draft-ietf-tsvwg-rtcweb-qos-07.txt   draft-ietf-tsvwg-rtcweb-qos-08.txt 
Network Working Group S. Dhesikan Network Working Group S. Dhesikan
Internet-Draft C. Jennings Internet-Draft C. Jennings
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: June 20, 2016 D. Druta, Ed. Expires: July 25, 2016 D. Druta, Ed.
AT&T AT&T
P. Jones P. Jones
Cisco Systems Cisco Systems
December 18, 2015 January 22, 2016
DSCP and other packet markings for WebRTC QoS DSCP and other packet markings for WebRTC QoS
draft-ietf-tsvwg-rtcweb-qos-07 draft-ietf-tsvwg-rtcweb-qos-08
Abstract Abstract
Many networks, such as service provider and enterprise networks, can Many networks, such as service provider and enterprise networks, can
provide treatment for individual packets based on Differentiated provide treatment for individual packets based on Differentiated
Services Code Point (DSCP) values on a per-hop basis. This document Services Code Point (DSCP) values on a per-hop basis. This document
provides the recommended DSCP values for browsers to use for various provides the recommended DSCP values for web browsers to use for
classes of traffic. various classes of WebRTC traffic.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 20, 2016. This Internet-Draft will expire on July 25, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 20 skipping to change at page 2, line 20
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Relation to Other Standards . . . . . . . . . . . . . . . . . 3 2. Relation to Other Standards . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5 5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Downward References . . . . . . . . . . . . . . . . . . . . . 7 8. Downward References . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Dedication . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. Dedication . . . . . . . . . . . . . . . . . . . . . . . . . 7
11. Document History . . . . . . . . . . . . . . . . . . . . . . 8 11. Document History . . . . . . . . . . . . . . . . . . . . . . 8
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
12.1. Normative References . . . . . . . . . . . . . . . . . . 8 12.1. Normative References . . . . . . . . . . . . . . . . . . 8
12.2. Informative References . . . . . . . . . . . . . . . . . 9 12.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
Differentiated Services Code Points (DSCP) [RFC2474] style packet Differentiated Services Code Points (DSCP) [RFC2474] packet marking
marking can help provide QoS in some environments. There are many can help provide QoS in some environments. This specification
use cases where such marking does not help, but it seldom makes proposes how WebRTC applications can mark packets, but does not
things worse if packets are marked appropriately. In other words, if contradict or redefine any advice from previous IETF RFCs. Rather,
too many packets, say all audio or all audio and video, are marked it merely provides a simple set of recommendations for implementers
for a given network condition then it can prevent desirable results. based on the previous RFCs.
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 specification proposes how WebRTC applications can mark packets. There are many use cases where such marking does not help, but it
This specification does not contradict or redefine any advice from seldom makes things worse if packets are marked appropriately. As
previous IETF RFCs, but merely provides a simple set of one example of where it does not help, if too many packets, say all
recommendations for implementers based on the previous RFCs 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).
There are some environments where DSCP markings frequently help. There are some environments where DSCP markings frequently help.
These include: These include:
1. Private, wide-area networks. 1. Private, wide-area networks.
2. Residential Networks. If the congested link is the broadband 2. Residential Networks. If the congested link is the broadband
uplink in a cable or DSL scenario, often residential routers/NAT uplink in a cable or DSL scenario, often residential routers/NAT
support preferential treatment based on DSCP. support preferential treatment based on DSCP.
skipping to change at page 3, line 22 skipping to change at page 3, line 22
them to something when there is no site specific information. In them to something when there is no site specific information. In
this document, "browsers" is used synonymously with "Interactive User this document, "browsers" is used synonymously with "Interactive User
Agent" as defined in the HTML specification, Agent" as defined in the HTML specification,
[W3C.REC-html5-20141028]. This document describes a subset of DSCP [W3C.REC-html5-20141028]. This document describes a subset of DSCP
code point values drawn from existing RFCs and common usage for use code point values drawn from existing RFCs and common usage for use
with WebRTC applications. These code points are solely defaults. with WebRTC applications. These code points are solely defaults.
This specification defines some inputs that the browser in a WebRTC This specification defines some inputs that the browser in a WebRTC
application can consider to aid in determining how to set the various application can consider to aid in determining how to set the various
packet markings and defines the mapping from abstract QoS policies packet markings and defines the mapping from abstract QoS policies
(data type, priority level) to those packet markings. (flow type, priority level) to those packet markings.
