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Having erratic network speeds and have come to the end of ideas for troubleshooting. Basically I have a wired connection that when downloading files starts off slow and slowly builds speed then will suddenly die at that point it will start to speed up again and then die. This just keeps happening until the connection gives up (goes to zero and stays) or the file is downloaded. Watching the network graph looks almost like a heart monitor with its rises and drops.

The system is an MSI P6N NForce board with built in NVidia gigabyte ethernet card. The problem happens on Windows Vista and Windows 7 (RC1) but works fine when XP is used. I also have tried installing a different network card (DLINK PCI 10/100) and see the same problem.

Things I have tried...
- Turning off receive side scaling, flow control, congestion providers and a few other tcp stack settings available via "netsh"
- different cable
- different router
- reinstall both Win7 and Vista
- Microsoft provided drivers and supplied drivers both for the (Dlink and Nvidia cards)

Has anyone seen this sort of thing before? Is there anything else to try before I pull my hair out? The only thing that works is installing XP then everything runs like a champ at full speed with a solid connection.

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This screams of bad drivers for Vista and Windows 7. –  user3463 Oct 21 '09 at 12:43
    
@Randolph - it does sound like a driver problem but I think it's unlikely that the same problem is shared by the Microsoft, D-Link and Nvidia drivers. –  Dave Webb Oct 21 '09 at 13:03

4 Answers 4

up vote 3 down vote accepted

Since everything works fine with XP and you've tried multiple routers we can probably rule out problems on the network.

Again, since it works fine with XP and you've tried two different network cards it's not going to be hardware problem.

Assuming you're installing the same firewall on XP, Vista and Windows 7 it has to be something about the OS itself.

Vista and Windows 7 do have a new IP stack. The only thing I can't think of to try to make them more like XP is to disable IPv6.

You can disable IPv6 either on each adapter or do it system-wide. The latter is probably the choice here. Here's a Microsoft Knowledge Base entry telling you how to do it.

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I have tried disabling IPv6 in Windows7 while I was troubleshooting there but not yet in Vista. I will give it a try in Vista and let you know. –  Matt Oct 21 '09 at 13:13
    
Following the links direction seems to have worked in Vista. I will be reinstalling Win7 later and try it there as well. Turning off IPv6 via the registry (your suggestion) must do something different then using the netsh commands most people recommend. –  Matt Oct 21 '09 at 23:31
    
Followup to Win7. Found it was actually a combination of "netsh interface tcp set global autotuning=disabled" and disabling IPv6. Thanks for all the help, maybe this questions will help someone else in the future. –  Matt Oct 22 '09 at 0:44

I can suggest 3 things:

1) Disable vista's auto-tuning
netsh interface tcp set global autotuninglevel=disabled

2) Disable windows outbound firewall.
Goto control Panel->Administrator tools->Local Security Policy->firewall).
Setup your profile with a new outbound allow all rule.

3) Disable "outbound filtering" on your Anti-virus and try. If it does not work, disable AV altogether.

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Similar suggestion as Dave Webb posted. I have under windows 7 and vista tried disabling autotuning and removed my AV/Firewall software but have not tried to disable the windows firewall yet. I will give this a try when I get a chance. –  Matt Oct 21 '09 at 19:50

If the advice given by Dave Webb doesn't work, the problem is probably on the side of your ISP.

I would suggest in that case to call your ISP's support. They have the tools to test your line from the other side.

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What you are seeing is the normal behavior of a TCP/IP network with only one flow travelling across it. Look at this PDF for an example of TCP's sawtooth behavior. There may not be a whole lot that you can do about this because it indicates congestion in the network which is what triggers the downswings.

For more information on TCP behavior try Googling with TCP sawtooth and you will find lots of material about it.

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This does sounds feasible as we share the network with other people (rural wireless connection) but the issue is not present on this same computer when running XP or a different separate machine while running XP. –  Matt Oct 21 '09 at 19:48

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