Strange slow file download via UNC or mapped drive

[pete]

Mods: I'm not sure whether this is a networking or windows problem atm.

I have a strange problem with slow file downloads (but not uploads) from a file shares on a particular Windows 2003 R2 server (fully patched) while using XP SP2 clients.

Server --- Backbone Switch --- Dumb switch --- client
						|
						|-- Managed switch--client

If I download any file over a couple of mb from the server using an affected XP Pro SP2 (fully patched) client, file transfer is very slow. A 32mb file takes about 10 minutes.

Whether I use an unc share or a mapped drive, the speed is the same. If I download a file via http the speed is better, but still slower than it should be.

If I use the same machine to upload a similar sized (or identical file) to the server, it copies instantly.

If I move the client to a network location where there isn't a "dumb" (unmanaged) switch in the path to the server, downloads are fine.

However, uploads and downloads to shares on the server in question are fine through "dumb" switches on Linux boxes and downloads are fine from any other 2003 R2 server using the same clients + dumb switch.

Server patch level is identical and the misbehaving server runs IIS, WDS and WSUS.

FQDN, netbios names and ip addresses resolve correctly on all clients (affected and unaffected) and the server. There is no filtering that would prevent the XP clients accessing the server - no firewalls are enabled on the server or the affected clients.

Antivirus is Mcafee 8 on all windows clients and servers - turning off scanning on file writes doesn't improve speed.

Network traffic is mostly non-existant due to internal exams for the whole school.

I've reloaded the nic drivers on the affected server and clients.

While the dumb switches do need replacing (allowing for budget) I'm baffled as to why only this server through a dumb switch is affected and only for downloads on XP clients.

Any ideas?

[Geoff]

Check for driver updates for the NIC card used in the server. It might be a RSS issue brought on by SP2.

[PiqueABoo]

Don't know, but I have seen an XP box with a specific NIC get as far as, but then fail to download policy (approx 100K file sizes) through a particular brand of switch. Solution was to update the XP NIC driver.

[pete]

I'm still working through this, and noticed craiglay is having similar problems with a broadcom netextreme card, though mine is a BCM5708C NetCtreme II.

http://edugeek.net/index.php?name=Fo...ewtopic&t=9341

I've tried the latest drivers from Dell and Broadcom without any joy.

RSS is disabled in the registry and in the option on the Broadcom nic, I'm currently trying exploring the Broadcom driver config options to see what they're supposed to do.

[pete]

Right, got this fixed and working at proper speeds on all clients, regardless of the switches they're using.

After a bit more googling, I solved my problem by adding another registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DisableTaskOffload = 1

This is in addition to explicitly disabling Recieve Side Scaling on the network adaptor and setting the the EnableRSS=0 key in the registry.

[PiqueABoo]

Interesting.. I've got a recipe which has you turning off "Offload Transmit TCP Checksum" for Intel GB NICs... have never checked, but it maybe it breaks things in a similar way.

[craiglay]

Hmmm, the EnableRSS=0 key was already in my registry... Didn't need to add.

It is a vanilla Server 2003 R2 With SP2 installed straight away. I will try the DisableTaskOffLoad trick tomorrow.

Craig

[PiqueABoo]

This is in addition to explicitly disabling Recieve Side Scaling on the network adaptor and setting the the EnableRSS=0 key in the registry.

It pays to be interested because I very recently ran into one of these. Wasn't room for trying all the permutations so did the RSS and offload disables in both NIC properties and the MS TCP/IP reg settings.

Has anyone had the time & energy to pinpoint exactly what is needed e.g. is the DisableTaskOffLoad enough (unless you're doing NAT)?