I currently have a data center connected to two remote locations via MPLS - 2M and 6M respectively. The 2M connection (to Asia from the US) has about 300ms of latency and when transferring between clients (XP, 2003 Server) and server (2003 Server) a single flow won't exceed .65 Mbps.
I can get a very nice connection via FTP that fills up pretty much the entire 2 Mbps with a single threaded FTP connection but CIFS or whatever else TCP based seems to be gimped horribly.
It's been suggested that this is a TCP window size issue but when referring to this to change the window size to 64K (or larger, I've tried a range of window sizes) it doesn't change my transfer speed at all. I've peeked at Network Monitor to see what window sizes I'm negotiating and it's reporting that if I set it to 64K it's really negotiating 64K and so on.
I don't really have much experience with any of this insanity so was hoping someone might have some insight into what I'm missing or some things to consider.