We are having a issue with a client not being about to access a server. I don’t see a packet size large then 1518 going across the network, we think that may be the issue, we are seeing RST ACK and Retransmissions together I am not sure what that means, can anyone tell me what is retransmitting and why looking at the trace? asked 13 Apr '13, 17:08  Ernest Johnson edited 14 Apr '13, 14:42  grahamb ♦ |
One Answer:
The net MTU size along the route is only 1460 bytes as the client's SYN packet offers a 'reduced' MSS value of 1420 bytes. In the reverse direction the server's MSS value obviously doesn't get reduced and the client attempts to send a full packet but this doesn't arrive. Path MTU discovery seems to fail as the client finally retransmits with a tcp.len of 536 but this packet gets a reset from the server - probably coming in too late. The solution to this is have the router/fw adjust the server's MSS value to 1420 as it flows to the client. You might want to reduce your mtu size to 1460 as a circumvention. BTW: Your largest outbound packets have an ip.len of 576 which is the default mtu size. Windows uses this when you disable PMTUD at the server. answered 14 Apr '13, 04:27  mrEEde2 edited 14 Apr '13, 08:53 |
Thank You ver much
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that was the problem, we remover the device that was changing the MSS the client end