I need to minimize latency for sending moderate-sized messages (~100kb) from a Windows Server 2008 R2 to another machine with the same OS.
Studying wireshark logs and looking at tcp graphs shows that more than half the latency is explained by tcp slow start: the initial window size is so small that by the time it increases to a value sufficient to saturate the network bandwidth, the message is already over.
Googling told me that in pre-Vista, it was possible to manually set the TCP window size, but in Vista there's "auto tuning" for that.
Is it still possible to somehow, perhaps even programmatically, set this parameter for new tcp connections?
Best Answer
Yes, it's possible to adjust the Initial Congestion Window.
I've been looking at it from a web performance PoV, have a look at this blog post Increasing the TCP Initial Congestion Window on Windows 2008 Server R2