Subject: [AVT] Reg: practical upper bound on RTCP Interval

From: "Siddhartha Gandhi" <[email-masked]>
Date: Thu, 9 Feb 2006 17:29:55 -0600

Just wondering, how do we calculate the practical upper bound on rtcp time
interval ( RTI ) that is returned by the rtcp_interval() routine of RFC
3550, section A.7 ?

There is the one such method in the paper, "Timer Reconsideration for
Enhanced RTP Scalability". But that seems to be true only if taken with the
bounds mentioned.

Only place where it can cause problems, if not taken care of is, when RTI
becomes large enough to exceed the registration time of the participant.

The lower bound as  is evident, is 2.5 sec if this is the first rtcp packet;
5 sec otherwise.

Note: There seems to be a minor typo on page 74 of RFC 3550, in void
OnReceive(). Instead of double *tp, tc, tn it should be, time_tp *tp, tc,
tn.

- Siddhartha

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Colin Perkins <[email-masked]>
Date: Fri, 10 Feb 2006 10:42:49 +0000

On 9 Feb 2006, at 23:29, Siddhartha Gandhi wrote:
> Just wondering, how do we calculate the practical upper bound on  
> rtcp time interval ( RTI ) that is returned by the rtcp_interval()  
> routine of RFC 3550, section A.7 ?
>
> There is the one such method in the paper, “Timer Reconsideration  
> for Enhanced RTP Scalability”. But that seems to be true only if  
> taken with the bounds mentioned.
>
>
>
> Only place where it can cause problems, if not taken care of is,  
> when RTI becomes large enough to exceed the registration time of  
> the participant.

The interval varies depending on the session bandwidth and number of  
participants. If you can bound the number of participants in the  
session, that will allow you to calculate the upper bound for the  
average RTCP interval; if you can't bound the number of participants,  
you can't bound the interval.

> The lower bound as  is evident, is 2.5 sec if this is the first  
> rtcp packet; 5 sec otherwise.

All +/- 50% randomisation, of course.

Colin