draft-ietf-tsvwg-rtcweb-qos-05.txt   draft-ietf-tsvwg-rtcweb-qos-06.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: April 18, 2016 D. Druta, Ed. Expires: June 20, 2016 D. Druta, Ed.
AT&T AT&T
P. Jones P. Jones
Cisco Systems Cisco Systems
October 16, 2015 December 18, 2015
DSCP and other packet markings for WebRTC QoS DSCP and other packet markings for WebRTC QoS
draft-ietf-tsvwg-rtcweb-qos-05 draft-ietf-tsvwg-rtcweb-qos-06
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 browsers to use for various
classes of traffic. classes of traffic.
Status of This Memo Status of This Memo
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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 April 18, 2016. This Internet-Draft will expire on June 20, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 7 10. Dedication . . . . . . . . . . . . . . . . . . . . . . . . . 8
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 . . . . . . . . . . . . . . . . . 8 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] style packet
marking can help provide QoS in some environments. There are many marking can help provide QoS in some environments. There are many
use cases where such marking does not help, but it seldom makes use cases where such marking does not help, but it seldom makes
things worse if packets are marked appropriately. In other words, if things worse if packets are marked appropriately. In other words, if
too many packets, say all audio or all audio and video, are marked too many packets, say all audio or all audio and video, are marked
for a given network condition then it can prevent desirable results. for a given network condition then it can prevent desirable results.
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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.
3. Wireless Networks. If the congested link is a local wireless 3. Wireless Networks. If the congested link is a local wireless
network, marking may help. network, marking may help.
Traditionally DSCP values have been thought of as being site Traditionally DSCP values have been thought of as being site
specific, with each site selecting its own code points for specific, with each site selecting its own code points for
controlling per-hop-behavior to influence the QoS for transport controlling per-hop-behavior to influence the QoS for transport-layer
flows. However in the WebRTC use cases, the browsers need to set flows. However in the WebRTC use cases, the browsers need to set
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
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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.
There are a number of guidelines specified in There are a number of guidelines specified in
[I-D.ietf-dart-dscp-rtp] that should be followed when marking traffic [I-D.ietf-dart-dscp-rtp] that should be followed when marking traffic
sent by WebRTC applications, as it is common for multiple RTP streams sent by WebRTC applications, as it is common for multiple RTP streams
to be multiplexed on the same transport flow. Generally, the RTP to be multiplexed on the same transport-layer flow. Generally, the
streams would be marked with a value as appropriate from Table 1. A RTP streams would be marked with a value as appropriate from Table 1.
WebRTC application might also multiplex data channel A WebRTC application might also multiplex data channel
[I-D.ietf-rtcweb-data-channel] traffic over the same 5-tuple as RTP [I-D.ietf-rtcweb-data-channel] traffic over the same 5-tuple as RTP
streams, which would also be marked as per that table. The guidance streams, which would also be marked as per that table. The guidance
in [I-D.ietf-dart-dscp-rtp] says that all data channel traffic would in [I-D.ietf-dart-dscp-rtp] says that all data channel traffic would
be marked with a single value that is typically different than the be marked with a single value that is typically different than the
value(s) used for RTP streams multiplexed with the data channel value(s) used for RTP streams multiplexed with the data channel
traffic over the same 5-tuple, assuming RTP streams are marked with a traffic over the same 5-tuple, assuming RTP streams are marked with a
value other than default forwarding (DF). This is expanded upon value other than default forwarding (DF). This is expanded upon
further in the next section. further in the next section.
This specification does not change or override the advice in any This specification does not change or override the advice in any
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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 The below uses the concept of a media flow, however this is usually
not equivalent to a transport flow defined by a 5-tuple (source not equivalent to a transport-layer flow defined by a 5-tuple (source
address, destination address, source port, destination port, and address, destination address, source port, destination port, and
protocol). Instead each media flow contains all the packets protocol). Instead each media flow, such as an RTP stream
[I-D.ietf-rtcweb-rtp-usage] or SCTP association carrying data channel
packets [I-D.ietf-rtcweb-data-channel], contains all the packets
associated with an independent media entity within one 5-tuple. associated with an independent media entity within one 5-tuple.
