At many TechEds this year I’ve presented information about the new TCP/IP stack in Windows Vista. One of the important advances is its automatic performance tuning. With some of the early pre-release builds of Windows Vista, people were reporting problems with public Internet connections, most notably in hotels. Some of the routers used in hotels don’t properly implement the specifications for receive window tuning; the symptom looks like failed DNS requests when trying to browse the Web.
We made some changes to the stack and to Internet Explorer to detect non-conforming gateways and adjust accordingly. And indeed, I’ve seen the problem pretty much disappear. However, the gateway in a hotel I visited in South Africa still exhibited the problem, and when I disabled the auto-tuning Windows could finally connect.
I suspect that most of you won’t encounter this using the RTM build. If, however, on rare occasion you do, here is the command you can issue to disable automatic tuning:
netsh interface tcp set global autotuninglevel=disabled
You can abbreviate netsh commands to the first three letters like this:
netsh int tcp set glo aut=dis
Be sure to re-enable the setting when you aren’t on the hotel’s network:
netsh interface tcp set global autotuninglevel=normal
Or, using the shortened method:
netsh int tcp set glo aut=nor