Calls dropping after 32 seconds

Calls dropping after 32 seconds is a common problem in VoIP communications. Below is an explanation of why this problem occurs and how to solve it.

How this problem occurs:

When a SIP call is established between two endpoints, the callee sends the SIP response "200 OK" to confirm that media data (audio) can be transferred between the two endpoints. If the callee does not receive the SIP response "ACK" (acknowledgment), the callee sends "200 OK" several more times before ending the call if no ACK is received. This happens over a span of 32 seconds. During these 32 seconds, audio is delivered between the two endpoints until it cuts off.

How to solve it:

• Switch to TCP: In the Impact Phone clients, there is an option to set "Transport" to either TCP, UDP, or TLS. Set it to TCP to prevent calls from being cut off.
• If UDP is required: Check your firewall settings to ensure UDP is not blocked on the required ports. Also, keep in mind that UDP requires a STUN server.