Files become corrupted during transmission

Jul 20 05 11:22 pm

I am using the trial version of the VPN. I can see the machine and the files. When I modify a file and try saving to the host, I get an error message that the data was lost.

This seems to be a one-way issue as I downloaded a total of about 50MB of files from the host but "most" uploads get lost.

When on the host, any files that were said to be "lost" by the remote are then said to "corrupted" when I try to open them, thus resulting in a loss of data...

I also seem to loose connection frequently and am not allowed to join the host.

I am running Win2k on the host and XP Home on the remote

Any suggestions?

Jul 21 05 8:44 am

Have you checked and adjusted the MTUs? I had a similar problem connecting from home, but managed to resolve it by adjusting the MTU to the most appropriate value. (Using the non-fragmentable ping test to establish MTU, then DrTCP to set the MTU)

Jul 21 05 9:08 am

I reduced the MTU to 500 and it seems to be working. Is there a problem keeping it this or low, or should it be at maximum?

Jul 21 05 9:08 am

I reduced the MTU to 500 and it seems to be working. Is there a problem keeping it this or low, or should it be at maximum?

Jul 21 05 9:11 am

It primarily affects transmission speed so ideally it should be set to as much as the link will allow.

Jul 21 05 9:28 am

How do I perform a "non-fragmentable ping test"? That one is over my head...

Jul 21 05 9:35 am

From the command line run "ping -f -l 1400 <ip>". Replace <ip> with the IP-address of the remote VPN endpoint. That pings it with a packet that is sized to 1400 bytes and has the do not fragment flag set.

If it is too big to pass through the VPN without fragmenting you will get the "Packet needs to be fragmented but DF set." message back. Simply reduce the size by 100 bytes (E.g. -l 1300) and try again until it passes through 100%. That value will be the optimal MTU.

Jul 21 05 10:41 am

Thanks for your help. 470 sounds like an ugly number.

Jul 21 05 10:46 am

Ah, but remember that is with the adjusted MTU, isn't it? (I.e. you've already changed it down to 500, thus when pinging across the VPN - the headers ... etc.)

You can find the settings for MTU here where Microsoft describes the best values for IPv4.

Jul 21 05 1:41 pm

And more importantly, it works now. Something it did not do earlier ;>)

Thanks for your help

T