Subject: [AVT] Comments on draft-ietf-avt-rtcp-feedback-02.txt

From: Colin Perkins <[email-masked]>
Date: Wed, 27 Mar 2002 00:04:28 -0500

I've just re-read the RTCP feedback draft. In general it looks pretty good,
but I have a few (mostly editorial) comments:

- Abstract is too long, and reads more like an introduction.  Suggest it
  is rewritten (also remove citations from the abstract, and put them in
  the introduction instead).

- In section 1.1, description of Feedback Threshold is confusing. Suggest
  adding text to note that, before the feedback threshold, immediate mode 
  is used and after it, early feedback mode. Be explicit about the change.
  (section 3.3 explains this clearly, maybe just give a pointer).

- Section 3.1 states that minimal compound RTCP packets "SHOULD be used
  whenever an RTCP feedback message is sent as part of an Early RTCP packet" 
  then says that full compound RTCP feedback packets "MAY also be used to
  send RTCP feedback messages in Immediate Feedback or Early RTCP mode".
  It's not clear when the SHOULD is overridden by the MAY.

- Section 3.4 mentions a variable "g" but doesn't define it? (or do you
  mean item g in the list?)

- End of section 3.4: give an exact formula for deriving the updated tn.

- Section 3.5 "reasonable at the current constellation"? 

- Section 4.2: the "rtcp-fb" attribute is not appropriate for "a=fmtp:",
  which is for codec parameters. 

- When discarding unknown feedback messages, do those messages count
  towards the average RTCP packet size?

- Section 4.2 notes that "<rtcp-fb-id>" parameters "MUST be registered with
  IANA". Accordingly, the IANA considerations section needs to define the
  registry for these parameters.

- Sections 6.2 to 6.4 could define the RTCP message types (i.e. give them
  numbers) which are then to be registered in the IANA considerations section 
  (else the IANA has to go through the draft, and assign numbers).

- End of section 6.3.2.2: is the text "the PictureID is identical to the
  Temporal Reference.." complete?

- Section 6.4 should start "Application specific feedback messages are a 
  special case..."?

- The IANA considerations section should specify which IANA registry the
  new parameters are to be added to, and should define the new registries
  and the rules for adding new parameters to them.

Cheers,
Colin

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