VPN good with FTP, very bad with NT file server

[CHM1]

Could anybody confirm this :
I use VPN with Com21 Pro Cable modem; speed is 256kbps.
When I transfer files using FTP Throughput is good (ca 30 ko/s).
But when I browse a directory under Windows Explorer or when I copy/paste a file, or save a document with MS Word it's tremendously bad (up to one minute for 20 ko).
I tried to trace packets and here's what I saw.
Transmission delay is a 100 / 1 ratio compared with a 10 Mbps Lan connection.
With FTP, packets are acknowledged within the TCP Window (one ACK for some packets) and even if the ack comes back with a 100 ms delay you have transmitted more than one packet within the TCP window, so you have a good throughput.
With NT access, you use the SMB protocol (alias CIFS) and you see plenty of commands to browse a directory or to read a file, and each packet containning a command must be acknowledged (with a 100 ms ca delay on my VPN); so when cumulated you get a huge response time...
Is this true or false... Would you please give me your opinion and more ... the proof accessing a NT file server trough a relatively slow VPN is not a good idea; but then where is the solution ?
Thanks .

 

[Guest_imported]

You probably need to change the MTU settings on the client pc. VPN adds a little overhead to your packet sizes, so dropping the mtu settings will help. There are many documents describing which registry key to change.

Good Luck

 

[CHM1]

I think the MTU settings is no concern, because frames are not fragmented.
It's only the response to a frame which is long no matter the MTU settings.