Re: [rtcweb] STUN for keep-alive

Randell Jesup <randell-ietf@jesup.org> Wed, 14 September 2011 15:02 UTC

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Date: Wed, 14 Sep 2011 08:04:26 -0700
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Subject: Re: [rtcweb] STUN for keep-alive
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On 9/14/2011 7:45 AM, Jonathan Lennox wrote:
> Christer Holmberg writes:
>> Well, it depends on the amount of outgoing media traffic, but in cases where you only receive media you would still need to send keep-alives.
> Remember, RTCWeb is (probably) mandating RTP/RTCP mux.  I'd need to do some math to be certain, but I'm pretty sure that in almost all normal circumstances, the RTCP regular reporting interval should be significantly smaller than the STUN keepalive interval.

Agreed; I think it would require a bizarre session setup (RR=0) to force 
the RTCP interval out far enough to cause problems.  (Don't forget to 
include the +- 50% in the calculation.)

RFC 3556:

       o  If RR is zero, then the proportion of participants that are
          senders can never be greater than RS/(RS+RR), and therefore
          non-senders never get any RTCP bandwidth independent of the
          number of senders.


Obviously, RR values near 0 could also cause a problem.  A statement 
about not using RR values that would result in RTCP intervals greater 
than N should be enough I think.

BTW: Have we mandated that RTP & RTCP be muxed always to all 
destinations, or that it must be supported and offered?  If you're 
talking to a legacy device that doesn't mux, what happens?

-- 
Randell Jesup
randell-ietf@jesup.org