draft-ietf-tsvwg-rtcweb-qos-18.txt   rfc8837.txt 
Network Working Group P. Jones Internet Engineering Task Force (IETF) P. Jones
Internet-Draft S. Dhesikan Request for Comments: 8837 Cisco Systems
Intended status: Standards Track C. Jennings Category: Standards Track S. Dhesikan
Expires: February 20, 2017 Cisco Systems ISSN: 2070-1721 Individual
C. Jennings
Cisco Systems
D. Druta D. Druta
AT&T AT&T
August 19, 2016 January 2021
DSCP Packet Markings for WebRTC QoS Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS
draft-ietf-tsvwg-rtcweb-qos-18
Abstract Abstract
Many networks, such as service provider and enterprise networks, can Networks can provide different forwarding treatments for individual
provide different forwarding treatments for individual packets based packets based on Differentiated Services Code Point (DSCP) values on
on Differentiated Services Code Point (DSCP) values on a per-hop a per-hop basis. This document provides the recommended DSCP values
basis. This document provides the recommended DSCP values for web for web browsers to use for various classes of Web Real-Time
browsers to use for various classes of WebRTC traffic. Communication (WebRTC) traffic.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on February 20, 2017. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8837.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2021 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 (https://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
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology
3. Relation to Other Specifications . . . . . . . . . . . . . . 3 3. Relation to Other Specifications
4. Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Inputs
5. DSCP Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5 5. DSCP Mappings
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations
8. Downward References . . . . . . . . . . . . . . . . . . . . . 9 8. Downward References
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 9. References
10. Dedication . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References
11. Document History . . . . . . . . . . . . . . . . . . . . . . 9 9.2. Informative References
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 Acknowledgements
12.1. Normative References . . . . . . . . . . . . . . . . . . 9 Dedication
12.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
Differentiated Services Code Point (DSCP) [RFC2474] packet marking Differentiated Services Code Point (DSCP) [RFC2474] packet marking
can help provide QoS in some environments. This specification can help provide QoS in some environments. This specification
provides default packet marking for browsers that support WebRTC provides default packet marking for browsers that support WebRTC
applications, but does not change any advice or requirements in other applications, but does not change any advice or requirements in other
IETF RFCs. The contents of this specification are intended to be a RFCs. The contents of this specification are intended to be a simple
simple set of implementation recommendations based on the previous set of implementation recommendations based on previous RFCs.
RFCs.
Networks where these DSCP markings are beneficial (likely to improve Networks in which these DSCP markings are beneficial (likely to
QoS for WebRTC traffic) include: improve QoS for WebRTC traffic) include:
1. Private, wide-area networks. Network administrators have control 1. Private, wide-area networks. Network administrators have control
over remarking packets and treatment of packets. over remarking packets and treatment of packets.
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, residential routers/NAT often
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.
There are cases where these DSCP markings do not help, but, aside There are cases where these DSCP markings do not help but, aside from
from possible priority inversion for "less than best effort traffic" possible priority inversion for "Less-than-Best-Effort traffic" (see
(see Section 5), they seldom make things worse if packets are marked Section 5), they seldom make things worse if packets are marked
appropriately. appropriately.
DSCP values are in principle site specific, with each site selecting DSCP values are, in principle, site specific with each site selecting
its own code points for controlling per-hop-behavior to influence the its own code points for controlling per-hop behavior to influence the
QoS for transport-layer flows. However in the WebRTC use cases, the QoS for transport-layer flows. However, in the WebRTC use cases, the
browsers need to set them to something when there is no site specific browsers need to set them to something when there is no site-specific
information. This document describes a subset of DSCP code point information. This document describes a subset of DSCP code point
values drawn from existing RFCs and common usage for use with WebRTC values drawn from existing RFCs and common usage for use with WebRTC
applications. These code points are intended to be the default applications. These code points are intended to be the default
values used by a WebRTC application. While other values could be values used by a WebRTC application. While other values could be
used, using a non-default value may result in unexpected per-hop used, using a non-default value may result in unexpected per-hop
behavior. It is RECOMMENDED that WebRTC applications use non-default behavior. It is RECOMMENDED that WebRTC applications use non-default
values only in private networks that are configured to use different values only in private networks that are configured to use different
values. values.
