pvaneynd: (Default)
My wife has a laptop running Vista because she wanted to try out the operating system before having to decide on using it at work.

I called her various names because of it, but that didn't help :-).

So we have this setup with an SMC wireless router/AP talking to a Cisco 837 router that does the internet part. Upstairs we have a 'server' that is connected via Powerline IP-over-power, downstairs we have the Dreambox that is connected via a normal Cat5 connection.

In the last few days my wife complained that it was very slow to download media from Frost. Working at TAC having a network problem at home is almost a personal offence :-) so I decide to take a look and I find using iperf the following speeds:

frost (debian) --cat5--> sharrow (debian): 35 Mbit/sec
frost (debian) ---WL-cat5-> sharrow (debian): 18 Mbit/sec
sharrow (debian) ---WL-cat5-> frost (debian): 18 Mbit/sec
sharrow (debian) --cat5---> frost (debian): 35 Mbit/sec
frost (debian) ---WL---> martha-jones (vista): 0.2 Mbit/sec
sharrow (debian) ---WL---> martha-jones (vista): 12 Mbit/sec
sharrow (debian) ---cat5-SMC-WL--> martha-jones (vista): 6 Mbit/sec
martha-jones (vista) --WL-cat5-> frost (debian): 18 Mbit/sec
martha-jones (vista) --WL--> sharrow (debian): 18 Mbit/sec
martha-jones (vista) --WL-cat5-> sharrow (debian): 18 Mbit/sec

This made no sense at all. The speed halved going from a WL->WL to a WL->cat5 connection but only in one direction!

So having isolated the problem to the Vista machine I started looking round and I found a note saying that running netsh interface tcp set global autotuninglevel=disabled in an 'Administrator' cmd window will fix the problem.

Now I'm very weary of changing the TCP/IP options of the operating system. In most cases the 'tips' you see flying round the internet have no meaning at all and sometimes make the situation worse rather then better.

However I did find this on a Microsoft Technet site.... Hmm

So in the end I try it and modify the setting, disconnect and reconnect to the wireless and:

frost (debian) ---WL---> martha-jones (vista): 18 Mbit/sec
sharrow (debian) ---WL---> martha-jones (vista): 18 Mbit/sec
sharrow (debian) ---cat5-SMC-WL--> martha-jones (vista): 18 Mbit/sec

Aah, finally I could tune Vista so that it has the same speed as an untuned Debian machine. I only took me 2 evenings worth of work...


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