[AVTCORE] Mirja Kühlewind's Discuss on draft-ietf-avtcore-rtp-circuit-breakers-15: (with DISCUSS and COMMENT)

"Mirja Kuehlewind" <ietf@kuehlewind.net> Tue, 03 May 2016 12:03 UTC

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Mirja Kühlewind has entered the following ballot position for
draft-ietf-avtcore-rtp-circuit-breakers-15: Discuss

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DISCUSS:
----------------------------------------------------------------------

This is about one point in section 7 (ECN) that I think is wrong but I
would like to get some feedback from the authors:
"then ECN-CE marked packets SHOULD
   be treated as if they were lost when calculating if the congestion-
   based RTP circuit breaker"
(also section 5: "The count of ECN-CE marked packets
   contained in those ECN feedback reports is counted towards the number
   of lost packets reported")

We are currently discussion mechanisms where the AQM in the congested
network node sends  much more CE markings than one would see loss (when
using TCP) for the same level of congestion. When treating ECN-CE similar
to loss, such a different behavior could trigger the circuit breaker
unnecessarily. Potentially ECN-CE might not need to be considered here at
all, because as long as there are (only) ECN-CE marks (and no loss) all
data is transmitted correctly to the receiver and therefore there is no
need to trigger a circuit breaker.

Further also in section 7: "ECN-CE marked packets SHOULD be treated as if
they were lost for the
   purposes of congestion control"

This document should not impose any SHOULDs for congestion control as
this doc is only about circuit breaker sand therefore the sentence above
should be removed.


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COMMENT:
----------------------------------------------------------------------

Few more minor comments:

1) reference [I-D.ietf-tsvwg-circuit-breaker] should be normative
2) How is the loss rate in 4.3 calculated if some (but no all) RR are
lost?
3) I don't think that most of the text on congestion control in section 2
(as well as the abstract) is necessary for this doc (but it also don't
really hurt)