Using tinc on a blocked network..

[willy at gardiol.org]

hi guys!
i was using +PPP over SSH tunneling in the past to achieve a
kind of VPN between two networks:
A is a public network 
B is a private network

The problem is that network B is behind a firewall that for
some reasons cannot be opened whatsoever. This mean that:
Network B can freely connect to network A (SSH, for example)
Netowkr A cannot access network B in any way (except, trough
a connection already open by Network B).

Up to now i have used a PPP connection over a SSH tunnel  in
this way:
Network B set up a SSH connection to Netowrk A 
PPPD and PPP are used to setup a virtual network interface
between the two

The objective is: being able to do SSH from Network A to
Network B.

Now, the PPP+SSHs etup is clumsy and very prone to errors, i
would like to use tinc.

I have tried, but seems like i cannot make it work! 

This is part of the log from Network A:
Sending PING to client (81.208.74.190 port 22971): 8
Sending 2 bytes of metadata to client (81.208.74.190 port
22971)
Flushing 2 bytes to client (81.208.74.190 port 22971)
Got PONG from client (81.208.74.190 port 22971): 9
Read packet of 98 bytes from Linux tun/tap device (tun mode)
Sending packet of 98 bytes to client (81.208.74.190 port
655)

Note that i cannot open any port (or DMZ in any way) the
firewall at 
81.208.74.190!

I have tinc running on both Network A and Network B.

Any suggestion or help is highly appreciated!