WHAT IS VOIP

VOIP or Voice Over Internet Protocol is a type of transmission medium that is responsible for the delivery of real-time voice and data communication. Unlike its analog predecessor in which the transport functionality was routed via the public switched telephone network (PSTN), calls are now converted from an analog signal to  

a digital format, which is what the Internet Protocol (IP) uses for transmission and delivery, making VOIP possible. Several other key processes, such as signaling, authentication, security, call control, and voice compression, are established by VOIP prior to and during the call setup phase.

 The most common protocols used by VOIP are:

                                       1> session initiation protocol (SIP)
                                       2> Media Gateway Control Protocol ( MGCP)
                                       3> H.323
                                       4>Transport Layer Security (TLS)
                                       5>Datagram TLS (DTLS)
                                       6>Secure Real-time Transport Protocol (SRTP)
                                       7>Zimmermann Real-time Transport Protocol ( ZRTP)