2. Relation to Other Standards 2. Relation to Other Standards
This document exists as a complement to [I-D.ietf-dart-dscp-rtp], This document exists as a complement to [I-D.ietf-dart-dscp-rtp],
which describes the interaction between DSCP and real-time which describes the interaction between DSCP and real-time
communications. It covers the implications of using various DSCP communications. It covers the implications of using various DSCP
values, particularly focusing on Real-time Transport Protocol (RTP) values, particularly focusing on Real-time Transport Protocol (RTP)
[RFC3550] streams that are multiplexed onto a single transport-layer [RFC3550] streams that are multiplexed onto a single transport-layer
flow. flow.
skipping to change at page 4, line 22 skipping to change at page 4, line 22
benefits the first few hops. benefits the first few hops.
3. Terminology 3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
4. Inputs 4. Inputs
The below uses the concept of a media flow, however this is usually WebRTC entities transmit and receive two types of media of
not equivalent to a transport-layer flow defined by a 5-tuple (source significance to this document: RTP streams
address, destination address, source port, destination port, and [I-D.ietf-rtcweb-rtp-usage] and data channels
protocol). Instead each media flow, such as an RTP stream [I-D.ietf-rtcweb-data-channel]. Each of the RTP streams and distinct
[I-D.ietf-rtcweb-rtp-usage] or SCTP association carrying data channel data channels consists of all of the packets associated with an
packets [I-D.ietf-rtcweb-data-channel], contains all the packets independent media entity and are not alway equivalent to a transport-
associated with an independent media entity within one 5-tuple. layer flow defined by a 5-tuple (source address, destination address,
There may be multiple media flows within the same 5-tuple. These source port, destination port, and protocol). There may be multiple
media flows might consist of different media types and have different RTP streams and data channels multiplexed over the same 5-tuple, with
levels of importance to the application and, therefore, each each having a different level of importance to the application and,
potentially marked using different DSCP values than for another media therefore, potentially marked using different DSCP values than
flow multiplexed over the same transport-layer flow. The following another RTP stream or data channel within the same transport-layer
are the inputs that the browser provides to the media engine: flow. (Note that there are restrictions with respect to marking
different data channels carried within the same SCTP association as
outlined in Section 5.)
o Data Type: The browser provides this input as it knows if the flow The following are the inputs that the browser provides to the media
engine:
o Flow Type: The browser provides this input as it knows if the flow
is audio, interactive video with or without audio, non-interactive is audio, interactive video with or without audio, non-interactive
video with or without audio, or data. video with or without audio, or data.
o Application Priority: Another input is the relative importance of o Application Priority: Another input is the relative importance of
the flow within that data type. Many applications have multiple an RTP stream or data channel flow. Many applications have
media flows of the same data type and often some flows are more multiple flows of the same Flow Type and often some flows are more
important than others. For example, in a video conference where important than others. For example, in a video conference where
there are usually audio and video flows, the audio flow may be there are usually audio and video flows, the audio flow may be
more important than the video flow. JavaScript applications can more important than the video flow. JavaScript applications can
tell the browser whether a particular media flow is high, medium, tell the browser whether a particular flow is high, medium, low or
low or very low importance to the application. very low importance to the application.
[I-D.ietf-rtcweb-transports] defines in more detail what an [I-D.ietf-rtcweb-transports] defines in more detail what an
individual media flow is within the WebRTC context. individual flow is within the WebRTC context.
As an example of different media flows that might be multiplexed over
the same transport-layer flow, packets related to one RTP stream
(e.g., an audio flow) carried over UDP might be one media flow,
packets related to a second RTP stream (e.g., presentation video)
carried over UDP might be a second media flow, and finally data
channel packets carried via SCTP over DTLS might be third media flow.
5. DSCP Mappings 5. DSCP Mappings
Below is a table of DSCP markings for each data type of interest to The DSCP markings for each flow type of interest to WebRTC given the
WebRTC. These DSCP values for each data type listed are a reasonable application priority is shown in the following table. The DSCP
subset of code point values taken from [RFC4594]. A web browser values for each flow type listed are a reasonable subset of code
SHOULD use these values to mark the appropriate media packets. More point values taken from [RFC4594]. A web browser SHOULD use these
information on EF can be found in [RFC3246]. More information on AF values to mark the appropriate media packets. More information on EF
can be found in [RFC2597]. DF is default forwarding which provides can be found in [RFC3246]. More information on AF can be found in
the basic best effort service. [RFC2597]. DF is default forwarding which provides the basic best
effort service.
