Re: [AVT] Comments on draft-ietf-avt-rfc2793bis-01

--> Magnus Westerlund <magnus.westerlund@ericsson.com> writes:
> Hi Gunnar and Paul,
> 
> Here is my comments on the payload format.
...
> 12. In regards to the robustness options. As we now have available 
> mechanism to report packet losses, RFC 3611, but probably more important 
> draft-ietf-avt-rtcp-feedback and its NACK format, there is now 
> possibilities to do reactive repairs. I think the possibility should at 
> least be mentioned, or if it doesn't work, that should be motivated. 
> Please investigate this.

Unless specified otherwise, it should be assumed that the standard, payload
format independent, repair schemes can be used with any new payload format.
I don't see any need to list them specially here.

> 14. Section 6.3: The RED SDP examples. Why does on have a=fmtp lines 
> like this? To my understanding of the pt list it should only contain a 
> single 98. This is either a bug here, or problem in the text/red
> document.

The SDP fragments such as

       m=text 11000 RTP/AVP 98 100
       a=rtpmap:98 t140/1000
       a=rtpmap:100 red/1000
       a=fmtp:100 98/98

appear to be correct. The "a=fmtp:100 98/98" line indicates that both
primary and redundant coding use payload type 98. 

> 15. Section 7: I think the security section can be improved:
> - Separate the three main issues, confidentiality, integrity, and source 
> authentication. They are different, and have different severity and 
> attacks, and different counters.
> - The section should give recommendations to mechanism that allows one 
> to counter these problems. For the two first SRTP works very well. For 
> the last it provides some properties that can be used to accomplish 
> that, combined with the signalling.
> So please expand this.

Note that this is recommendations, rather than "MUST" requirements, since
SRTP is not appropriate in all cases.

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

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