From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Subject: WG Review: RTP Media Congestion Avoidance Techniques (rmcat)
A new IETF working group has been proposed in the Transport Area. The
IESG has not made any determination yet. The following draft charter was
submitted, and is provided for informational purposes only. Please send
your comments to the IESG mailing list (iesg at ietf.org) by 2012-09-12.
RTP Media Congestion Avoidance Techniques (rmcat)
------------------------------------------------
Current Status: Proposed Working Group
Assigned Area Director:
Wesley Eddy <wes@mti-systems.com>
Charter of Working Group:
Description of Working Group
Today's Internet traffic includes interactive real-time media, which is
often carried via sets of flows using RTP over UDP. There is no generally accepted
congestion control mechanism for this kind of data flow. With the deployment of
applications using the RTCWEB protocol suite, the number of such flows is likely to
increase, especially non-fixed-rate flows such as video or adaptive audio. There is
therefore some urgency in specifying one or more congestion control mechanisms that
can find general acceptance.
Congestion control algorithms for interactive real time media may need to
be quite different from the congestion control of TCP: for example, some
applications can be more tolerant to loss than delay and jitter. The set of
requirements for such an algorithm includes, but is not limited to:
- Low delay and low jitter for the case where there is no competing
traffic using other algorithms
- Reasonable share of bandwidth when competing with RMCAT traffic,
other real-time media protocols, and ideally also TCP and other
protocols. A 'reasonable share' means that no flow has a significantly negative
impact [RFC5033] on other flows and at minimum that no flow starves.
- Effective use of signals like packet loss and ECN markings to adapt
to congestion
The working group will:
- Develop a clear understanding of the congestion control
requirements for RTP flows, and document deficiencies of existing mechanisms such as
TFRC with regards to these requirements. This must be completed prior to
finishing any Experimental algorithm specifications.
- Identify interactions between applications and RTP flows to enable
conveying helpful cross-layer information such as per-packet priorities, flow
elasticity, etc. This information might be used to populate an API, but the WG will
not define a specific API itself.
- Determine if extensions to RTP/RTCP are needed for carrying
congestion control feedback, using DCCP as a model. If so, provide the
requirements for such extensions to the AVTCORE working group for
standardization there.
- Develop techniques to detect, instrument or diagnose failing to
meet RT schedules due to failures of components outside of the charter
scope, possibly in collaboration with IPPM.
- Develop a mechanism for identifying shared bottlenecks between
groups of flows, and means to flexibly allocate their rates within the
aggregate hitting the shared bottleneck.
- Define evaluation criteria for proposed congestion control
mechanisms, and publish these as an Informational RFC. This must be completed
prior to finishing any Proposed Standard algorithm specifications.
- Find or develop candidate congestion control algorithms, verify
that these can be tested on the Internet without significant risk, and publish one or
more of these as Experimental RFCs.
- Publish evaluation criteria and the result of experimentation with
these Experimental algorithms on the Internet. This must be completed
prior to finishing any Proposed Standard algorithm specifications.
- Once an algorithm has been found or developed that meets the
evaluation criteria, and has a satisfactory amount of documented experience on
the Internet, publish this algorithm as a Standards Track RFC. There
may be more than one such algorithm.
- For each of the Experimental algorithms that have not been selected
for the Standards Track, the working group will review the algorithm and
determine whether the RFC should be moved to Historic status via a document
that briefly describes the issues encountered. This step is
particularly important for algorithms with significant flaws, such as ones that turn out
to be harmful to flows using or competing with them.
The work will be guided by the advice laid out in RFC 5405 (UDP Usage
Guidelines), RFC 2914 (congestion control principles), and RFC5033 (Specifying New
Congestion Control Algorithms).
The following topics are out of scope of this working group, on the
assumption that work on them will proceed elsewhere:
- Circuit-breaker algorithms for stopping media flows when network
conditions render them useless; this work is done in AVTCORE
- Media flows for non-interactive purposes like stored video
playback; those are not as delay sensitive as interactive traffic
- Defining active queue management algorithms or modifications to TCP
of any kind
- Multicast congestion control; common control of multiple unicast
flows is in scope
- Topologies other than point-to-point connections; implications on
multi-hop connections will be considered at a later stage
The working group is expected to work closely with the RAI area,
including the underlying technologies being worked on in the AVTCORE and AVTEXT WGs,
and the applications/protocol suites being developed in the CLUE and RTCWEB
working groups. It will also coordinate closely with other Transport area groups
working on congestion control, and with the Internet Congestion Control Research
Group of the IRTF.
Deliverables:
- Requirements for congestion control algorithms for interactive real
time media as an Informational RFC
- Evaluation criteria for congestion control algorithms for
interactive real time media as an Informational RFC
- RTCP extensions for use with congestion control algorithms as a
Proposed Standard RFC
- Interactions between applications and RTP flows as an Informational
RFC
- Identifying and controlling groups of flows as a Proposed Standard
RFC
- Techniques to detect, instrument or diagnose failing to meet RT
schedules as either an Informational RFC or on the Standards Track if
needed for interoperability or other aspects that would justify it.
- Candidate congestion control algorithm for interactive real time
media as Experimental RFCs (likely more than one)
- Experimentation and evaluation results for candidate congestion
control algorithms as an Informational RFC
- One or more recommended congestion control algorithms for
interactive real time media as Proposed Standard RFCs
Milestones:
WG action announcement
WG Action Announcement
From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: rmcat WG <rmcat@ietf.org>
Subject: WG Action: Formed RTP Media Congestion Avoidance Techniques (rmcat)
A new IETF working group has been formed in the Transport Area. For
additional information please contact the Area Directors or the WG
Chairs.
RTP Media Congestion Avoidance Techniques (rmcat)
------------------------------------------------
Current Status: Proposed Working Group
Chairs:
Lars Eggert <lars@netapp.com>
Mirja Kuehlewind <mirja.kuehlewind@ikr.uni-stuttgart.de>
Assigned Area Director:
Wesley Eddy <wes@mti-systems.com>
Mailing list
Address: rmcat@ietf.org
To Subscribe: https://www.ietf.org/mailman/listinfo/rmcat
Archive: http://www.ietf.org/mail-archive/web/rmcat/
Charter of Working Group:
Today's Internet traffic includes interactive real-time media, which is
often carried via sets of flows using RTP over UDP. There is no
generally accepted congestion control mechanism for this kind of data
flow. With the deployment of applications using the RTCWEB protocol
suite, the number of such flows is likely to increase, especially non-
fixed-rate flows such as video or adaptive audio. There is therefore
some urgency in specifying one or more congestion control mechanisms
that can find general acceptance.
Congestion control algorithms for interactive real time media may need
to be quite different from the congestion control of TCP: for example,
some applications can be more tolerant to loss than delay and jitter.
The set of requirements for such an algorithm includes, but is not
limited to:
- Low delay and low jitter for the case where there is no competing
traffic using other algorithms
- Reasonable share of bandwidth when competing with RMCAT traffic,
other real-time media protocols, and ideally also TCP and other
protocols. A 'reasonable share' means that no flow has a
significantly negative impact [RFC5033] on other flows and at
minimum that no flow starves.
- Effective use of signals like packet loss and ECN markings to
adapt to congestion
The working group will:
- Develop a clear understanding of the congestion control
requirements for RTP flows, and document deficiencies of existing
mechanisms such as TFRC with regards to these requirements. This
must be completed prior to finishing any Experimental algorithm
specifications.
- Identify interactions between applications and RTP flows to enable
conveying helpful cross-layer information such as per-packet
priorities, flow elasticity, etc. This information might be used
to populate an API, but the WG will not define a specific API
itself.
- Determine if extensions to RTP/RTCP are needed for carrying
congestion control feedback, using DCCP as a model. If so,
provide the requirements for such extensions to the AVTCORE
working group for standardization there.
- Develop techniques to detect, instrument or diagnose failing to
meet RT schedules due to failures of components outside of the
charter scope, possibly in collaboration with IPPM.
- Develop a mechanism for identifying shared bottlenecks between
groups of flows, and means to flexibly allocate their rates within
the aggregate hitting the shared bottleneck.
