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Chapter 2. A Bit of History > Summary - Pg. 29

2.4 Summary incorporate not only voice and video, but also presence, IM, data sharing, and so forth, so that SIP has become the key IP signaling protocol for enabling a true real-time peer-to-peer total communications experience for end users. A completely new paradigm for VoIP, different from H.323 and SIP, was born in 1999, when some new and incumbent carriers declared their urgent need to converge their voice and data infrastructure. The industry response was the IETF MGCP (Media Gateway Control Protocol), later to become the IETF and ITU MEGACO (Media Gateway Control). MEGACO gave birth to the concept of the call server, which has now been implemented in the networks of quite a few operators. Whereas H.323 is already considered legacy, and SIP clearly represents the future-proof approach that is already a reality today, the MEGACO concepts have found their way into some interim architectures--for example, the 3GPP R4 core network split architecture conceived as an evolution of the circuit-switched domain for GSM/UMTS operators. Already in 2007, there are millions of Internet users subscribed to SIP-based VoIP or messaging services. Very popular communicator applications such as Microsoft's or Yahoo!'s are based on the Session Initiation Protocol, and software providers are clearly betting on SIP. Also, most companies are looking into this 29