Expert knowledge of VOIP protocols such as SIP, Megaco/H.248, MGCP, DNS, LNP, TCAP, SDP, RTP, DIAMETER), IMS (Audio/Video call signaling, Instant Message, RCS, Presence, Subscription), VoNR, VoLTE / LTE EPC. Expert knowledge of the call flows of services and features such as Voice, Messaging, UCE, UT, USSI, HTTP, VoLTE, VoWiFi, IR92, IR94, AS262 HO, WPS, RTT, N11, International Wi Fi and S8HR.