[AVTCORE] Discuss on draft-ietf-avt-forward-shifted-red-06

Magnus Westerlund <magnus.westerlund@ericsson.com> Thu, 19 May 2011 07:30 UTC

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Date: Thu, 19 May 2011 09:30:32 +0200
From: Magnus Westerlund <magnus.westerlund@ericsson.com>
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Subject: [AVTCORE] Discuss on draft-ietf-avt-forward-shifted-red-06
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Peter Saint-Andre has one part of his discuss which I believe we need WG
input on.

> 1) It is not clear to me why this document is registering 2 new MIME types,
> instead of just registering a new optional parameter "forwardshift" for the
> already registered audio/red MIME type. Handling of these 2 new MIME types
> without the "forwardshift" parameter seems to be identical to the handling of
> audio/red.

I have discussed this discuss with Peter and clarified that there is one
actual difference between the two approaches.

Where using new mime types results in that one handles this as two
independent media formats. Thus requiring two different payload types
and negotiating them independently. And these two payload types is in
fact resulting to a doubling of the number of payload types required in
relation to the combination of primary secondary. This as each payload
type only can carry one specific combination of redundancy.

Using a optional parameter in the existing types has the result that one
uses only one payload type and in a negotiation context, like SDP
offer/answer one will use forward redundancy if both peers acknowledge
the optional parameter, and if the other doesn't understand one gets
automatic downgrade to RFC 2198 behavior. If this is the desired
behavior my small concern is how well the implementations handle new
optional parameters. They should but I have no knowledge how well people
implements that handling.

So the question to the WG is what behavior is really desired here?

Please provide any feedback before the 2nd of June.


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVM
Ericsson AB                | Phone  +46 10 7148287
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SE-164 80 Stockholm, Sweden| mailto: magnus.westerlund@ericsson.com