[Openswan Users] RDP connection slow

Andreas Lüdtke andi.luedtke at gmx.de
Tue Jan 31 14:31:48 CET 2006

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

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?



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