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Our site is connect to the internet by a pair of lines which currently have a significant difference in latency. We have a suspicion that when we enable 'downstream bonding' on these lines (i.e. our ISP distributes incoming packets across both lines) we're suffering a major loss of TCP/IP performance because of packet-reordering problems.

We're going to get the latency imbalance fixed, but in the meantime, is there any way on Windows (7RC on this machine, but general advice for XP/2003/Vista is fine) to either A. increase the number of packets which can be reordered and/or B. determine whether or not the TCP layer of the stack is actually discarding lots of out of order segments.

It seems that this is something the TCP layer could easily count, but I can't see anything on perfmon/netstat which looks useful.

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up vote 2 down vote accepted

Have you tried Wireshark to actually monitor the traffic?

In particular:

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+1. Specifically, the filter 'tcp.analysis.flags' will show you anything that indicates undesirable TCP behaviour. (Retransmissions, out of order packets, duplicate ACKs). – Murali Suriar May 15 '09 at 13:17

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