[Fecframe] My comments around draft-begen-fecframe-1d2d-parity-scheme-00

[Magnus Westerlund <[e-mail]>]

Hi,

In today's WG session I did appear quite negative to this draft. I am 
sorry that I wasn't better prepared and had read and thought about this 
before.

Let me try to put down my comments here and with some hindsight.

- Appropriateness in the FEC framework: Yes, this does fit the framework 
as a rather speciallized FEC code that results in one repair stream for 
every SSRC in a single RTP session. That is quite far from a more 
generic FEC scheme that can take multiple streams and combine them etc. 
   In fact it is very similar to the already existing RTP payload level 
FEC mechanisms like ULP (RFC5109). Thus, it seem to leverage very little 
of the framework and instead be very much something that could be done 
in AVT.

- The selection of RTP/UDP as repair stream transport layer. I don't 
think this really is a FEC scheme but rather a instantiation of the FEC 
framework using a component that haven't been much discussed to my 
knowledge. I do understand that it can provide feedback on how well the 
repair stream is delivered to the receiver(s). Which actually is a good 
point for general deployment. However in that case one maybe need to 
consider what general feedback that a FEC framework instance should 
provide towards the sender, i.e. including both source and repair stream 
related statistics. Something to think about and actually should make it 
way into the framework.

So I primarily would like to get the issue of the repair stream feedback 
mechanism and what the WG think is suitable for this before this is 
adopted anywhere.

Cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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Multimedia Technologies, Ericsson Research EAB/TVM
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