Subject: Re: [AVT] I-D Action:draft-ietf-avt-rtcp-non-compound-06.txt

From: Colin Perkins <[email-masked]>
Date: Thu, 7 Aug 2008 16:19:18 +0100

On 7 Jul 2008, at 11:30, [email-masked] wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts  
> directories.
> This draft is a work item of the Audio/Video Transport Working  
> Group of the IETF.
>
>
> 	Title           : Support for Reduced-Size RTCP, Opportunities and  
> Consequences
> 	Author(s)       : I. Johansson, M. Westerlund
> 	Filename        : draft-ietf-avt-rtcp-non-compound-06.txt
> 	Pages           : 17
> 	Date            : 2008-07-07

This is generally in very good shape. My comments are almost entirely  
editorial, but there are a couple of technical points:

Which other RFCs does this update? I assume RFCs 3550, 3711, and  
4585, but these need to be listed in the header, abstract, and  
introduction.

The introduction points to sections 3.1, 3.2 and 3.4. For  
consistency, it should also reference section 3.3.

The last paragraph of the introduction should probably also reference  
section 4.

In Section 2, the definition of Lower Level Packet ends "...in 3 in  
[RFC3550]". Is the word "section" missing?

Section 3.4.3 need to be explicit that this is a change to the rules  
in RFC 3711, and requires updated implementations.

Sections 4 and 4.1 need to clearly define which profiles this can be  
used with this extension. The current text allows this extension to  
be used with RTP/AVPF, and prohibits its use with RTP/AVP, but what  
about RTP/SAVP and RTP/SAVPF? (presumably the former is prohibited,  
and the latter allowed)

Section 4.2.1 notes that "An algorithm to detect consistent failure  
of delivery of reduced-size RTCP must be used by any application  
using it.  The details of this algorithm is application dependent and  
therefore outside the scope of this document". I don't think this is  
sufficient: the draft must specify for each RTCP packet type, how it  
can be used as a reduced-size message, and how it's reception can be  
detected.

Section 4.2.2 "can become larger than a normal compound RTCP" seems  
odd, since a reduced-size RTCP packets won't contain the SR/RR part,  
and so will be smaller than it would when sent as a compound RTCP  
packet. Do you mean "can become larger than a regularly scheduled  
compound RTCP packet"?

Regards,
-- 
Colin Perkins
http://csperkins.org/

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