When I upload data from DPS (where my tcp implementation is) to windows (an ftp server takes the data there), the windows tcp hangs at times. It happens only at 100 MbpS. Something like 8 megabytes/S get sustained for a few seconds with several retries, then at some point the windows tcp acks only part of the last segment it could take with a window size of
- My tcp retransmits that segment, but windows repeatedly (for many seconds, until I time out) only resends its last ack with the 0 window size. Clearly an error at the windows side - the window must have opened (and the rest its tcp/ip system keep on working), but then two windows systems talking to each other don't lock up in this manner - at least I have not seen it (never researched them in depth). What am I supposed to do? I suspect sending some probing segment of a different size will make the windows side stop repeating its last (probably queued) response. Generally I will manage to fix the issue, what I want to know is how widespread this issue is. Do other people observe it? I am using window scaling, I let windows define the shift factor which IIRC is 3 (ftp DPS client windows server, non-passive mode - the issue occurs on the data connection, obviously). It is not an ethernet buffering issue, my side never sees any "xoff" packets and windows says it has sent none - and they are enabled. Clearly the tcp buffer gets full and things halt; it may even be the ftp server (filezilla). I tried to dramatically increas the server buffer size (it is configurable) to no effect.
Thanks for any insight,
Dimiter
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