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RTP Media Congestion Avoidance Techniques (Active WG)
Tsv Area: Mirja Kühlewind, Spencer Dawkins | 2012-Sep-25 —  
Chairs
 
 
 


2017-10-23 charter

RTP Media Congestion Avoidance Techniques (rmcat)
-------------------------------------------------

 Charter

 Current Status: Active

 Chairs:
     Anna Brunstrom <anna.brunstrom@kau.se>
     Colin Perkins <csp@csperkins.org>
     Martin Stiemerling <mls.ietf@gmail.com>

 Transport Area Directors:
     Spencer Dawkins <spencerdawkins.ietf@gmail.com>
     Mirja Kühlewind <ietf@kuehlewind.net>

 Transport Area Advisor:
     Mirja Kühlewind <ietf@kuehlewind.net>

 Mailing Lists:
     General Discussion: rmcat@ietf.org
     To Subscribe:       https://www.ietf.org/mailman/listinfo/rmcat
     Archive:            https://mailarchive.ietf.org/arch/browse/rmcat/

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 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

Goals and Milestones:
  Done     -  Adopt first WG draft on requirements
  Done     - Adopt first WG draft on evaluation criteria
  Done     - Adopt first WG draft of RTCP extensions for use with congestion control algorithms and interactions between applications and RTP flows (if needed)
  Done     - Adopt first congestion control candidate as WG draft
  Done     - Adopt first WG draft on identifying and controlling groups of flows
  Jul 2017 - Submit identifying and controlling groups of flows to IESG for Experimental publication
  Jul 2017 - Submit first congestion control candidate to IESG for Experimental publication
  Aug 2017 - Submit RTCP extension requirements for use with congestion control algorithms to AVTCORE (if needed)
  Aug 2017 - Submit requirements and evaluation criteria to IESG as Informational
  Mar 2018 - Submit interactions between applications and RTP flows to IESG as Informational
  Mar 2018 - Publish first draft of evaluation results
  Mar 2018 - Publish first draft of Standards Track congestion control algorithm
  Mar 2018 - Publish first draft of techniques to detect, instrument or diagnose failing to meet RT schedules
  Jul 2018 - Submit techniques to detect, instrument or diagnose failing to meet RT schedules to IESG as Informational
  Nov 2018 - Submit congestion control to IESG for Proposed Standard


All charter page changes, including changes to draft-list, rfc-list and milestones:



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