VoIP networks are very popular these days. In order to support communication between traditional PBXs, Cisco IP phones, analog PSTN, and the analog telephones, all over IP network, quite a number of protocols are needed. Few protocols are indicating protocols (for instance, MGCP, H.323, SIP, H.248, and SCCP) used to position, sustain, and bring down a call. Other protocols are marked at the real voice packets (for example, SRTP, RTCP, and RTP) relatively indicating information. Few of the most common VoIP protocols are shown and described here.