- Define evaluation criteria for proposed congestion control
mechanisms, and publish these as an Informational RFC. This must
be completed prior to finishing any Proposed Standard algorithm
specifications.
- Find or develop candidate congestion control algorithms, verify
that these can be tested on the Internet without significant risk,
and publish one or more of these as Experimental RFCs.
- Publish evaluation criteria and the result of experimentation with
these Experimental algorithms on the Internet. This must be
completed prior to finishing any Proposed Standard algorithm
specifications.
- Once an algorithm has been found or developed that meets the
evaluation criteria, and has a satisfactory amount of documented
experience on the Internet, publish this algorithm as a Standards
Track RFC. There may be more than one algorithm; in this case it
will be one of the objects of the experimentation to determine the
applicabilities and relative merits of the algorithms.
- For each of the Experimental algorithms that have not been
selected for the Standards Track, the working group will review
the algorithm and determine whether there are significant flaws,
such as ones that turn out to be harmful to flows using or
competing with them. If so, the WG will write a document
describing the issues encountered and recommending to the IESG
to move the specification to Historic status.
The work will be guided by the advice laid out in RFC 5405 (UDP Usage
Guidelines), RFC 2914 (congestion control principles), and RFC5033
(Specifying New Congestion Control Algorithms).
The following topics are out of scope of this working group, on the
assumption that work on them will proceed elsewhere:
- Circuit-breaker algorithms for stopping media flows when network
conditions render them useless; this work is done in AVTCORE
- Media flows for non-interactive purposes like stored video
playback; those are not as delay sensitive as interactive traffic
- Defining active queue management algorithms or modifications to
TCP of any kind
- Multicast congestion control; common control of multiple unicast
flows is in scope
- Topologies other than point-to-point connections; implications on
multi-hop connections will be considered at a later stage
The working group is expected to work closely with the RAI area,
including the underlying technologies being worked on in the AVTCORE and
AVTEXT WGs, and the applications/protocol suites being developed in the
CLUE and RTCWEB working groups. It will also coordinate closely with
other Transport area groups working on congestion control, and with the
Internet Congestion Control Research Group of the IRTF.
Deliverables:
- Requirements for congestion control algorithms for interactive
real time media as an Informational RFC
- Evaluation criteria for congestion control algorithms for
interactive real time media as an Informational RFC
- Requirements for RTCP extensions for use with congestion control
algorithms as an input to the AVTCORE WG.
- Interactions between applications and RTP flows as an
Informational RFC
- Identifying and controlling groups of flows as a Proposed Standard
RFC
- Techniques to detect, instrument or diagnose failing to meet RT
schedules as either an Informational RFC or on the Standards Track
if needed for interoperability or other aspects that would justify
it.
- Candidate congestion control algorithm for interactive real time
media as Experimental RFCs (likely more than one)
- Experimentation and evaluation results for candidate congestion
control algorithms as an Informational RFC
- One or more recommended congestion control algorithms for
interactive real time media as Proposed Standard RFCs
Milestones:
Dec 2012 - Adopt first WG drafts of requirements and evaluation
criteria
Dec 2012 - Adopt first WG draft of RTCP extensions for use with
congestion control algorithms and interactions between applications and
RTP flows (if needed)
Jan 2013 - Adopt first congestion control candidate as WG draft
Jan 2013 - Adopt first WG draft on identifying and controlling groups
of flows
Mar 2013 - Submit requirements and evaluation criteria to IESG as
Informational
May 2013 - Submit RTCP extension requirements for use with congestion
control algorithms to AVTCORE (if needed)
May 2013 - Submit interactions between applications and RTP flows to
IESG as Informational
Jun 2013 - Submit first congestion control candidate to IESG for
Experimental publication
Jul 2013 - Submit identifying and controlling groups of flows to IESG
for Standards Track publication
Sep 2013 - Publish first draft of evaluation results
Sep 2013 - Publish first draft of Standards Track congestion control
algorithm
Sep 2013 - Publish first draft of techniques to detect, instrument or
diagnose failing to meet RT schedules
Mar 2014 - Submit techniques to detect, instrument or diagnose failing
to meet RT schedules to IESG as Informational
May 2014 - Submit congestion control to IESG for Proposed Standard