Description
In India, there are several telecom service providers that offer SIP trunking services to businesses and organizations. This article describes call establishment issues with Grandstream IP PBX UCM and SIP Trunks in India and suggested settings to resolve them.
Case 1: Call drop due to 422 Session Interval too Small (BSNL)
Figure 1: UCM’s INVITE shows that its Session-Expires: 90 which is too short.
By default, UCM’s Session-Expires and Min-SE are set to 1800s and 90s under SIP Settings > Session Timer. If these values are modified to a shorter session interval (for eg. the 90s), the remote party will send 422 Session Interval too Small to UCM. This may cause a call disconnection issue upon answering.
To resolve it, kindly ensure that Session-Expires is set to a larger value or disable the Timer.
Case 2: No audio after a call is connected for 5 minutes (TATA)
PBX > SIP Settings > Session Timer > Enable Force Timer
PBX > SIP Settings > Session Timer > Session Expiration > 300