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Remote Networking through VPN

By steve.rocco ·
Running Raptor mobile 6.5 for firewall. Users connected through high speed @ home and tunneling into the network. They are trying to copy files 10mb or more and losing connection. Our Bandwidth is fine. Anyone have any ideas?

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by Oldefar In reply to Remote Networking through ...

Seems to me that your problem might be with fragmentation, and in particular with you end device being unable to keep up with rebuilding the arriving packets.

Most comm is configured for an MTU (maximum transmission unit) equal to a full ethernet packet. This is great until you start layering protocols on top. I first encountered this with frame relay. OSPF was transmitting correctly based on MTU and maximizing the packets. Frame relay was adding the DLCI headers, and forcing each packet to fragment. Receiving routers could not keep up with the rebuilds during convergence (full exchange) and would give me OSPF errors.

Using VPN you are putting IP packets into IP packets. Since you are doing a file transfer, the end device IP stack is trying to optimize with a full packet. When you add the VPN wrapper, your packets fragment and trouble begins. Eventually, the receiving side is unable to keep up (hence the problem with large files).

Try reducing the MTU in the sending unit IP stack prior to the VPN aspect. If you let me know what the users have for OS, I might be able to point you to where this is set. Otherwise, you can do a knowledge base search at Microsoft for their OS and a Google search for any other OS you may be running.

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