This specification defines inputs that are provided by the WebRTC This specification defines inputs that are provided by the WebRTC
application hosted in the browser that aid the browser in determining application hosted in the browser that aid the browser in determining
how to set the various packet markings. The specification also how to set the various packet markings. The specification also
defines the mapping from abstract QoS policies (flow type, priority defines the mapping from abstract QoS policies (flow type, priority
level) to those packet markings. level) to those packet markings.
2. Terminology 2. 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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The terms "browser" and "non-browser" are defined in [RFC7742] and The terms "browser" and "non-browser" are defined in [RFC7742] and
carry the same meaning in this document. carry the same meaning in this document.
3. Relation to Other Specifications 3. Relation to Other Specifications
This document is a complement to [RFC7657], which describes the This document is a complement to [RFC7657], which describes the
interaction between DSCP and real-time communications. That RFC interaction between DSCP and real-time communications. That RFC
covers the implications of using various DSCP values, particularly covers the implications of using various DSCP values, particularly
focusing on Real-time Transport Protocol (RTP) [RFC3550] streams that focusing on the Real-time Transport Protocol (RTP) [RFC3550] streams
are multiplexed onto a single transport-layer flow. that are multiplexed onto a single transport-layer flow.
There are a number of guidelines specified in [RFC7657] that apply to There are a number of guidelines specified in [RFC7657] that apply to
marking traffic sent by WebRTC applications, as it is common for marking traffic sent by WebRTC applications, as it is common for
multiple RTP streams to be multiplexed on the same transport-layer multiple RTP streams to be multiplexed on the same transport-layer
flow. Generally, the RTP streams would be marked with a value as flow. Generally, the RTP streams would be marked with a value as
appropriate from Table 1. A WebRTC application might also multiplex appropriate from Table 1. A WebRTC application might also multiplex
data channel [I-D.ietf-rtcweb-data-channel] traffic over the same data channel [RFC8831] traffic over the same 5-tuple as RTP streams,
5-tuple as RTP streams, which would also be marked as per that table. which would also be marked per that table. The guidance in [RFC7657]
The guidance in [RFC7657] says that all data channel traffic would be says that all data channel traffic would be marked with a single
marked with a single value that is typically different than the value that is typically different from the value(s) used for RTP
value(s) used for RTP streams multiplexed with the data channel streams multiplexed with the data channel traffic over the same
traffic over the same 5-tuple, assuming RTP streams are marked with a 5-tuple, assuming RTP streams are marked with a value other than
value other than default forwarding (DF). This is expanded upon Default Forwarding (DF). This is expanded upon further in the next
further in the next section. section.
This specification does not change or override the advice in any This specification does not change or override the advice in any
other IETF RFCs about setting packet markings. Rather, it simply other RFCs about setting packet markings. Rather, it simply selects
selects a subset of DSCP values that is relevant in the WebRTC a subset of DSCP values that is relevant in the WebRTC context.
context.
The DSCP value set by the endpoint is not trusted by the network. In The DSCP value set by the endpoint is not trusted by the network. In
addition, the DSCP value may be remarked at any place in the network addition, the DSCP value may be remarked at any place in the network
for a variety of reasons to any other DSCP value, including default for a variety of reasons to any other DSCP value, including the DF
forwarding (DF) value to provide basic best effort service. Even so, value to provide basic best-effort service. Even so, there is a
there is benefit in marking traffic even if it only benefits the benefit to marking traffic even if it only benefits the first few
first few hops. The implications are discussed in Secton 3.2 of hops. The implications are discussed in Section 3.2 of [RFC7657].
[RFC7657]. Further, a mitigation for such action is through an Further, a mitigation for such action is through an authorization
authorization mechanism. Such an authorization mechanism is outside mechanism. Such an authorization mechanism is outside the scope of
the scope of this document. this document.
4. Inputs 4. Inputs
WebRTC applications send and receive two types of flows of This document recommends DSCP values for two classes of WebRTC flows:
significance to this document:
o media flows which are RTP streams [I-D.ietf-rtcweb-rtp-usage] * media flows that are RTP streams [RFC8834]
o data flows which are data channels [I-D.ietf-rtcweb-data-channel] * data flows that are data channels [RFC8831]
Each of the RTP streams and distinct data channels consists of all of Each of the RTP streams and distinct data channels consist of all of
the packets associated with an independent media entity, so an RTP the packets associated with an independent media entity, so an RTP
stream or distinct data channel is not always equivalent to a stream or distinct data channel is not always equivalent to a
transport-layer flow defined by a 5-tuple (source address, transport-layer flow defined by a 5-tuple (source address,
destination address, source port, destination port, and protocol). destination address, source port, destination port, and protocol).
