[MMUSIC] draft-ietf-mmusic-rtsp-nat-14 review

Ari Keranen <ari.keranen@nomadiclab.com> Wed, 05 December 2012 21:22 UTC

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Date: Wed, 05 Dec 2012 23:22:04 +0200
From: Ari Keranen <ari.keranen@nomadiclab.com>
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Subject: [MMUSIC] draft-ietf-mmusic-rtsp-nat-14 review
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I reviewed the draft-ietf-mmusic-rtsp-nat-14 and I think the document is 
in pretty good shape and ready to move forward. Some (mostly editorial) 
comments to consider:

3.  Solution Overview

         The client then installs the STUN servers on each of
         the local candidates transport addresses it has gathered

I would rather say "The client then prepares to act as a STUN server on 
each [...]"

         If the server has a public
         IP address, then a single candidate per address family

In some cases (e.g., certain ISPs, I've heard) even "public" IP address 
does not mean you're not behind a NAT. Maybe it's better to say here "If 
the server is not behind a NAT". Same issue in step 8.

         If the server has a public IP address with a single candidate
         per media stream, component and address family, then the server
         may be configured to not initiate connectivity checks.

This is the "ICE-RTSP", right? Maybe one (small) subsection defining 
this "feature" would make sense. Now it's a bit trickled around in this 
section, sec 4.8.1, 5.4, etc. For someone not familiar with ICE-RTSP, it 
looks like you're talking about ICE lite.

    the NAT need to be refreshed by the client to server traffic provided
    by the STUN keep-alive.

s/keep-alive/keep-alive mechanism/ (or messages).
Also in section 5.11.

5.7.  Client to Server ICE Connectivity Check

    The client receives the SETUP response and learns the candidate
    address to use for the connectivity checks.

s/address/addresses/ (right?)

    Aggressive nomination SHALL be used with RTSP.  This doesn't have the
    negative impact that it has in offer/answer as media playing only
    starts after issuing a PLAY request.

But it does have the downside of possibly selecting a lower-priority 
pair due to single dropped (e.g., due to congestion) connectivity check 
message for a higher priority pair. That said, probably SHALL is 
appropriate here, just wanted to make sure the implications are understood.

5.12.  Re-SETUP

    If the client decides to change any parameters related to the media
    stream setup

Could clarify (again) here that we talk about ICE parameters.