[Planetlab-users] question about packet loss

[Daekyeong Moon]

Hi,

I'm seeing weird udp loss.
I'm replaying traffic traces from some Internet application.
The replayer is a very simple udp application injecting packets from a  
pcap file according to the packet interval recorded in the file.

Each sender generates at most 50 udp packets per second for 2 minutes,  
and each packet is 300 bytes on average.
So, each sender consumes about 120Kbps, which is not much.

A receiver receives packets from 7 senders (approximately 840Kbps),  
and reports timestamp using SO_TIMESTAMP.
But, I found that the receiver sometimes doesn't receive any packet  
for more than 10 seconds.
(select() call with 10 second timeout also fires.)

Since, the traces don't have such big gap and the receiver receives  
from the 7 senders, this is quite abnormal.
I repeated 200 times with random planet lab nodes in the US, and I  
don't think it's the issue of particular nodes.

I'm just guessing it could be related to the receiver's bandwidth  
limitation.
(e.g. dropping all packets until the next time window if bandwidth  
usage in a certain time window exceeds the Shared BW limit)

Anybody experienced the same issue?


Thanks,

DK