Silly Window Syndrome
[See Stevens, volume 1]
Commonly exhibited by NT4 TCP client stack when sending bulk data.
From a mailing list: "The work-around was to change the tcp_deferred_ack_interval parameter in Solaris 8; this parameter indicates the delay in milliseconds before sending a deferred ACK (the default for windows is 200ms, for Solaris 8 is 100 ms and for most linux distributions 50ms; I set it to 10ms and the file uploads are 10 times faster!).
I believe the new low value of 10ms is OK for LANs (where RTT for TCP packets are less than 10ms) but it may not work for WANs."