NMSPrime only supports SIP, not MGCP:
- SIP is widely supported by vendors, while MGCP is not (e.g. AVM Fritz!Box). We need to implement SIP, while MGCP is optional.
- Vendor's development seems to be more in favour of SIP. So new features like video calls should be implemented here as well.
- SIP uses ASCII text based signalling, which make troubleshooting easier.
See https://community.cisco.com/t5/ip-telephony-and-phones/sip-vs-mgcp/td-p/2941310 and https://www.certificationkits.com/cisco-certification/ccna-voice-certification-topics-a-labs/ccna-voice-describe-voip-technologies/ccna-voice-h323-mgcp-sip-and-sccp-protocols/ for discussions and details.