Re: [AVTCORE] I-D Action: draft-ietf-avtcore-rtp-circuit-breakers-11.txt

Colin Perkins <> Mon, 19 October 2015 10:17 UTC

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Subject: Re: [AVTCORE] I-D Action: draft-ietf-avtcore-rtp-circuit-breakers-11.txt
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> On 16 Oct 2015, at 17:30, wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Audio/Video Transport Core Maintenance Working Group of the IETF.
>        Title           : Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions
>        Authors         : Colin Perkins
>                          Varun Singh
> 	Filename        : draft-ietf-avtcore-rtp-circuit-breakers-11.txt
> 	Pages           : 23
> 	Date            : 2015-10-16
> Abstract:
>   The Real-time Transport Protocol (RTP) is widely used in telephony,
>   video conferencing, and telepresence applications.  Such applications
>   are often run on best-effort UDP/IP networks.  If congestion control
>   is not implemented in the applications, then network congestion will
>   deteriorate the user's multimedia experience.  This document does not
>   propose a congestion control algorithm; instead, it defines a minimal
>   set of RTP circuit-breakers.  Circuit-breakers are conditions under
>   which an RTP sender needs to stop transmitting media data in order to
>   protect the network from excessive congestion.  It is expected that,
>   in the absence of severe congestion, all RTP applications running on
>   best-effort IP networks will be able to run without triggering these
>   circuit breakers.  Any future RTP congestion control specification
>   will be expected to operate within the constraints defined by these
>   circuit breakers.
> The IETF datatracker status page for this draft is:
> There's also a htmlized version available at:
> A diff from the previous version is available at:

This version of the draft is a major update, that makes the following changes:

- Update the media timeout circuit breaker to address the over- and under-sampling issues raised by Magnus Westerlund, by taking into account the RTT and RTP framing interval in the calculation, as well as the RTCP reporting interval.

- Update the congestion circuit breaker to address the over- and under-sampling issues raised by Magnus Westerlund, and to account for codecs that cannot change their rate on each frame, by modifying the definition of CB_INTERVAL to include the RTP framing interval, the frame group size, and the RTT in the calculation, as well as the RTCP reporting interval.

- Collect definitions and clarify terminology.

- Clarify behaviour when interworking with systems that don’t implement RTCP, based on feedback by Simon Perreault.

- Remove discussion on Impact of RTCP Reporting Groups, that seemed to confuse rather than clarify.

- Various editorial fixes to address other review comments by Simon Perreault, and make assorted other corrections. 

Feedback welcome. 


Colin Perkins