Subject: Re: [AVTCORE] draft-ietf-avtcore-ecn-for-rtp-00.txt: What to do if "ecn-fb" has not been negotiated via rtcp.fb attribute?

From: Magnus Westerlund <[email-masked]>
Date: Thu, 10 Mar 2011 16:22:07 +0100

Magnus Westerlund skrev 2011-02-23 09:12:
> Belling, Thomas (NSN - DE/Munich) skrev 2011-02-23 03:07:
>> Hi Magnus,
>>
>> please note that the agreed procedures in TS 26.114 currently do not assume the behaviour discussed in this thread from peers, as we deemed it safer not to take any such assumptions.
>>
>> Although the question poped up when we were preparing the procedures.
>>
>> So you believe such a recommendation is not appropriate?
> 
> I think there can be an informative pointer to that in advanced use case
> beyond what is defined in here, it is important to watch the RTCP-FB
> attribute for what messages really should be used in a session.
> 

Hi I wanted to follow up on the above.

I have looked on what is written and would like to point at Section 7.1:

The "ecn-capable-rtp" SDP attribute MUST always be used when employing
ECN for RTP according to this specification. As the XR ECN summary
report is required independently of the initialization method, or
congestion control scheme the "rtcp-xr" attribute with the "ecn-sum"
parameter MUST also be used. The "rtcp-fb" attribute with the "nack"
parameter "ecn" MUST be used whenever the initialization method or a
congestion control algorithm requiring timely sender side knowledge of
received CE markings. If the congestion control scheme uses additional
signalling they should be indicated as appropriate for those signalling
methods.

All except the last sentence was present in the 00 version. I suggest
that we add the last sentence to make it clear that there may be
additional signalling requirements for some congestion control schemes.

Cheers

Magnus Westerlund

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