Re: [AVT] Reg: Testing RTCP Intervals

[Colin Perkins <csp at csperkins.org>]

On 22 Feb 2006, at 17:27, Siddhartha Gandhi wrote:
> I was looking for a document to test my rtp implementation for RFC  
> 3550 and ran into RFC 3158 which states the following;
>
>       o  the minimum interval is never less than 2 seconds or more  
> than
>          2.5 seconds;
>
>       o  the maximum interval is never more than 7 seconds or less  
> than
>          5.5 seconds;
>
>       o  the average interval is between 4.5 and 5.5 seconds;
>
>       o  the number of intervals between x and x+500ms is less than  
> the
>          number of intervals between x+500ms and x+1s, for any x.
>
> Since the minimum interval is 2.5 (initially) with +/- 50%  
> randomization, we will have time interval in the range[1.25 sec,  
> 3.75 sec] for the participant. Why do we have to bring up the  
> minimum time interval from 1.25 sec to 2 sec ?

The quoted text is from section 2.4.1 of RFC 3158 and is measuring  
the interval between consecutive RTCP packets, when the session  
bandwidth is such that the average reporting interval is 5 seconds.  
Since only the time intervals between pairs of RTCP packets are  
measured, the time before the first RTCP packet is not counted in the  
statistics (hence the lower bounds of 2 seconds).

> Also the maximum interval is governed primarily by the total number  
> of participants. Why do we have to have the upper bound of 7 sec  
> and lower bound of 5.5 sec ?

Because there are only two participants in this testing scenario, and  
the session bandwidth is configured such that the average reporting  
interval is 5 seconds.

Colin

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