TCP Window Size

[nohbdy]

I'm currently running s3sync on Windows 2008 (not within cygwin) but am experiencing rather slow upload speeds to S3.  A packet trace shows that my TCP Window size never goes above 64K.  Other applications uploading to S3 that have higher TCP Window sizes are getting the full bandwidth available.

Anyone been able to successfully increase the TCP Window size in s3sync?

[ferrix]

Wow, is that something you can even *do* in ruby I wonder?

[nohbdy]

Haha, great question.  I was trying to figure that out myself, but I'm no TCP programming expert.

I'm a little confused because I didn't think that would be something you should ever have to do.  I thought the OS was supposed to handle these things for you.  It obviously isn't doing that though.

[ferrix]

Yeah I think it's an OS-level thing. 

[nohbdy]

Hmm, I was right, the OS should scale the TCP window size.  But, it appears that the send buffer isn't large enough to allow for the window size to scale up.  You can adjust the send buffer through normal Winsock API calls.  Now, the question is, how do you do that in ruby?

Surely I'm not the only one that has tried/needed high speed (ie: > 5 mbit) uploads via s3sync.