+------------------------+-------+------+-------------+-------------+ +------------------------+-------+------+-------------+-------------+
| Data Type | Very | Low | Medium | High | | Flow Type | Very | Low | Medium | High |
| | Low | | | | | | Low | | | |
+------------------------+-------+------+-------------+-------------+ +------------------------+-------+------+-------------+-------------+
| Audio | CS1 | DF | EF (46) | EF (46) | | Audio | CS1 | DF | EF (46) | EF (46) |
| | (8) | (0) | | | | | (8) | (0) | | |
| | | | | | | | | | | |
| Interactive Video with | CS1 | DF | AF42, AF43 | AF41, AF42 | | Interactive Video with | CS1 | DF | AF42, AF43 | AF41, AF42 |
| or without audio | (8) | (0) | (36, 38) | (34, 36) | | or without audio | (8) | (0) | (36, 38) | (34, 36) |
| | | | | | | | | | | |
| Non-Interactive Video | CS1 | DF | AF32, AF33 | AF31, AF32 | | Non-Interactive Video | CS1 | DF | AF32, AF33 | AF31, AF32 |
| with or without audio | (8) | (0) | (28, 30) | (26, 28) | | with or without audio | (8) | (0) | (28, 30) | (26, 28) |
| | | | | | | | | | | |
| Data | CS1 | DF | AF11 | AF21 | | Data | CS1 | DF | AF11 | AF21 |
| | (8) | (0) | | | | | (8) | (0) | | |
+------------------------+-------+------+-------------+-------------+ +------------------------+-------+------+-------------+-------------+
Table 1: Recommended DSCP Values for WebRTC Applications Table 1: Recommended DSCP Values for WebRTC Applications
The columns "very low", "low", "Medium" and "high" signify the The application priority, indicated by the columns "very low", "low",
relative importance of the media flow within the application and is "Medium", and "high", signifies the relative importance of the flow
an input that the browser receives to assist it in selecting the DSCP within the application. It is an input that the browser receives to
value. These are referred to as application priority in this assist it in selecting the DSCP value. Application priority does not
document. Application priority does not refer to priority in the refer to priority in the network transport.
network transport.
The above table assumes that packets marked with CS1 are treated as The above table assumes that packets marked with CS1 are treated as
"less than best effort". However, the treatment of CS1 is "less than best effort". However, the treatment of CS1 is
implementation dependent. If an implementation treats CS1 as other implementation dependent. If an implementation treats CS1 as other
than "less than best effort", then the actual priority (or, more than "less than best effort", then the actual priority (or, more
precisely, the per-hop-behavior) of the packets may be changed from precisely, the per-hop-behavior) of the packets may be changed from
what is intended. It is common for CS1 to be treated the same as DF what is intended. It is common for CS1 to be treated the same as DF,
so anyone using CS1 cannot assume that CS1 will be treated so anyone using CS1 cannot assume that CS1 will be treated
differently than DF. Implementers should also note that the excess differently than DF. Implementers should also note that excess EF
EF traffic is dropped. This could mean that a packet marked as EF traffic is dropped. This could mean that a packet marked as EF may
may not get through as opposed to a packet marked with a different not get through as opposed to a packet marked with a different DSCP
DSCP value. value.
The browser SHOULD first select the data type of the media flow.
Within the data type, the relative importance of the media flow
SHOULD be used to select the appropriate DSCP value.
The combination of data type and application priority provides The browser SHOULD first select the flow type of the flow. Within
specificity and helps in selecting the right DSCP value for the media the flow type, the relative importance of the flow SHOULD be used to
flow. In some cases, the different drop precedence values provides select the appropriate DSCP value.
additional granularity in classifying packets within a media flow.
For example, in a video conference, the video media flow may have
medium application 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.
