Tunnel over UDP or TCP

Solution 1:

Give openvpn a shot. You can create tunnels over UDP or TCP.

Solution 2:

I'm not sure what's causing your particular problem, but you should note that in general it's better for tunnels to use an unreliable transport stream (i.e. UDP) than a reliable one.

The reason for this is that if you do happen to get packet loss the tunnelled TCP layer should be the one managing the retransmission, and not the real transport layer.

If both layers have got retransmission built into them they can start to get in a retransmission war which ultimately kills throughput.

Also, don't forget that any tunneling protocol will reduce the effective MTU (and consequently the TCP MSS). If the MTU and MSS aren't adjusted appropriately you'll see excessive fragmentation and/or dropped packets.