There may be multiple RTP streams and data channels multiplexed over There may be multiple RTP streams and data channels multiplexed over
the same 5-tuple, with each having a different level of importance to the same 5-tuple, with each having a different level of importance to
the application and, therefore, potentially marked using different the application and, therefore, potentially marked using different
DSCP values than another RTP stream or data channel within the same DSCP values than another RTP stream or data channel within the same
transport-layer flow. (Note that there are restrictions with respect transport-layer flow. (Note that there are restrictions with respect
to marking different data channels carried within the same SCTP to marking different data channels carried within the same Stream
association as outlined in Section 5.) Control Transmission Protocol (SCTP) association as outlined in
Section 5.)
The following are the inputs provided by the WebRTC application to The following are the inputs provided by the WebRTC application to
the browser: the browser:
o Flow Type: The application provides this input because it knows if * Flow Type: The application provides this input because it knows if
the flow is audio, interactive video [RFC4594] [G.1010] with or the flow is audio, interactive video ([RFC4594] [G.1010]) with or
without audio, or data. without audio, or data.
o Application Priority: Another input is the relative importance of * Application Priority: Another input is the relative importance of
an RTP stream or data channel. Many applications have multiple an RTP stream or data channel. Many applications have multiple
flows of the same Flow Type and often some flows are more flows of the same flow type and some flows are often 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 flow is high, medium, low or tell the browser whether a particular flow is of High, Medium,
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 [RFC8835] defines in more detail what an individual flow is within
individual flow is within the WebRTC context and priorities for media the WebRTC context and priorities for media and data flows.
and data flows.
Currently in WebRTC, media sent over RTP is assumed to be interactive Currently in WebRTC, media sent over RTP is assumed to be interactive
[I-D.ietf-rtcweb-transports] and browser APIs do not exist to allow [RFC8835] and browser APIs do not exist to allow an application to
an application to to differentiate between interactive and non- differentiate between interactive and non-interactive video.
interactive video.
5. DSCP Mappings 5. DSCP Mappings
The DSCP values for each flow type of interest to WebRTC based on The DSCP values for each flow type of interest to WebRTC based on
application priority are shown in Table 1. These values are based on application priority are shown in Table 1. These values are based on
the framework and recommended values in [RFC4594]. A web browser the framework and recommended values in [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 Expedited Forwarding (EF) and Assured Forwarding (AF)
can be found in [RFC2597]. DF is default forwarding which provides can be found in [RFC3246] and [RFC2597], respectively. DF is Default
the basic best effort service [RFC2474]. Forwarding, which provides the basic best-effort service [RFC2474].
WebRTC use of multiple DSCP values may encounter network blocking of WebRTC's use of multiple DSCP values may result in packets with
packets with certain DSCP values. See section 4.2 of certain DSCP values being blocked by a network. See Section 4.2 of
[I-D.ietf-rtcweb-transports] for further discussion, including how [RFC8835] for further discussion, including how WebRTC
WebRTC implementations establish and maintain connectivity when such implementations establish and maintain connectivity when such
blocking is encountered. blocking is encountered.