All packets within a media flow SHOULD have the same application The combination of flow type and application priority provides
priority. In some cases, the selected cell may have multiple DSCP specificity and helps in selecting the right DSCP value for the flow.
values, such as AF41 and AF42. These offer different drop All packets within a flow SHOULD have the same application priority.
precedences. With the exception of data channel traffic, one may In some cases, the selected application priority cell may have
select different drop precedences for the different packets in the multiple DSCP values, such as AF41 and AF42. These offer different
same media flow. Therefore, all packets in the media flow SHOULD be drop precedences. The different drop precedence values provides
marked with the same application priority, but can have different additional granularity in classifying packets within a flow. For
drop precedences. example, in a video conference, the video flow may have medium
application 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.
For reasons discussed in Section 6 of [I-D.ietf-dart-dscp-rtp], if For reasons discussed in Section 6 of [I-D.ietf-dart-dscp-rtp], if
multiple media flows are multiplexed using a reliable transport multiple flows are multiplexed using a reliable transport (e.g., TCP)
(e.g., TCP) then all of the packets for all media flows multiplexed then all of the packets for all flows multiplexed over that
over that transport-layer flow MUST be marked using the same DSCP transport-layer flow MUST be marked using the same DSCP value.
value. Likewise, all WebRTC data channel packets transmitted over an Likewise, all WebRTC data channel packets transmitted over an SCTP
SCTP association MUST be marked using the same DSCP value, regardless association MUST be marked using the same DSCP value, regardless of
of how many data channels (streams) exist or what kind of traffic is how many data channels (streams) exist or what kind of traffic is
carried over the various SCTP streams. In the event that the browser carried over the various SCTP streams. In the event that the browser
wishes to change the DSCP value in use for an SCTP association, it wishes to change the DSCP value in use for an SCTP association, it
MUST reset the SCTP congestion controller after changing values. MUST reset the SCTP congestion controller after changing values.
Frequent changes in the DSCP value used for an SCTP association are Frequent changes in the DSCP value used for an SCTP association are
discouraged, though, as this would defeat any attempts at effectively discouraged, though, as this would defeat any attempts at effectively
managing congestion. It should also be noted that any change in DSCP managing congestion. It should also be noted that any change in DSCP
value that results in a reset of the congestion controller puts the value that results in a reset of the congestion controller puts the
SCTP association back into slow start, which may have undesirable SCTP association back into slow start, which may have undesirable
effects on application performance. effects on application performance.
For the data channel traffic multiplexed over an SCTP association, it For the data channel traffic multiplexed over an SCTP association, it
is RECOMMENDED that the DSCP value selected be the one associated is RECOMMENDED that the DSCP value selected be the one associated
with the highest priority requested for all data channels multiplexed with the highest priority requested for all data channels multiplexed
over the SCTP association. Likewise, when multiplexing multiple over the SCTP association. Likewise, when multiplexing multiple
media flows over a TCP connection, the DCSP value selected should be flows over a TCP connection, the DCSP value selected should be the
the one associated with the highest priority requested for all one associated with the highest priority requested for all
multiplexed flows. multiplexed flows.
If a packet enters a QoS domain that has no support for the above If a packet enters a QoS domain that has no support for the above
defined data types/application priority (service class), then the defined flow types/application priority (service class), then the
network node at the edge will remark the DSCP value based on network node at the edge will remark the DSCP value based on
policies. This could result in the media flow not getting the policies. This could result in the flow not getting the network
network treatment it expects based on the original DSCP value in the treatment it expects based on the original DSCP value in the packet.
packet. Subsequently, if the packet enters a QoS domain that Subsequently, if the packet enters a QoS domain that supports a
supports a larger number of service classes, there may not be larger number of service classes, there may not be sufficient
sufficient information in the packet to restore the original information in the packet to restore the original markings.
markings. Mechanisms for restoring such original DSCP is outside the Mechanisms for restoring such original DSCP is outside the scope of
scope of this document. this document.
In summary, there are no guarantees or promised level of service with In summary, there are no guarantees or promised level of service with
the use of DSCP. The service provided to a packet is dependent upon the use of DSCP. The service provided to a packet is dependent upon
the network design along the path, as well as the congestion levels the network design along the path, as well as the congestion levels
at every hop. at every hop.
6. Security Considerations 6. Security Considerations
This specification does not add any additional security implication This specification does not add any additional security implication
other than the normal application use of DSCP. For security other than the normal application use of DSCP. For security
implications on use of DSCP, please refer to Section 6 of RFC 4594. implications on use of DSCP, please refer to Section 6 of [RFC4594].
