Knowledgebase

In some cases SIP calls are disconnected after 32 seconds.

This happens when the SmartNode involved is B side of the connection.
Looking at a debug log of such a call, it can be seen that several 200 OK and ACK messages are sent back and forth.
This is becuase the other device the SmartNode is communicating with, does not follow the SIP standard as per RFC3261.
See the following explanation;

The reason why the ACK for the 200 Ok from the SmartNode is not accepted, is due to an invalid branch ID in the via header.
Based on the description in RFC 3261, the branch ID for a 2xx response has to be different than in the former messages.
You will find this in section 8.1.1.7, in the RFC 3261.