+------------------------+-------+------+-------------+-------------+ +=======================+==========+=====+============+============+
| Flow Type | Very | Low | Medium | High | | Flow Type | Very Low | Low | Medium | High |
| | Low | | | | +=======================+==========+=====+============+============+
+------------------------+-------+------+-------------+-------------+ | Audio | LE (1) | DF | EF (46) | EF (46) |
| Audio | CS1 | DF | EF (46) | EF (46) | | | | (0) | | |
| | (8) | (0) | | | +-----------------------+----------+-----+------------+------------+
| | | | | | +-----------------------+----------+-----+------------+------------+
| Interactive Video with | CS1 | DF | AF42, AF43 | AF41, AF42 | | Interactive Video | LE (1) | DF | AF42, AF43 | AF41, AF42 |
| or without Audio | (8) | (0) | (36, 38) | (34, 36) | | with or without Audio | | (0) | (36, 38) | (34, 36) |
| | | | | | +-----------------------+----------+-----+------------+------------+
| Non-Interactive Video | CS1 | DF | AF32, AF33 | AF31, AF32 | +-----------------------+----------+-----+------------+------------+
| with or without Audio | (8) | (0) | (28, 30) | (26, 28) | | Non-Interactive Video | LE (1) | DF | AF32, AF33 | AF31, AF32 |
| | | | | | | with or without Audio | | (0) | (28, 30) | (26, 28) |
| Data | CS1 | DF | AF11 | AF21 | +-----------------------+----------+-----+------------+------------+
| | (8) | (0) | | | +-----------------------+----------+-----+------------+------------+
+------------------------+-------+------+-------------+-------------+ | Data | LE (1) | DF | AF11 | AF21 |
| | | (0) | | |
+-----------------------+----------+-----+------------+------------+
Table 1: Recommended DSCP Values for WebRTC Applications Table 1: Recommended DSCP Values for WebRTC Applications
The application priority, indicated by the columns "very low", "low", The application priority, indicated by the columns "Very Low", "Low",
"Medium", and "high", signifies the relative importance of the flow "Medium", and "High", signifies the relative importance of the flow
within the application. It is an input that the browser receives to within the application. It is an input that the browser receives to
assist in selecting the DSCP value and adjusting the network assist in selecting the DSCP value and adjusting the network
transport behavior. transport behavior.
The above table assumes that packets marked with CS1 are treated as The above table assumes that packets marked with LE are treated as
"less than best effort", such as the LE behavior described in lower effort (i.e., "less than best effort"), such as the LE behavior
[RFC3662]. However, the treatment of CS1 is implementation described in [RFC8622]. However, the treatment of LE is
dependent. If an implementation treats CS1 as other than "less than implementation dependent. If an implementation treats LE as other
best effort", then the actual priority (or, more precisely, the per- than "less than best effort", then the actual priority (or, more
hop-behavior) of the packets may be changed from what is intended. precisely, the per-hop behavior) of the packets may be changed from
It is common for CS1 to be treated the same as DF, so applications what is intended. It is common for LE to be treated the same as DF,
and browsers using CS1 cannot assume that CS1 will be treated so applications and browsers using LE cannot assume that LE will be
differently than DF [RFC7657]. However, it is also possible per treated differently than DF [RFC7657]. During development of this
[RFC2474] for CS1 traffic to be given better treatment than DF, thus document, the CS1 DSCP was recommended for "very low" application
caution should be exercised when electing to use CS1. This is one of priority traffic; implementations that followed that recommendation
the cases where marking packets using these recommendations can make SHOULD be updated to use the LE DSCP instead of the CS1 DSCP.
things worse.
Implementers should also note that excess EF traffic is dropped. Implementers should also note that excess EF traffic is dropped.
This could mean that a packet marked as EF may not get through, This could mean that a packet marked as EF may not get through,
although the same packet marked with a different DSCP value would although the same packet marked with a different DSCP value would
have gotten through. This is not a flaw, but how excess EF traffic have gotten through. This is not a flaw, but how excess EF traffic
is intended to be treated. is intended to be treated.
The browser SHOULD first select the flow type of the flow. Within The browser SHOULD first select the flow type of the flow. Within
the flow type, the relative importance of the flow SHOULD be used to the flow type, the relative importance of the flow SHOULD be used to
select the appropriate DSCP value. select the appropriate DSCP value.
Currently, all WebRTC video is assumed to be interactive Currently, all WebRTC video is assumed to be interactive [RFC8835],
[I-D.ietf-rtcweb-transports], for which the Interactive Video DSCP for which the interactive video DSCP values in Table 1 SHOULD be
values in Table 1 SHOULD be used. Browsers MUST NOT use the AF3x used. Browsers MUST NOT use the AF3x DSCP values (for non-
DSCP values (for Non-Interactive Video in Table 1) for WebRTC interactive video in Table 1) for WebRTC applications. Non-browser
applications. Non-browser implementations of WebRTC MAY use the AF3x implementations of WebRTC MAY use the AF3x DSCP values for video that
DSCP values for video that is known not to be interactive, e.g., all is known not to be interactive, e.g., all video in a WebRTC video
video in a WebRTC video playback application that is not implemented playback application that is not implemented in a browser.
in a browser.
The combination of flow type and application priority provides The combination of flow type and application priority provides
specificity and helps in selecting the right DSCP value for the flow. specificity and helps in selecting the right DSCP value for the flow.