There may be multiple media flows within the same 5-tuple. These Specifically, a media flow is the transmitted packets for an RTP
media flows might consist of different media types and have different session or an SCTP association. There may be multiple media flows
levels of importance to the application and, therefore, each within the same 5-tuple. These media flows might consist of
potentially marked using different DSCP values than for another media different media types and have different levels of importance to the
flow multiplexed over the same transport flow. The following are the application and, therefore, each potentially marked using different
inputs that the browser provides to the media engine: DSCP values than for another media flow multiplexed over the same
transport-layer flow. 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 o Data 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 the flow within that data type. Many applications have multiple
media flows of the same data type and often some flows are more media flows of the same data 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 media flow is high, medium,
low or very low importance to the application. low or 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 media flow is within the WebRTC context.
As an example of different media flows that might be multiplexed over As an example of different media flows that might be multiplexed over
the same transport flow, packets related to one RTP stream (e.g., an the same transport-layer flow, packets related to one RTP stream
audio flow) carried over UDP might be one media flow, packets related (e.g., an audio flow) carried over UDP might be one media flow,
to a second RTP stream (e.g., presentation video) carried over UDP packets related to a second RTP stream (e.g., presentation video)
might be a second media flow, and finally data channel packets carried over UDP might be a second media flow, and finally data
carried via SCTP over DTLS might be third media flow. 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 Below is a table of DSCP markings for each data type of interest to
WebRTC. These DSCP values for each data type listed are a reasonable WebRTC. These DSCP values for each data type listed are a reasonable
subset of code point values taken from [RFC4594]. A web browser subset of code point values taken from [RFC4594]. A web browser
SHOULD use these values to mark the appropriate media packets. More SHOULD use these values to mark the appropriate media packets. More
information on EF can be found in [RFC3246]. More information on AF information on EF can be found in [RFC3246]. More information on AF
can be found in [RFC2597]. DF is default forwarding which provides can be found in [RFC2597]. DF is default forwarding which provides
the basic best effort service. the basic best effort service.
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values, such as AF41 and AF42. These offer different drop values, such as AF41 and AF42. These offer different drop
precedences. With the exception of data channel traffic, one may precedences. With the exception of data channel traffic, one may
select different drop precedences for the different packets in the select different drop precedences for the different packets in the
same media flow. Therefore, all packets in the media flow SHOULD be same media flow. Therefore, all packets in the media flow SHOULD be
marked with the same application priority, but can have different marked with the same application priority, but can have different
drop precedences. drop precedences.
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 media flows are multiplexed using a reliable transport
(e.g., TCP) then all of the packets for all media flows multiplexed (e.g., TCP) then all of the packets for all media flows multiplexed
over that transport flow MUST be marked using the same DSCP value. over that transport-layer flow MUST be marked using the same DSCP
Likewise, all WebRTC data channel packets transmitted over an SCTP value. Likewise, all WebRTC data channel packets transmitted over an
association MUST be marked using the same DSCP value, regardless of SCTP association MUST be marked using the same DSCP value, regardless
how many data channels (streams) exist or what kind of traffic is of 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.
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[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.
[I-D.ietf-rtcweb-data-channel] [I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-13 (work in Channels", draft-ietf-rtcweb-data-channel-13 (work in
progress), January 2015. progress), January 2015.
[I-D.ietf-rtcweb-rtp-usage]
Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time
Communication (WebRTC): Media Transport and Use of RTP",
draft-ietf-rtcweb-rtp-usage-25 (work in progress), June
2015.
[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-09 (work in progress), July 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, March 1997.
[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, August
2006. 2006.
12.2. Informative References 12.2. Informative References
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