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Stumped - Slow WAN access with SMB traffic

Greetings - I could use an expert on this. We have a Win2003 network/WAN using a 256k VPN tunnel. The performance when trying to copy files and add/print is very poor.

We had the WAN line tested, and had Microsoft look at the server.

Our throughput seems fine using HTTP or FTP transfers. Using SMB (file copy, printing) is very poor or timing out. I'm getting RPC timeouts too. Is there anything in the WAN that can cause this? Wish I had more details - not a network engineer.

Thank You

2 REPLIES
Bronze

Re: Stumped - Slow WAN access with SMB traffic

Hi,

The slow SMB performance may occur if a delayed TCP/IP acknowledgement (also known as a TCP ACK) occurs in a "SMB: C NT transact - Notify Change" packet. Typically, this issue occurs if you use Windows Explorer to copy the files to a domain controller. However, this issue may also occur if you use a command prompt to copy files or if the focus is on the destination folder in Windows Explorer (when the Change notification is involved). This issue occurs as soon as you perform an SMB copy procedure (from any program) to a remote target folder that has been also invoked by a "change notification" request (from any program).

By default, this behavior occurs as soon as SMB is using security signatures. If security signatures are configured, SMB must be processed synchronously by the redirector. The redirector has to wait until the current SMB command is fully processed before it continues with the next one. The redirector waits until it receives the TCP/IP acknowledgement from server.

Workaround:

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system.

Use Registry Editor at your own risk.1. Click Start, click Run, type regedit in the Open box, and then click OK.

2. Locate and then click the following key in the registry:

HKEY_LOCAL_MACHINE\System\Current ControlSet\Services\LanmanServer\Parameters

3. Double-click the RequireSecuritySignature value, type 0 in the Value data box, and then click OK.

4. Double-click the EnableSecuritySignature value, type 0 in the Value data box, and then click OK.

5. Quit Registry Editor.

By default, the EnableSecuritySignature value is set to 1 (ON) on a domain controller and is set to 0 (OFF) on a non-domain controller. As a result, slow SMB copy performance only occurs when you copy items to a domain controller.

HTH

Regards,

Bjornarsb

Bronze

Re: Stumped - Slow WAN access with SMB traffic

Hi,

I also found this article:

http://support.microsoft.com/kb/321098/

BR,

Bjornarsb

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