Subject: Re: [AVT] Merge the two retransmission drafts

From: [email-masked]
Date: Fri, 5 Jul 2002 14:52:36 -0500

I see no need and little use for two very similar protocols / mechanisms.
I agree completely that the two should be merged into one.

Jim

Magnus Westerlund <[email-masked]>@ietf.org on
07/05/2002 06:34:15 AM

Sent by:  [email-masked]

To:   IETF AVT WG <[email-masked]>
cc:
Subject:  [AVT] Merge the two retransmission drafts

Hi,

This mail is arguing for the merger of  the two retransmission drafts
draft-ietf-avt-rtp-selret-05.txt and
draft-ietf-avt-rtp-retransmission-02.txt. I do believe that there is
significant advantages of merging the two proposals.

First, the two proposed solutions for retransmission are very similar.
The only real difference is if the retransmitted packets are done in the
original stream or in a new session. Otherwise there is a number of
smaller issues regarding how the sever and client should behave. This
would benefit from having a single document explaining how they should
behave. If there are differences that are necessary for different use
cases these could clearly be presented and signaling introduced. This
would help future implementors from having to read two documents that
are slightly contradicting and form there own idea.

Secondly, the selective retransmission draft is actually describing two
mechanisms that can be used independently of each other. The draft
describes how to do actual retransmissions with the help of the RTX
format, this functionality does also exist in the retransmission draft.
However the mechanism for giving the client prioritization information
so that it can better utilize a narrow back-channel at some cost in the
forward channel is not present. By merging the two draft the
retransmission transport mechanism in Leon's draft can be used together
with SEL payloads. This could be solved by splitting out the mechanism
for selective retransmissions request, however I do believe that this
would make an overview of the possible solutions harder.

Third, the two retransmission payload formats are very similar. Actually
the selective retransmission drafts format can be seen as a superset of
the other drafts format. So I would argue that the RTX payload formats
should be common between the two solutions. This would be very simpler
if the two solutions is contained in the same draft.

Fourth, the SDP signaling part for how to use retransmission are
immature for both proposals. I strongly believe that this would be
simpler to align and verify if merged into one document. There are a
number of possible use cases of either of the solutions that needs to
possible to distinguish. These may more simply be missed when having two
documents.

Comments?

Regards

Magnus Westerlund

Multimedia Technologies, Ericsson Research ERA/TVA/A
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Ericsson AB                | Phone +46 8 4048287
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S-164 80 Stockholm, Sweden | mailto: [email-masked]

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Audio/Video Transport Working Group
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_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt