Packets being resent

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Apr 2nd, 2007
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When analysing network traffic between PCs and Cisco 6513 copper blades I am seeing the majority of packets being resent. The analyser is displaying every other packet as lost packet. The cisco blade interfaces are showing no errors. Any suggestions please. Port speeds are fixed at 100 full duplex at both ends.

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didyap Fri, 04/06/2007 - 09:03
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If the packets are resent definitely there should be errors, also could u do a debug and then bring up the debug data

situwayne Fri, 04/06/2007 - 10:55
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excessive retransmissions does not necessary translate into errors. retransmission is part of tcp feature.


For example: host A sent a stream of data to host B. B would have to respond to A with Acknowlegements of receiving data. If A does not receive Ack from B (timer..see RFC below), then A would retransmit thinking that data never arrived.


In your case it sounds pretty bad....every other packet. if possible, sniff traffic from both hosts simultaneously and compare.


this maybe an application issue of pc is over utilized, which unable to respond. or many other possible scenario.


tcpipguide.com is a good free reference to understand how tcp works.


http://www.tcpipguide.com/free/t_TCPSegmentRetransmissionTimersandtheRetransmission.htm


http://www.ietf.org/rfc/rfc2988.txt


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