All packets within a flow SHOULD have the same application priority. All packets within a flow SHOULD have the same application priority.
In some cases, the selected application priority cell may have In some cases, the selected application priority cell may have
multiple DSCP values, such as AF41 and AF42. These offer different multiple DSCP values, such as AF41 and AF42. These offer different
drop precedences. The different drop precedence values provides drop precedences. The different drop precedence values provide
additional granularity in classifying packets within a flow. For additional granularity in classifying packets within a flow. For
example, in a video conference the video flow may have medium example, in a video conference, the video flow may have medium
application priority, thus either AF42 or AF43 may be selected. More application priority, thus either AF42 or AF43 may be selected. More
important video packets (e.g., a video picture or frame encoded important video packets (e.g., a video picture or frame encoded
without any dependency on any prior pictures or frames) might be without any dependency on any prior pictures or frames) might be
marked with AF42 and less important packets (e.g., a video picture or marked with AF42 and less important packets (e.g., a video picture or
frame encoded based on the content of one or more prior pictures or frame encoded based on the content of one or more prior pictures or
frames) might be marked with AF43 (e.g., receipt of the more frames) might be marked with AF43 (e.g., receipt of the more
important packets enables a video renderer to continue after one or important packets enables a video renderer to continue after one or
more packets are lost). more packets are lost).
It is worth noting that the application priority is utilized by the It is worth noting that the application priority is utilized by the
coupled congestion control mechanism for media flows per coupled congestion control mechanism for media flows per [RFC8699]
[I-D.ietf-rmcat-coupled-cc] and the SCTP scheduler for data channel and the SCTP scheduler for data channel traffic per [RFC8831].
traffic per [I-D.ietf-rtcweb-data-channel].
For reasons discussed in Section 6 of [RFC7657], if multiple flows For reasons discussed in Section 6 of [RFC7657], if multiple flows
are multiplexed using a reliable transport (e.g., TCP) then all of are multiplexed using a reliable transport (e.g., TCP), then all of
the packets for all flows multiplexed over that transport-layer flow the packets for all flows multiplexed over that transport-layer flow
MUST be marked using the same DSCP value. Likewise, all WebRTC data MUST be marked using the same DSCP value. Likewise, all WebRTC data
channel packets transmitted over an SCTP association MUST be marked channel packets transmitted over an SCTP association MUST be marked
using the same DSCP value, regardless of how many data channels using the same DSCP value, regardless of how many data channels
(streams) exist or what kind of traffic is carried over the various (streams) exist or what kind of traffic is carried over the various
SCTP streams. In the event that the browser wishes to change the SCTP streams. In the event that the browser wishes to change the
DSCP value in use for an SCTP association, it MUST reset the SCTP DSCP value in use for an SCTP association, it MUST reset the SCTP
congestion controller after changing values. Frequent changes in the congestion controller after changing values. However, frequent
DSCP value used for an SCTP association are discouraged, though, as changes in the DSCP value used for an SCTP association are
this would defeat any attempts at effectively managing congestion. discouraged, as this would defeat any attempts at effectively
It should also be noted that any change in DSCP value that results in managing congestion. It should also be noted that any change in DSCP
a reset of the congestion controller puts the SCTP association back value that results in a reset of the congestion controller puts the
into slow start, which may have undesirable effects on application SCTP association back into slow start, which may have undesirable
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
flows over a TCP connection, the DCSP value selected should be the flows over a TCP connection, the DSCP value selected SHOULD be 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 network that has no support for a flow type- If a packet enters a network that has no support for a flow-type-
application priority combination specified in Table 1, then the application priority combination specified in Table 1, 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 flow not getting the network policies. This could result in the flow not getting the network
treatment it expects based on the original DSCP value in the packet. treatment it expects based on the original DSCP value in the packet.
Subsequently, if the packet enters a network that supports a larger Subsequently, if the packet enters a network that supports a larger
number of these combinations, there may not be sufficient information number of these combinations, there may not be sufficient information
in the packet to restore the original markings. Mechanisms for in the packet to restore the original markings. Mechanisms for
restoring such original DSCP is outside the scope of this document. restoring such original DSCP is outside the scope of this document.
In summary, DSCP marking provides neither guarantees nor promised In summary, DSCP marking provides neither guarantees nor promised
skipping to change at page 8, line 37 skipping to change at line 350
path, as well as the network conditions at every hop. path, as well as the network conditions at every hop.
