"The best business telephones in the world."

Hello!

We experience serious connection and realiability issues with two snom phones on different offices. Both phones are configured to use german telekom (DTAG) VoIP services.

The problem is either that the phone shows "unregistered" or when registered that a caller gets the message "unavailable".

When a call is successfully established it gets disconnected after a random amount of time.

The firewall does not show any dropped SIP or RTP data packets.

Question: What can be done to further diagnose and hopefully solve the problem? Is the interruption caused by a keepalive, provider initiated disconnect or some packet loss?

Attached a file with both SIP and system log. My last test with the interruptions was with phone number 01813304114888

Firmware of snom 320 and 715 is both 8.7.5.44

I actually don't know if this is a problem with the phone, provider or network infrastructure.

Thank you!

Best regards,

Bernhard

Attached the log file.