Please also see [I-D.ietf-rtcweb-security] as an additional Please also see [I-D.ietf-rtcweb-security] as an additional
reference. reference.
7. IANA Considerations 7. IANA Considerations
This specification does not require any actions from IANA. This specification does not require any actions from IANA.
8. Downward References 8. Downward References
This specification contains a downwards reference to [RFC4594]. This specification contains a downwards reference to [RFC4594].
However, the parts of that RFC used by this specification are However, the parts of that RFC used by this specification are
sufficiently stable for this downward reference. sufficiently stable for this downward reference.
9. Acknowledgements 9. Acknowledgements
Thanks To David Black, Magnus Westerland, Paolo Severini, Jim Thanks To David Black, Magnus Westerland, Paolo Severini, Jim
Hasselbrook, Joe Marcus, Erik Nordmark, and Michael Tuexen for their Hasselbrook, Joe Marcus, Erik Nordmark, and Michael Tuexen for their
help. invaluable input.
10. Dedication 10. Dedication
This document is dedicated to the memory of James Polk, a long-time This document is dedicated to the memory of James Polk, a long-time
friend and colleague. James made important contributions to this friend and colleague. James made important contributions to this
specification, including being one of its primary authors. The IETF specification, including being one of its primary authors. The IETF
global community mourns his loss and he will be missed dearly. global community mourns his loss and he will be missed dearly.
11. Document History 11. Document History
Note to RFC Editor: Please remove this section. Note to RFC Editor: Please remove this section.
This document was originally an individual submission in RTCWeb WG. This document was originally an individual submission in RTCWeb WG.
The RTCWeb working group selected it to be become a WG document. 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 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 as that seemed to be a better match.
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.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-dart-dscp-rtp] [I-D.ietf-dart-dscp-rtp]
Black, D. and P. Jones, "Differentiated Services Black, D. and P. Jones, "Differentiated Services
(DiffServ) and Real-time Communication", draft-ietf-dart- (DiffServ) and Real-time Communication", draft-ietf-dart-
dscp-rtp-10 (work in progress), November 2014. dscp-rtp-10 (work in progress), November 2014.
skipping to change at page 8, line 52 skipping to change at page 8, line 43
[I-D.ietf-rtcweb-security] [I-D.ietf-rtcweb-security]
Rescorla, E., "Security Considerations for WebRTC", draft- Rescorla, E., "Security Considerations for WebRTC", draft-
ietf-rtcweb-security-08 (work in progress), February 2015. ietf-rtcweb-security-08 (work in progress), February 2015.
[I-D.ietf-rtcweb-transports] [I-D.ietf-rtcweb-transports]
Alvestrand, H., "Transports for WebRTC", draft-ietf- Alvestrand, H., "Transports for WebRTC", draft-ietf-
rtcweb-transports-10 (work in progress), October 2015. rtcweb-transports-10 (work in progress), October 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594, August Guidelines for DiffServ Service Classes", RFC 4594, DOI
2006. 10.17487/RFC4594, August 2006,
<http://www.rfc-editor.org/info/rfc4594>.
12.2. Informative References 12.2. Informative References
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, December Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI
1998. 10.17487/RFC2474, December 1998,
<http://www.rfc-editor.org/info/rfc2474>.
[RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
"Assured Forwarding PHB Group", RFC 2597, June 1999. "Assured Forwarding PHB Group", RFC 2597, DOI 10.17487/
RFC2597, June 1999,
<http://www.rfc-editor.org/info/rfc2597>.
[RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
J., Courtney, W., Davari, S., Firoiu, V., and D. J., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, March 2002. Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<http://www.rfc-editor.org/info/rfc3246>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>. July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[W3C.REC-html5-20141028] [W3C.REC-html5-20141028]
Hickson, I., Berjon, R., Faulkner, S., Leithead, T., Hickson, I., Berjon, R., Faulkner, S., Leithead, T.,
Navara, E., O&#039;Connor, E., and S. Pfeiffer, "HTML5", Navara, E., O&#039;Connor, E., and S. Pfeiffer, "HTML5",
World Wide Web Consortium Recommendation REC- World Wide Web Consortium Recommendation REC-
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