fm-package is required for RFC2833 usage with MGCP and/or MGCP-SIP interworking. There are two variants of this i.e. NTE-CA and NTE-GW. In GW-controlled mode, GWs negotiate DTMF transmission and RTP PT values by exchanging capability information in SDP messages. That transmission is transparent to the CA. For this, both ends/GWs should be running MGCP and connected to same CUCM.
In CA-controlled mode, CA/UCM will negotiate DTMF relay capabilities on behalf of the gateways (SDP messages are sent to CA). This is a must when the other GW/Endpoint is non-MGCP. After negotiation, CA will instruct MGCP gateway to use the agreed RTP-NTE values.
I'm confused. I have two MGCP gateways in NTE-CA mode for DTMF relay. One has the fm-package enabled, and the other doesn't. Strangely, on the gateway that does NOT have fm-package enabled, DTMF works fine.
Do you have a MGCP-SIP inter-working ? On the gateway where you do not have this enabled, does DTMF work using RFC2833 ? Is there a noticeable difference b/w the call flows for both the setups ?
