Tshoot RFC 2833 - CUCM Traces

[gpsriramdc]

Hi ,

How we can troublshoot RFC 2833 DTMF issues using ccm logs. Since it's the Inband method all the DTMF messages are passthrough the RTP.

in my case call flow will be

7961 (SCCP) --CUCM --SIP---ITSP(SBC) .

When i checked the Phone console logs DTMF digits are transfered to CUCM.but the DTMF not working for those calls.

Thanks in advance..

[Marek Janecek]

Hello,

what version of CUCM are you running ?

(Older versions need activated MTP and MTP required option checked in SIP trunk to SBC)

There could be other issues but this the most common.

Marek

[gpsriramdc]

Hi ,

We are using 7.1.5SU4 . Is RFC2833 won't work MTP in the SIP trunk.

Thanks

[Marek Janecek]

SCCP phones are not able to produce RFC 2833, they transmit it via SCCP messages to CUCM, so you need to put there something which will add RFC2833 to ordinary RTP stream -> you add MTP to RTP path, which will do the job

It's described at:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/8_5_1/ccmsys/a08sip.html#wp1127648

So try to enable MTP on CUCM ( if it's not already running) and check that MTP required checkbox at SIP trunk configuration to SBC ( it usually helps )

Marek

[Jonathan Schulenberg]

Almost all phones, SCCP or otherwise, support RFC2833 at this point. Only 7940/7960 other gen one models that have not had firmware updates in years didn't get this capability added. The phone will send SCCP OoB or KPML if it's a SIP endpoint to CUCM in case interop is needed through an MTP; however, it will also send RFC2833 to the trunk if instructed to do so. You'll probably want to confirm that RFC2833 gets negotiated in the SDP of the call on the trunk. Once that is confirmed a few debugs on CUBE (or whatever your SBC is) would tell you whether the phone is actually sending the digits. If it was negotiated with CUCM and CUBE never gets the packets it's likely a phone firmware defect. You could upgrade the firmware and if that doesn't fix it open a TAC case.

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