For most of the year we have been dealing with slow, unreliable connection to our network. We have Windows Server 2003 for our file server and domain, and mostly Win XP clients, with a few Windows 7. We have one mobile lab running Windows 7, and a couple of other computers running it as well.
We eliminated several problems this year including blocking DHCP access to non district computers using MAC callout filtering. Sorry, I can’t remember, offhand, where we found it, but the download and instructions are readily available. We replaced our “older than the hills” switches, as well as our access points. The APs were not old, but not as beefy as the replacements, and not all configured the same. All in all, very good improvements for the year. We will be replacing our file server in the near future.
But with all the upgrades and changes, one thing has remained constant: poor connectivity to the network. Students have been able to log on to the network, but then can’t access the file server, or their files don’t open, or worst of all, they can’t save their work. The connections just seem to time out, or go to limbo. Mind you, this doesn’t always happen, and almost never when trying to replicate the issue on one machine. It became clearer that the issues seemed to be mostly affecting the mobile lab running Windows 7.
Research has pointed to Windows 7 TCP auto tuning as a possible suspect. These articles all discuss auto tuning:
Microsoft Technet Forums
SpeedGuide (several tweaks for connectivity)
Microsoft Knowledgebase (slow file transfers)
I opened the command window and executed the following commands on the Windows 7 mobile lab computers:
netsh int tcp set heuristics disable
netsh int tcp set global autotuninglevel=disable
The first command turns off the Windows 7 automatic override for TCP settings, and the second turns off the autotuning. The post by canspec on Seven Forums speaks most directly to this issue. The other links above include other possible reasons for connection problems.
However, this did not seem to be related to our issues. Perhaps more significant were making sure that the Windows did not shut off the wireless when not in use (under power management in properties for the wireless controller) , and that automatic caching of files is turned off.