[j-nsp] Packet retransmissions

[dave o'leary]

At 01:45 PM 4/5/2005 +0530, Ramesh Babu Koduru wrote:

>I am using sniffer at receiving end and finding retransmissions at
>receiving end.
>These re transmission packets are visible even when I am doing simple
>ftp from source to destination eventhough I am not sure what's causing
>these re transmissions
>The frequency of re transmission is 10-15mins ...

Do you mean that one packet is retransmitted every 10-15 minutes?

>This MPLS network is an Inter continental network ( ie from India to
>USA) and the RTT b/w source and destination is 290msec ....
>Are these re transmissions on such a long haul network are very common?
>If so ..what could be the main reasons for such re transmissions????

What is the variation in RTT?  Does it move around a lot?
If so, perhaps this is causing TCP timeouts and retransmissions.

                                         dave


>Thanks
>Ramesh babu
>
> >Hi All ,
> >
> >We are testing one broadcast video application on IP MPLS network
> >RTT between Video source & receiver is 290msec . Basically we are
> >transporting multiple TV Channels on MPLS network and trying to watch
> >the quality at other end..........but unfortunately we see occasional
> >video freezes at receiving end  and but there is no packet loss on the
> >network .When I put sniffer to observe packet patterns , I observed
>that
> >there are packet  re transmissions on the network .Can any one here has
> >experienced this kind of problem ? What could be the reason for packet
> >retransmissions while I am not seeing any kind of packet loss on the
> >network??
>
>I'm not sure what the answer to your problem is, but here are a few
>additional questions or things you could try to troubleshoot the
>problem:
>
>I assume that the retransmissions are coming from the video source?
>
>Are you using the sniffer at the receiving end and seeing duplicate
>packets?  Or do you have the sniffer at the transmit end and see
>duplicate packets coming direclty from the source?
>
>What transport layer is the application using?  Is there an application
>layer timer that is triggering a retransmit based on a timeout?
>
>How far apart (in time) are the duplicate packets?
>
>                                                  dave