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

Ari Keranen <> Tue, 18 December 2012 12:43 UTC

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Date: Tue, 18 Dec 2012 14:43:08 +0200
From: Ari Keranen <>
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Subject: Re: [MMUSIC] draft-ietf-mmusic-rtsp-nat-14 review
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On 12/17/12 6:07 PM, Magnus Westerlund wrote:
> On 2012-12-17 16:36, Ari Keranen wrote:
>> On 12/6/12 5:03 PM, Magnus Westerlund wrote:
>>> On 2012-12-05 22:22, Ari Keranen wrote:
>>>>      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.
>>> Yes, but with ICE-RTSP you will retransmit the higher priority also,
>>> thus if that works and you get a response that alternative is nominated
>>> and will be used. But we probably should clarify what it means when
>>> multiple candidate pairs are nominated, and in worse case the server
>>> will use different paths for different media streams.
>> According to ICE RFC, if multiple pairs end up nominated due to
>> aggressive nomination, the highest priority one will be used (you get
>> some transient behavior).
>> But do you mean that you will keep retransmitting on a higher priority
>> pair even if a lower priority pair has been (aggressively) selected and
>> all check lists are in Completed state?
> I guess this needs to be expanded a bit. What I mean is that if due to
> some reason one get a lower prioritized pair to respond and then get an
> answer from the more prioritized then it actually makes sense to unlock
> the full checklist for the more prioritized and let it run to completion
> prior to sending the PLAY request.

By unlocking checklist, do you mean moving it from Completed back to 
Running state and continuing all running checks (until when)? And in the 
case you mention above, both candidates are in the same check list, right?

Anyway, it would be good to clarify this.