6. Security Considerations 6. Security Considerations
Since the JavaScript application specifies the flow type and Since the JavaScript application specifies the flow type and
application priority that determine the media flow DSCP values used application priority that determine the media flow DSCP values used
by the browser, the browser could consider application use of a large by the browser, the browser could consider application use of a large
number of higher priority flows to be suspicious. If the server number of higher priority flows to be suspicious. If the server
hosting the JavaScript application is compromised, many browsers hosting the JavaScript application is compromised, many browsers
within the network might simultaneously transmit flows with the same within the network might simultaneously transmit flows with the same
DSCP marking. The DiffServ architecture requires ingress traffic DSCP marking. The Diffserv architecture requires ingress traffic
conditioning for reasons that include protecting the network from conditioning for reasons that include protecting the network from
this sort of attack. this sort of attack.
Otherwise, this specification does not add any additional security Otherwise, this specification does not add any additional security
implications beyond those addressed in the following DSCP-related implications beyond those addressed in the following DSCP-related
specifications. For security implications on use of DSCP, please specifications. For security implications on use of DSCP, please
refer to Section 7 of [RFC7657] and Section 6 of [RFC4594]. Please refer to Section 7 of [RFC7657] and Section 6 of [RFC4594]. Please
also see [I-D.ietf-rtcweb-security] as an additional reference. also see [RFC8826] as an additional reference.
7. IANA Considerations 7. IANA Considerations
This specification does not require any actions from IANA. This document has no IANA actions.
8. Downward References 8. Downward References
This specification contains a downwards reference to [RFC4594] and This specification contains downwards references to [RFC4594] and
[RFC7657]. However, the parts of the former RFC used by this [RFC7657]. However, the parts of the former RFCs used by this
specification are sufficiently stable for this downward reference. specification are sufficiently stable for these downward references.
The guidance in the latter RFC is necessary to understand the The guidance in the latter RFC is necessary to understand the
Diffserv technology used in this document and the motivation for the Diffserv technology used in this document and the motivation for the
recommended DSCP values and procedures. recommended DSCP values and procedures.
9. Acknowledgements 9. References
Thanks to David Black, Magnus Westerlund, Paolo Severini, Jim
Hasselbrook, Joe Marcus, Erik Nordmark, Michael Tuexen, and Brian
Carpenter for their invaluable input.
10. Dedication
This document is dedicated to the memory of James Polk, a long-time
friend and colleague. James made important contributions to this
specification, including serving initially as one of the primary
authors. The IETF global community mourns his loss and he will be
missed dearly.
11. 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.
12. References 9.1. Normative References
12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[I-D.ietf-rtcweb-data-channel] [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Guidelines for DiffServ Service Classes", RFC 4594,
Channels", draft-ietf-rtcweb-data-channel-13 (work in DOI 10.17487/RFC4594, August 2006,
progress), January 2015. <https://www.rfc-editor.org/info/rfc4594>.
[I-D.ietf-rtcweb-rtp-usage] [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
Perkins, D., Westerlund, M., and J. Ott, "Web Real-Time (Diffserv) and Real-Time Communication", RFC 7657,
Communication (WebRTC): Media Transport and Use of RTP", DOI 10.17487/RFC7657, November 2015,
draft-ietf-rtcweb-rtp-usage-26 (work in progress), March <https://www.rfc-editor.org/info/rfc7657>.
2016.
[I-D.ietf-rtcweb-security] [RFC7742] Roach, A.B., "WebRTC Video Processing and Codec
Rescorla, E., "Security Considerations for WebRTC", draft- Requirements", RFC 7742, DOI 10.17487/RFC7742, March 2016,
ietf-rtcweb-security-08 (work in progress), February 2015. <https://www.rfc-editor.org/info/rfc7742>.
[I-D.ietf-rtcweb-transports] [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
Alvestrand, H., "Transports for WebRTC", draft-ietf- 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
rtcweb-transports-15 (work in progress), August 2016. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC8622] Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Differentiated Services", RFC 8622, DOI 10.17487/RFC8622,
RFC2119, March 1997, June 2019, <https://www.rfc-editor.org/info/rfc8622>.
