Symptom

urrently the CUBE is doing DTMF interworking from sip-kpml to rtp-nte. This is the call flow: ITSP -> CUBE -> CUCM The first ReINVITE from CUCM comes with kpml as CUCM CUBE leg is confirmed for that. The REINVITE that CUBE sends out has "a=rtpmap:255 telephone-event/8000". The ITSP complained to the customer saying that it is triggering alerts in their system and CUBE should not be sending payload 255. This below SDP which is sent by CUBE to the ITSP violates the specifications of dynamic payload usage m=audio 19434 RTP/AVP 0 255 100 c=IN IP4 32.253.106.113 a=rtpmap:0 PCMU/8000 a=rtpmap:255 telephone-event/8000 a=fmtp:255 0-16 a=rtpmap:100 X-NSE/8000 a=fmtp:100 192-194 Payload 255 is a reserved payload and should not be used by anyone. Check here: https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml

Conditions

1. Below commands are enabled on the rtp-nte leg dial-peer: rtp payload-type nse 127 rtp payload-type nte 100 2. "asymmetric payload dtmf" is configured under "voice service voip"

Workaround

Remove "asymmetric payload dtmf"

Further Problem Description