Subject: Re: [MMUSIC] I-D ACTION:draft-ietf-mmusic-media-loopback-00.txt

From: Colin Perkins <[email-masked]>
Date: Sat, 8 Jan 2005 19:59:24 +0000

On 28 Dec 2004, at 20:51, [email-masked] wrote:
> 	Title		: An Extension to the Session Description Protocol
> 			  (SDP) for Media Loopback
> 	Author(s)	: K. Hedayat, et al.
> 	Filename	: draft-ietf-mmusic-media-loopback-00.txt
> 	Pages		: 14
> 	Date		: 2004-12-28

I have some comments on this draft:

I'd like to see more motivation for why rtp-pkt-loopback is useful. I 
can see why rtp-media-loopback would work, since it returns the media 
as presented to the remote user, but the benefits of rtp-pkt-loopback 
are less clear, especially since the receiver must regenerate the RTP 
sequence number when it loops back the media, making it difficult to 
detect lost packets.

The requirements on use of RTCP XR in section 7 are, I believe, too 
strong. This is because not all applications support voice, or 
necessarily wish to implement RTCP XR. I would recommend changing 
section 7 to state that RTCP MUST be implemented, and to note that RTCP 
XR MAY be used in addition (with an explanation of why it would be 
beneficial to implement RTCP XR, rather than a normative "SHOULD" 
strength requirement to do so).

I don't believe the security considerations are adequate. The draft 
needs to discuss the potential for DoS attacks in more detail, explain 
how the use of authentication will prevent such attacks, and provide 
recommendations of how to perform authentication such that 
interoperable implementations can be built. I'd also expect there to be 
some greater discussion of the privacy implications, and a 
recommendation that end points either MUST NOT loopback media without a 
users knowledge, or MUST allow the user to disable loopback.

IANA considerations is inaccurate, since the IANA must register certain 
new SDP attributes.

Please also fix the following nits:

idnits 1.49 (16 Nov 2004)

draft-ietf-mmusic-media-loopback-00.txt:

   Checking conformance with RFC 3667/3668 boilerplate...
   The document seems to lack an RFC 3667 Section 5.1 IPR Disclosure 
Acknowledgement
   -- however, there's a paragraph with a matching beginning. 
Boilerplate error?
   The document seems to lack an RFC 3667 Section 5.4 Copyright Notice
   -- however, there's a paragraph with a matching beginning. 
Boilerplate error?
   There are 1 instances of lines with control characters in the 
document.

   Warnings:
     There are 1 instances of lines with hyphenated line breaks in the 
document.

Colin

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