference>
<reference anchor="RFC2119">
<front>
<title abbrev="RFC Key Words">Key words for use in RFCs to Indicate
Requirement Levels</title>
<author fullname="Scott Bradner" initials="S." surname="Bradner">
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street>
</postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email>
</address>
</author>
<date month="March" year="1997" />
<area>General</area>
<keyword>keyword</keyword>
</front>
<seriesInfo name="BCP" value="14" />
<seriesInfo name="RFC" value="2119" />
<format octets="4723"
target="http://www.rfc-editor.org/rfc/rfc2119.txt" type="TXT" />
<format octets="17491"
target="http://xml.resource.org/public/rfc/html/rfc2119.html"
type="HTML" />
<format octets="5777"
target="http://xml.resource.org/public/rfc/xml/rfc2119.xml"
type="XML" />
</reference>
<?rfc include='reference.I-D.ietf-dart-dscp-rtp'?>
<?rfc include='reference.I-D.ietf-rtcweb-security'?>
</references>
<references title="Informative References">
<reference anchor="RFC3246">
<front>
<title>An Expedited Forwarding PHB (Per-Hop Behavior)</title>
<author fullname="B. Davie" initials="B." surname="Davie">
<organization></organization>
</author>
<author fullname="A. Charny" initials="A." surname="Charny">
<organization></organization>
</author>
<author fullname="J.C.R. Bennet" initials="J.C.R." surname="Bennet">
<organization></organization>
</author>
<author fullname="K. Benson" initials="K." surname="Benson">
<organization></organization>
</author>
<author fullname="J.Y. Le Boudec" initials="J.Y."
surname="Le Boudec">
<organization></organization>
</author>
<author fullname="W. Courtney" initials="W." surname="Courtney">
<organization></organization>
</author>
<author fullname="S. Davari" initials="S." surname="Davari">
<organization></organization>
</author>
<author fullname="V. Firoiu" initials="V." surname="Firoiu">
<organization></organization>
</author>
<author fullname="D. Stiliadis" initials="D." surname="Stiliadis">
<organization></organization>
</author>
<date month="March" year="2002" />
</front>
<seriesInfo name="RFC" value="3246" />
<format octets="33896"
target="http://www.rfc-editor.org/rfc/rfc3246.txt" type="TXT" />
</reference>
<reference anchor="RFC2474">
<front>
<title abbrev="Differentiated Services Field">Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6
Headers</title>
<author fullname="Kathleen Nichols" initials="K." surname="Nichols">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>170 West Tasman Drive</street>
<city>San Jose</city>
<region>CA</region>
<code>95134-1706</code>
<country>USA</country>
</postal>
<phone>+1 408 525 4857</phone>
<email>kmn@cisco.com</email>
</address>
</author>
<author fullname="Steven Blake" initials="S." surname="Blake">
<organization>Torrent Networking Technologies</organization>
<address>
<postal>
<street>3000 Aerial Center</street>
<city>Morrisville</city>
<region>NC</region>
<code>27560</code>
<country>USA</country>
</postal>
<phone>+1 919 468 8466 x232</phone>
<email>slblake@torrentnet.com</email>
</address>
</author>
<author fullname="Fred Baker" initials="F." surname="Baker">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>519 Lado Drive</street>
<city>Santa Barbara</city>
<region>CA</region>
<code>93111</code>
<country>USA</country>
</postal>
<phone>+1 408 526 4257</phone>
<email>fred@cisco.com</email>
</address>
</author>
<author fullname="David L. Black" initials="D.L." surname="Black">
<organization>EMC Corporation</organization>
<address>
<postal>
<street>35 Parkwood Drive</street>
<city>Hopkinton</city>
<region>MA</region>
<code>01748</code>
<country>USA</country>
</postal>
<phone>+1 508 435 1000 x76140</phone>
<email>black_david@emc.com</email>
</address>
</author>
<date month="December" year="1998" />
<area>Internet</area>
<keyword>internet protocol version 4</keyword>
<keyword>IPv6</keyword>
<keyword>IPv4</keyword>
<keyword>internet protocol version 6</keyword>
<keyword>type of service</keyword>
</front>
<seriesInfo name="RFC" value="2474" />
<format octets="50576"
target="http://www.rfc-editor.org/rfc/rfc2474.txt" type="TXT" />
<format octets="67719"
target="http://xml.resource.org/public/rfc/html/rfc2474.html"
type="HTML" />
<format octets="62259"
target="http://xml.resource.org/public/rfc/xml/rfc2474.xml"
type="XML" />
</reference>
<reference anchor="RFC2597">
<front>
<title>Assured Forwarding PHB Group</title>
<author fullname="Juha Heinanen" initials="J." surname="Heinanen">
<organization>Telia Finland</organization>
<address>
<postal>
<street>Myyrmaentie 2</street>
<city>Vantaa</city>
<code>01600</code>
<country>FI</country>
</postal>
<email>jh@telia.fi</email>
</address>
</author>
<author fullname="Fred Baker" initials="F." surname="Baker">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>519 Lado Drive</street>
<city>Santa Barbara</city>
<region>CA</region>
<code>93111</code>
<country>US</country>
</postal>
<email>fred@cisco.com</email>
</address>
</author>
<author fullname="Walter Weiss" initials="W." surname="Weiss">
<organization>Lucent Technologies</organization>
<address>
<postal>
<street>300 Baker Avenue</street>
<street>Suite 100</street>
<city>Concord</city>
<region>MA</region>
<code>01742-2168</code>
<country>US</country>
</postal>
<email>wweiss@lucent.com</email>
</address>
</author>
<author fullname="J. Wroclawski" initials="J." surname="Wroclawski">
<organization>MIT Laboratory for Computer Science</organization>
<address>
<postal>
<street>545 Technology Square</street>
<city>Cambridge</city>
<region>MA</region>
<code>02139</code>
<country>US</country>
</postal>
<email>jtw@lcs.mit.edu</email>
</address>
</author>
<date month="June" year="1999" />
</front>
<seriesInfo name="RFC" value="2597" />
<format octets="24068"
target="http://www.rfc-editor.org/rfc/rfc2597.txt" type="TXT" />
</reference>
<?rfc include='reference.RFC.3550'?>
</references>
</back>
</rfc>
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