Hello Everyone,

I’ve been grappling with this issue for some months, time to raise the white flag.

Essentially I need to work out a way to configure Kamailio/RTPengine to normalise telephone-events to 101 earlier in the piece.

1. Call comes in from Carrier with INVITE w/SDP, telephone-event payload of 96.
2. INVITE sent to Asterisk with the same SDP, payload = 96
3. INVITE sent from Asterisk to Client with payload = 101
1. 200 OK w/SDP from Client has payload = 101
2. 200 OK w/SDP to Kamailio has payload = 96
3. 200 OK w/SDP to Carrier has payload = 96
4. Asterisk (with Direct Media enabled) sends INVITE to Kamailio with payload = 96, and new media IP of Client
5. Kamailio passes this onto Carrier with media IP of RTPengine
6. 200 OK w/SDP from Carrier has payload = 96 sent to Kamailio
7. Kamailio passes this 200 OK to Asterisk, which responds with ACK and doesn’t do anything further

+---------+              +----------+              +---------+              +---------+

| Carrier | <----1-----> | Kamailio | <-----2----> | Asterisk| <----3------>| Client  |

|         |              |          |              |         |              |         |

+---------+              +----------+              +---------+              +---------+

     ^                       |                          |                        |

     |                       |                         |3|                       |

     |                       |                          |                        |

     +------5---------> +-----------+ <-----------------+------------4-----------+

                        | RTPengine |

                        +-----------+

Big issue is, the Client is expecting telephone-events with a payload of 101, whereas RTPengine is passing it 96 from the Carrier.

• Inbound DTMF only works at client-side if Asterisk stays in path (far from ideal).
• The issue is exacerbated when calls are sent back out to the same or another carrier (forward scenario).
• There’s nothing I can seem to do in Asterisk to change how it handles DTMF in a direct media/re-invite setting.

Any ideas?

Cheers,

Tim Bowyer