You are here

win764sp1 tcp rwin scaling factor

So thanks to this site ( ) and the smart guy behind it ( Jerry Jongerius ) I truly now believe the only way to monkey with the windows 7 ( 64-bit, service pack 1 ) tcp receive window ( aka RWIN ) is through the rather ambiguously named "heuristics" setting in netsh. Basically, as hopefully the embedded album below will illustrate, because of the decrepit way internet explorer ( 6, was it? ) classified your network security zones rather coarsley ( and, hilariously ) into public, private, and I think come ie 7 it was "work" anything that is regarded as "public" aka the internet has a small RWIN ( lord knows why that decision was made ) of a scaling factor of just 4. The only way to increase that scaling factor is to disable the heuristics ( well I should say the only way that I 've found, I'd like to poke around and see if I can leave the heuristcs ( WHAT DOES THAT MEAN??? ) turned on and just adjust the "public" part of it. Anyway, so in wireshark, looking at the window scale options in the SYN packet from my PC to a download server (happends to be in Washington DC ) I can see the TEENSY WEENSY little scale factor when heuristics are on, and then, when I turn the big "H" off, I can see a much more healthy scale factor of 256. Check it out here in the album, hope it embeds properly: