[Openswan Users] RDP connection slow

[Andreas Lüdtke]

Hi group,

I've a working ipsec tunnel between two lan and RDP (Windows Terminal Server protocol)
connections over this tunnel are VERY slow, but only in one direction! Here are the
details:

The company lan is connected to the internet via a commercial VPN router and a 2MBit SDSL
line. My home office is connected to the internet via an Openswan (2.4.4) router an a
1024/128 DSL line.
When I connect from my home office to the company Terminal Server, everything is fine.
When I connect from the company to the terminal server in my home office it is very, very
slow. I know I only have 128kbits upstream bandwidth, but I made it possible to connect
from the internet directly (via port forwarding) to this terminal server. If I connect via
this way (no ipsec tunnel), I have a normal connection without speed problems.

Maybe this could be an mtu problem, so I measured some pings back and forth:

Company to home office: ping with size 7280 works, size of 7290 and more doesn't work 
Home office to company: ping with size 3850 works, size of 3860 and more doesn't work

When I tried to ping the company with a size of 3860, I can't ping the company anymore
even with smaller packet sizes. I can't even ping known websites! It looks like the router
is somehow "blocked". After a minute or so, this blocking vanishes and I can ping the
company and websites.

Does someone has an explanation or even better a solution for this?

Thanks

Andreas