TCP Window-Full Zero-Window Stall Downloads

[sluk]

I just receive my Windows 7 64-bit laptop and I encountered problems with Internet downloads. I've tried download using IE or Firefox and via the LAN and Wireless adapters and the results are the same - downloads always stuck in the middle at random position and cannot complete. I use Wireshark to capture the network packets and discovered that whenever the download interruption occur there will be TCP Window-Full sent over from the server on the other side and the local adapters respond with TCP Zero-Window then the download stalls. Then I downgrade the machine to Windws XP everything working fine, so I believe this is a Windows 7 related issue, any idea how can this TCP Window-Full /Zero-Window stalls download problems under Windows 7 be resolved?

 

[logicearth]

What antivirus or security software are you running?
Using the latest drivers for your network card?

 

[sluk]

It is a clean install, no application, just chip set, network adapters drivers being installed for the test. Yes, the drivers are most up-to-date

 

[chev65]

I just receive my Windows 7 64-bit laptop and I encountered problems with Internet downloads. I've tried download using IE or Firefox and via the LAN and Wireless adapters and the results are the same - downloads always stuck in the middle at random position and cannot complete. I use Wireshark to capture the network packets and discovered that whenever the download interruption occur there will be TCP Window-Full sent over from the server on the other side and the local adapters respond with TCP Zero-Window then the download stalls. Then I downgrade the machine to Windws XP everything working fine, so I believe this is a Windows 7 related issue, any idea how can this TCP Window-Full /Zero-Window stalls download problems under Windows 7 be resolved?

Hi sluk, what make and model of router are you using?

 

[sluk]

Juinper Netscreen 5 , a very very OLD hardware firewall router.

 

[chev65]

If you can find a fairly recent firmware update that might help although many routers ended support well before Windows 7 was released. There were so many changes to the network stack with Windows 7 that often times old routers will not work without a firmware update.

If the firmware update doesn't work it may be time to upgrade your router.

 

[sluk]

Unfortunately, the router already stop production few years ago. Oh well, maybe I can test local ftp / http kind of file transfer see without involving the router make any different. Already tried Windows Copy/Paste to / from a NAS on the same LAN without any problem.

 

[logicearth]

What probably is going on is your router is messing with TCP Window Scaling, common among old network gear.
TCP Window Scaling is very important to get the most out of your high-speed network/internet.
Without it a packet can only hold 65,535 bytes, but with it can reach 1 Gigabyte.

Transmission Control Protocol - Wikipedia, the free encyclopedia

Some routers and packet firewalls rewrite the window scaling factor during a transmission. This causes sending and receiving sides to assume different TCP window sizes. The result is non-stable traffic that may be very slow. The problem is visible on some sending and receiving sites behind the path of defective routers.

Windows 7 is setup out of the box to take full advantage of Window Scaling. To the dismay of "bad" routers.

 

[chev65]

This "bad routers" thing occurs here on a daily basis LOL. I'm not sure that bad is the correct term. I think maybe just outdated routers with no current support might be better. The sad thing is that many of these outdated routers could be made to work if not for the lack of support.

 

[sluk]

You guys are right, I've test the transfer in the LAN and found although TCP Windows Full and Zero also occurs but there is no interruption to the ftp / http downloads. I found that there is not a single TCP Windows Full or Zero occur while using Windows "Copy & Paste". Before I can buy a new router, now I fixed the Internet downloads problem temporary by disabled the Windows 7 TCP Window Auto Tunning:

netsh int tcp show global
Querying active state...

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State : enabled
Chimney Offload State : automatic
NetDMA State : enabled
Direct Cache Acess (DCA) : disabled
Receive Window Auto-Tuning Level : disabled
Add-On Congestion Control Provider : none
ECN Capability : disabled
RFC 1323 Timestamps : disabled

After that I have encounter no more trouble in file download from the Internet, I see no more TCP Window Full issue from the server side but I do have TCP Window Zero as issued by the local adapter but that does't stall the download.

 

[chev65]

Thanks for reporting back in sluk. It's nice to know that those network features can be adjusted to to fix router problems.

With some of the old Nvidia drivers it helped to disable the "Recieve-Side Scaling State" which fixed problems with some of their older drivers on certain machines.