Windows Live Messenger fails to connect in Windows Vista
Quoting: http://michitsch.spaces.live.com/blog/cns!24F6FD85048B600D!107.entry
And here is a solution, that worked perfectly for me, and several of my clients clients.
Drop to a command prompt and run: netsh interface tcp set global autotuninglevel=disabled
If the command returns this response, “Set global command failed on IPv4 The requested operation requires elevation”, then you need to do this: Click start (windows symbol), Accessories, right click on “Command Prompt”, then choose “Run as Administrator”, then try the netsh command (above) again.
Because this command failed when I was logged on as Administrator, I say again…
If the command returns this response, “Set global command failed on IPv4 The requested operation requires elevation”, then you need to do this: Click start (windows symbol), Accessories, right click on “Command Prompt”, then choose “Run as Administrator”, then try the netsh command (above) again.
EXPLANATION:
The Microsoft Windows Vista OS enables the TCP Window Scaling option by default (previous Windows OSes had this option disabled). The TCP Window Scaling option is described in RFC 1323 (TCP Extensions for High Performance), and allows for the device to advertise a receive window larger than 65 K than TCP originally specified. This is useful in the higher speed networks of today, where more data can be outstanding on the wire before it is acknowledged. This slow performance, or dropped TCP connections is caused by some versions of Cisco IOS® Firewall software not supporting the TCP Window Scaling option. This causes it to have a much smaller TCP window than the endpoints actually have. This causes the Cisco IOS router that runs the IOS Firewall feature set to drop packets that it believes are outside the TCP window, but which really are not.
So, through many firewalls, many protocals fall apart.