Innovaphone swphone with VPN connection

 What

Innovaphone swphone with PPTP connection on Windows pc

 Problem

The swphone drops the call after 3 minutes talking!

 Solution

My client got calls being dropped when using the Innovaphone swphone on his Windows pc, I first checked the usual stuf. Is he running the correct firmware? Is the license ok? Can I succesfully ping the PBX for longer then 3 minutes. Because mostley this is an network error.

But everything was fine, the call got dropped and the PBX was still reachable.

I suspect the issue could be related to the NAT Mapping at our NAT Router getting discarded too soon. We notice that different ports are used for the RAS messages while the Registration Keep Alive mechanism is happening.

Proposed Time to Live
This is the number of seconds after which the registration request to the Gatekeeper has to be refreshed (a.k.a. lightweight registration). You can set this to a value between 10 and 1800 seconds, the default is 1000. Please note that that this value is proposed to the gatekeeper which will respond with a modified (most likely lower) number. An innovaphone gatekeeper will respond with a value of 120 for example.

This means every 120 seconds there is a Registration Keep Alive mechanism with RAS messages. The RAS message is comming with a different Source Port, this most likely means the NAT Mapping was discarded under the 120 seconds on the NAT router.

Result it's that the RAS Keep Alive mechanism will not work anymore and the registration will be refresh fully what cause ongoing calls be dropped.

We can try to reduce the RAS keep alive timer from 120 seconds to 60. To do so in the PC were softwarephone it's running do:

http://x.x.x.x/!config change H323 /ras-rrq-ttl 60
http://x.x.x.x/!config write
http://x.x.x.x/!config activate
http://x.x.x.x/!reset

After the softphone restart we did test the settings and everytime this works!