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Hi All,


Call flow :
SCCP phone (7960 model) --> CUCM -- SIP Trunk (EO, insert MTP if reqd) --> PSTN --> SIP Phone


Q1. Since SCCP phones support OOB DTMF, SIP phones support in-band and for the SIP Trunk DTMF is configured to be RFC 2833, in this case who will invoke the MTP for DTMF mismatch? the SCCP phone? Why?


Also if this would have been the call flow :

SCCP phone (7960 model) --> CUCM --SIP Trunk-- --> H.323 VGW --> PSTN --> SIP Phone

In this case, SCCP - OOB, SIP Trunk - RFC2833, H.323 - OOB, SIP - inband. In this case who will invoke MTP for DTMF mismatch?


Q2. Since we know that the the older SCCP phones - 7960 doesn't send the media information reqd to create Early Offer (EO) thus an MTP has to be invoked by the SCCP phone to provide the media info reqd to create EO. Thus in this case will there be 2 MTPs invoked - one for DTMF mismatch and the other for creating Early Offer?


Q3. In Q2, the media info that is going to be sent to the CUCM for creating EO, the MTP will send it's IP and port for RTP, correct? What will the codec be? Will the codec be the selected from the SCCP phone-MTP region pair? Or the SCCP phone-SIP trunk Region pair?



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