The ______________ is an IETF-defined signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP).

A.
Session Initiation Protocol

B.
Real-time Transport Protocol

C.
SS7

D.
VoIP

Explanation:
The Session Initiation Protocol (SIP) is an IETF-defined signaling
protocol, widely used for controlling multimedia communication sessions such as
voice and video calls over Internet Protocol (IP). The protocol can be used for
creating, modifying and terminating two-party (unicast) or multiparty (multicast)
sessions consisting of one or several media streams.