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I have a specific desktop which seems to have consistently high packet loss and ping regardless of what connection it is using. I'm connecting via wifi and this computer usually has a ping to my router of around 800ms and packet loss of around 20%. I've tried different wireless adapters, and even using the usb tethering on my phone, and they all have the same result.

The computer is running Windows Server 2008 R2 and Arch Linux, and the problem only exists on Windows for usb tethering. I can't test with the wifi adapters on Linux, as there are no drivers for them.

It is also not a locational or hardware problem. My laptop can connect without issue from the same position, either by using its own wireless adapter, a usb adapter which has issues in the desktop but is fine in the laptop, or usb tethering through my phone.

I've tried disabling 11n on my router so I know it's connecting by 11g, and it had the problem, and I tried setting it to 11n and it had the problem.

I've no idea on how to diagnose this. I can't find anything in my network settings which look likely to be the cause.

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1 Answer 1

Many things could be checked:

  • lots of network usage from that host? (use: wireshark )

  • lots of CPU usage resulting in a drop of network packets? (use Sysinternals "Process Monitor")

  • MTU settings: you could have a sub-optimal setting. I'd just do bigger and bigger ping with the "don't fragment" bit set, and see where it starts to break, and figure out then the best MTU setting (which is not the same number as the ping size, because of the ip and tcp headers overhead. Read about it for details). But beware: don't change more than 1 thing, and heavily test each time. You could completely mess up your connection!

  • routes: you may have conflicting things, such as several default gateways, etc, possibly generating unwanted traffic (such as useless duplicated packets).

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I've checked all of these, and none of them seem to be the cause. Network usage is basically 0 and it's still problematic, CPU usage is about 40%, pings have the issue even if I set the size to 100, and I don't have several default gateways. –  Macha Dec 28 '12 at 13:36
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try to borrow a cable and see if, when connecting via cable, the situation is different. This will help pinpoint the real source (wifi card? tcp/ip stack? some hidden thing on the server itself?) –  Olivier Dulac Dec 28 '12 at 13:43
    
Have you tried moving it? You list several other things, but you don't list moving it. If you have not, attempt to place the PC directly adjacent to the wireless router and see if it continues to have the same issue. If it does, you can eliminate wireless signal interference or connectivity...and probably the wireless card since you've already swap tested that. –  George Spiceland Feb 23 at 5:28

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