When the call duration reaches 5 minutes, the call is disconnected automatically.
1. Run the show sip parameter command on the SoftCo to check whether the UseSessionTimer parameter is set to yes.
If yes, the SoftCo sends an Update message to the IP phone at the middle of the heartbeat interval. If the IP phone does not send any responses, the SoftCo sends Update messages to the IP phone every four seconds. After 10 Update messages are sent, the SoftCo regards that the IP phone stops, and releases the call.
2. Check with IP phone, it doesn’t support Update message.
3. Run the config modify sip parameter usesessiontimer no command to disable the SoftCo heartbeat function.
4. Then test and the problem solved.
The possible cause is that the SoftCo enables the heartbeat but the IP phone does not support Update messages.
Actually, also need check the network, the problem will happened when SoftCo send out Update, but IP phone not received.