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When connecting the MOH we could see DTMF mismatch on the CUBE which made the CUBE to allocate Transcoder (LTI). Generally, the MOH do not have any DTMF method (which is expected) and the Agent leg supports RFC2833, this has resulted in XCODER allocation.
Ack comes from CUCM when the call is placed on hold comes with no DTMF capabilities which creates a DTMF mismatch. ITSP negotiated RFC2833 and now inside leg changed from RFC2833 to RAW media.
1.Invoke MTP on CUCM SIP trunk 2. LUA script on CUCM to add below parameters: a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 (m=audio.*)" "\1 101" ***LUA SCRIPT**** M = {} trace.enable() function M.outbound_ACK(msg) trace.format("---- Ready to get SDP") local sdp = msg:getSdp() if sdp then trace.format("---- sdp found") local moh_line = sdp:getLine("a=", "X-cisco-media:umoh") if moh_line then trace.format("---- MoH line found") local audio_line = sdp:getLine("m=", "audio") if audio_line then trace.format("---- audio line found , length is %d", string.len(audio_line) ) local audio_modified = (string.sub(audio_line, 1, (string.len(audio_line)-2))) .. " 101\r\n" -- extracts string from 1st character to Length-2 characters. Last two characters are \r\n which we ignoring while extracting the string. trace.format("---- new audio line %s", audio_modified) sdp = sdp:modifyLine("m=", "audio", audio_modified) sdp = sdp:addLine("a=rtpmap:101 telephone-event/8000\r\n") sdp = sdp:addLine("a=fmtp:101 0-15") msg:setSdp(sdp) end end end end return M
This behavior is from 16.12.5 onwards this has to reworked as with moh we shouldn’t invoke dsp PSIRT Evaluation: The Cisco PSIRT has evaluated this issue and determined it does not meet the criteria for PSIRT ownership or involvement. This issue will be addressed via normal resolution channels. If you believe that there is new information that would cause a change in the severity of this issue, please contact psirt@cisco.com for another evaluation. Additional information on Cisco's security vulnerability policy can be found at the following URL: http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html