As I had wrote before I had some trouble with the connection on one of my servers.
I suggested to implement SIP-Spoofing, but I didn’t use it.
What I did, was removing the daily tunnel disconnection out of the crontab. When I investigated the log-files it was as if a buffer run out of memory.
With the previous server (other hardware) it was needed to reset the connection every night.
So at this moment the server is up for almost 63 days