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration [RFC8826] Rescorla, E., "Security Considerations for WebRTC",
Guidelines for DiffServ Service Classes", RFC 4594, DOI RFC 8826, DOI 10.17487/RFC8826, January 2021,
10.17487/RFC4594, August 2006, <https://www.rfc-editor.org/info/rfc8826>.
<http://www.rfc-editor.org/info/rfc4594>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services [RFC8831] Jesup, R., Loreto, S., and M. Tüxen, "WebRTC Data
(Diffserv) and Real-Time Communication", RFC 7657, DOI Channels", RFC 8831, DOI 10.17487/RFC8831, January 2021,
10.17487/RFC7657, November 2015, <https://www.rfc-editor.org/info/rfc8831>.
<http://www.rfc-editor.org/info/rfc7657>.
[RFC7742] Roach, A., "WebRTC Video Processing and Codec [RFC8834] Perkins, C., Westerlund, M., and J. Ott, "Media Transport
Requirements", RFC 7742, DOI 10.17487/RFC7742, March 2016, and Use of RTP in WebRTC", RFC 8834, DOI 10.17487/RFC8834,
<http://www.rfc-editor.org/info/rfc7742>. January 2021, <https://www.rfc-editor.org/info/rfc8834>.
12.2. Informative References [RFC8835] Alvestrand, H., "Transports for WebRTC", RFC 8835,
DOI 10.17487/RFC8835, January 2021,
<https://www.rfc-editor.org/info/rfc8835>.
[G.1010] International Telecommunications Union, "End-user 9.2. Informative References
multimedia QoS categories", Recommendation ITU-T G.1010,
November 2001.
[I-D.ietf-rmcat-coupled-cc] [G.1010] ITU-T, "End-user multimedia QoS categories", ITU-T
Islam, S., Welzl, M., and S. Gjessing, "Coupled congestion Recommendation G.1010, November 2001,
control for RTP media", draft-ietf-rmcat-coupled-cc-03 <https://www.itu.int/rec/T-REC-G.1010-200111-I/en>.
(work in progress), July 2016.
[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, DOI Field) in the IPv4 and IPv6 Headers", RFC 2474,
10.17487/RFC2474, December 1998, DOI 10.17487/RFC2474, December 1998,
<http://www.rfc-editor.org/info/rfc2474>. <https://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, DOI 10.17487/ "Assured Forwarding PHB Group", RFC 2597,
RFC2597, June 1999, DOI 10.17487/RFC2597, June 1999,
<http://www.rfc-editor.org/info/rfc2597>. <https://www.rfc-editor.org/info/rfc2597>.
[RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, [RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le
J., Courtney, W., Davari, S., Firoiu, V., and D. Boudec, J.Y., 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, DOI 10.17487/RFC3246, March 2002, Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<http://www.rfc-editor.org/info/rfc3246>. <https://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, <https://www.rfc-editor.org/info/rfc3550>.
[RFC3662] Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort [RFC8699] Islam, S., Welzl, M., and S. Gjessing, "Coupled Congestion
Per-Domain Behavior (PDB) for Differentiated Services", Control for RTP Media", RFC 8699, DOI 10.17487/RFC8699,
RFC 3662, DOI 10.17487/RFC3662, December 2003, January 2020, <https://www.rfc-editor.org/info/rfc8699>.
<http://www.rfc-editor.org/info/rfc3662>.
Acknowledgements
Thanks to David Black, Magnus Westerlund, Paolo Severini, Jim
Hasselbrook, Joe Marcus, Erik Nordmark, Michael Tüxen, and Brian
Carpenter for their invaluable input.
Dedication
This document is dedicated to the memory of James Polk, a long-time
friend and colleague. James made important contributions to this
specification, including serving initially as one of the primary
authors. The IETF global community mourns his loss and he will be
missed dearly.
Authors' Addresses Authors' Addresses
Paul E. Jones Paul E. Jones
Cisco Systems Cisco Systems
Email: paulej@packetizer.com Email: paulej@packetizer.com
Subha Dhesikan Subha Dhesikan
Cisco Systems Individual
Email: sdhesika@cisco.com Email: sdhesikan@gmail.com
Cullen Jennings Cullen Jennings
Cisco Systems Cisco Systems
Email: fluffy@cisco.com Email: fluffy@cisco.com
Dan Druta Dan Druta
AT&T AT&T
Email: dd5826@att.com Email: dd5826@att.com
 End of changes. 70 change blocks. 
240 lines changed or deleted 224 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/