Thursday, May 7, 2009

Automatic Vista Speedup with a D-Link DIR-625

note: This article is intended for a technical audience -- you should use caution when modifying a production system -- caveat emptor.

This probably works with the other DIR-6xx models that D-Link sells too, but recently oldfeeb had an issue where his girlfriend's computer (Vista Home Premium) stopped talking wirelessly to the new DIR-625 he'd bought.

He uses Ubuntu, so he saw no difference, but the symptoms on Vista were related to Windows Mail and Internet Explorer refusing to browse, or overly long timeouts.

First up, update Vista for all the recent fixes and reboot -- no luck.

Noticing the cordless phone handset on the wall, I thought: change the wifi channel on the router to something that doesn't conflict with things like cordless 2.4Ghz phones, move channel 5 to channel 11, check.

Reboot Vista, slightly better signal, but the network is still slow -- Google works now, but only after 30 odd seconds, but her mail times out and heavier webpages die a quiet death.

So, using a tip that I found courtesy of Australian Personal Computer magazine some years ago and a bit of Googling, we switched off Vista's 'Autotuning of TCP parameters'.

To do this, you'll first need to open a command prompt as the Administrative User -- which involves:

  1. Go to Start / Run

  2. Type "cmd.exe" into the box provided.

  3. Hold down the Control and Shift keys together -- then -- press [ENTER].

Now, type the following at the prompt:

netsh interface tcp set global autotuning=disabled

Restarted IE7, fired up Google, works flawlessly.

"OK, I thought -- put the Wireless Channel on the router back to 5 (the default)."

We did, rebooted Vista -- Stone, Cold, Silence.

Switched it back to 11, rebooted Vista -- everything's peachy again.

So, sometimes it's not just Vista's fault -- I guess if you're going to buy a Wireless router, you should check what channel ranges are valid for the country you're trying to use the hardware in, before blaming the workstations directly.

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