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szkwg_89687's avatar
szkwg_89687
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Oct 08, 2012

tcp profile for heavy packet loss

at this moment my ltm is using 'High Speed'. when there are heavy packet loss, the retransmission timeout goes to 32 seconds, and sometimes goes to 64 seconds. And this causes a whole transaction tak...
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szkwg_89687's avatar
szkwg_89687
Icon for Nimbostratus rankNimbostratus
Oct 18, 2012
"Maximum Segment Retransmissions" was kept at 8 times. when keepalive is set to 8 seconds, the times of retransmission seemed to be cut to 3 times (i think so, it is a bit hard to simulate packet drop in lab env ). As the app is web-based, it is not easy to tune the app to send another request. Apologize I did not make the situation more clear. Keepalive is chosen because packet loss could be bidirectional, i.e., data packets and some of its ack, I would like to have keepalive packets flowing to have acknowledge number showing up.

 

 

Under normal circumstance, RTT is 40ms, data to transfer is about 160KB. basically it is a packet loss burst, within one window several packets got dropped. Yes, retransmissions are timeout based. at first, i was thinking to use new Reno, but it seems the interval of retransmission still went up to 32 sec or 64sec. As the interval turns to so large, I did not notice/calculate smoothed RTT.

 

 

I will learn more about wom-tcp-wan-optimized. tcpdump part, I will try to replace ip and upload.