Re: [AVTCORE] Stephen Farrell's No Objection on draft-ietf-avtcore-rtp-circuit-breakers-15: (with COMMENT)

Colin Perkins <csp@csperkins.org> Tue, 10 May 2016 15:41 UTC

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From: Colin Perkins <csp@csperkins.org>
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Date: Tue, 10 May 2016 16:41:37 +0100
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To: Ben Campbell <ben@nostrum.com>
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Cc: avtcore-chairs@ietf.org, Magnus Westerlund <magnus.westerlund@ericsson.com>, draft-ietf-avtcore-rtp-circuit-breakers@ietf.org, avt@ietf.org, The IESG <iesg@ietf.org>, Stephen Farrell <stephen.farrell@cs.tcd.ie>
Subject: Re: [AVTCORE] Stephen Farrell's No Objection on draft-ietf-avtcore-rtp-circuit-breakers-15: (with COMMENT)
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> On 4 May 2016, at 16:00, Ben Campbell <ben@nostrum.com> wrote:
> 
> On 4 May 2016, at 5:39, Colin Perkins wrote:
> 
> [...]
> 
>>> ----------------------------------------------------------------------
>>> COMMENT:
>>> ----------------------------------------------------------------------
>>> 
>>> 
>>> I just have a nit and a random query...
>>> 
>>> - nit: The abstract says "It is expected that future
>>> standards-track congestion control algorithms for RTP will
>>> operate within the envelope defined by this memo." That
>>> seems both unwise and unlikely to work to me. Unwise in
>>> that you're trying to control the future which seems like
>>> it'll just generate heat and not light, and unlikely to
>>> work since it's not clear to me that any CC scheme can
>>> take into account circuit breaker constants configured on
>>> a node that may not be known anywhere else. I'd say better
>>> would be to say that we hope that future CC algorithms
>>> will be consistent with this and leave it at that.
>>> However, if that sentence is the product of a bunch of
>>> haggling then it's probably better to leave it as-is and
>>> I'll just hold my nose a bit;-) (Same sentence is in the
>>> intro - same comment.)
>> 
>> In some sense, it’s stating the obvious. If an endpoint implements the RTP circuit breaker, which will stop the flow if packet loss exceeds a certain threshold, then any congestion control running in parallel had better make sure the packet loss rate staying below that threshold if it wants the flow to continue. I’m open to suggestions to improve the text.
> 
> How about restating it to describe the consequences if a parallel congestion control allows packet loss rates to exceed the threshold?

“To avoid triggering the RTP circuit breaker, any standards-track congestion control algorithms defined for RTP will need to operate within the envelope set by the RTP circuit breaker algorithms”? 

Or “…will need to keep packet loss rates within the envelope permitted by the RTP circuit breaker algorithm”?

Colin



-- 
Colin Perkins
https://csperkins.org/