Subject: [clue] The requirements in draft-lennox-clue-rtp-usage-04

From: "Roni Even" <[email-masked]>
Date: Tue, 28 Aug 2012 12:57:02 +0200

I have some comments on the requirements in section 9 of
draft-lennox-clue-rtp-usage-04.

1.       The first requirement should be that any solution must work with
existing protocols and should not require duplication of information sent
using existing protocol.

2.       I am not sure if media-4 and media-5 are requirements or
description of the flow.

3.       In media-6 the term "immediately" is vague,  I assume that the
mapping should be available before a new source is received. I think this is
nice to have but we do not have a requirement for reliable delivery, maybe
one should be added or is this a requirement for reliable delivery.

4.       In media-6 the sentence "and thus that any previous source is no
longer being mapped to that switched capture." is not clear and I am not
sure if it is true, I think it can be deleted since it does not provide
value.

5.       In Media-8 the sentence "It must be possible for a source to move
among switched captures without requiring a refresh of decoder state (e.g.,
for video, a fresh I-frame), when this is unnecessary." I think that instead
of saying "when this is unnecessary" is should say "if the receiver support
this funcationality". 

6.       In Media -8 the sentence "However, it must also be possible for a
receiver to indicate when a refresh of decoder state is in fact necessary".
Is this a CLUE or RTP mapping requirement? Should CLUE provide means for it,
otherwise I do not see any point in having this sentence since this is
current practice for switching and there is no intention to change it.

7.       In Media-9 the sentence "it should be  possible for a sender to
send only one copy of the source". This is true only if the receiver
supports it so suggest adding to the end of the sentence "if the receiver
supports it". Note that this requirement and requirement 8 require new
capability negotiation.

8.       In media 10 "media flows should, as much as possible, look and
behave like currently-defined usages of existing protocols". Is this a
suggestion to change RTP? If not what is this requirement about the media
flow?

9.       I do not think that Media- 11 is correct. The processing depends on
the topology chosen by the implementer. So if you want such requirement it
should say per topology "to have lower burden per topology". The selection
of topologies has to do with application decision like source hiding,
central decision preferences.

10.   I do not think that requirement 12 is adding something new which is
not part of RTP/RTCP or is there some new information needed?

BTW: the requirements are discussed in section 5 of
draft-even-clue-rtp-mapping-03

Roni Even