Although the acronym for both VoIP and SIP appeared to be similarly confusing, their definitions make it easier to understand their differences. Voice over Internet Protocol (VoIP) and Session Initiation Protocol (SIP) are technically as different as night and day. In fact SIP is a signaling protocol that uses Voice over IP as a trunk, or base.
VoIP (Voice over Internet Protocol)
Voice over Internet protocol (VoIP) is the technology that is used to send voices across packet networks. For years, individuals used Mobile Networks and PSTN Networks as a way to communicate. In the evolution of the network technologies and the Internet, innovative quality carrier-grade Voice over Data Networks were developed. In essence, the technology made it possible to send and receive phone calls over an internal network or the Internet.
SIP (Session Initiation Protocol)
Session Initiation Protocol (SIP) is a highly developed application layer protocol that was designed to establish, modify and terminate multi-media sessions that include VoIP call technology. The SIP technology was also developed to handle multiple sessions into existing sessions including multi-cast conferences. Other than just sending voices over packet networks, a Session Initiation Protocol uses the VoIP signaling protocol environment as a way to manage call establishment, call control and termination. After every call has been terminated, it generates a Call Data Record (CDR)
Differentiating VoIP and SIP
VoIP uses innovative technology of modern telecommunication networks. SIP is a control protocol (signaling) that finds its function inside VoIP. In general terms, VoIP technology uses media and signaling, while SIP refers only to signaling.