Ethereal-dev: [Ethereal-dev] Round Trip delay problem

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From: "Szymon Fedor " <szymon.fedor@xxxxxxxxxxxx>
Date: Mon, 24 May 2004 06:49:13 GMT
Hello,

I have a little problem with round trip delay computing and I am not sure if I am doing something wrong or there 
is a bug within ethereal. To calculate the round trip delay I capture the RTCP protocol packets. I read the 
sendind time of the Sender Report and the time of capturing the Receiver Report. Then I calculate the 
difference of them. To get the round trip delay I have to substract from that result  the "Delay since last SR 
timestamp" value. The problem is that Delay is superior than the previous difference, so I will get a negative 
result for the round trip time. That happens for all pairs Sender Report/Receiver Report.
Below is an example of my calculation:

Sender Report sending time: 34.522171 s
Receiver Report reception time: 35.339164 s
Difference=0.816993 s
Delay since last SR timestamp: 54208 which corresponds to 54208/65536=0.8271484375s (the unit of that field 
is 1/65536 s, ref: RFC 1889 ). 
Round trip delay=0.816993-0.8271484375=-0.010155s

Any ideas where is the problem?

Thanks for help
Simon

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