Subject: [Sipping] conf: comments on draft-evan-sipping-media-policy-requirements-00

From: "Eric Burger" <[email-masked]>
Date: Thu, 20 Mar 2003 14:43:51 -0500

Requirements in general:
I don't get the subject of the requirements.  Is the subject (in the grammatical sense) CPCP (protocol capabilities), the identified party (the participant or mixer), or something else?

For example in REQ-GP1, is the *participant* the party that MUST be able to specify its own topology?  Here's a nasty result: a company hosts an earnings announcement conference call.  Two analysts create a sidebar and get private communications service paid for by the host.  I don't think the participant MUST be able to specify topology, at all.  Alternately, is the *protocol* the party that MUST be ABLE to specify topologies?

Likewise, in REQ-GP3, does this say that the *protocol* MUST allow the SPECIFICATION of the number of streams, or does this say that the *mixer* must support dynamic active talker sizing?

REQ-GP4 is unrealistic and over the top..

The Security Considerations is VERY light.  It essentially says, "bad things can happen, but we're not going to do anything about it."

I don't understand any of Section 8.  It desperately needs examples.  I'm still not convinced of the need for arbitrarily complex, *participant-driven* topology description and manipulation.

Section 8.1:
What on Earth is LastLoudest?  What is the "audio mix set before the current one"?  Over what time period?  Is this continuous?  How often does it get updated?

Does Not(Qualifier) result in a set?  E.g., in a conference with more than 2 participants, Not(LastLoudest) results in more than one stream.

Section 8.3:
What is the use case for LoudestSpeaker(N), where N != 1?  I would offer that if the use case is, "I will construct a mix of the three loudest talkers by doing 
Mix(LoudestSpeaker(1),LoudestSpeaker(2),LoudestSpeaker(3))", you will have exactly zero implementations.  That is very hard to do.  Moreover, I don't know anyone that is interested in, "Please play for me the 6th loudest speaker."

I would STRONGLY suggest against using numerical table numbers to describe VideoLayout.  That's begging for mistakes an non-interoperable implementations.
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