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Microsoft® Lync Server 2010 Unleashed by Tom Pacyk, Andrew Abbate, Alex Lewis

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Brief History of UC

Before Voice over IP (VoIP), voice calls were sent over a dedicated network. Each call passed through a dedicated circuit and was switched from one point to the other, hence the term circuit-switched. Although this guaranteed a quality connection, it required dedicated processing power and physical connectivity. For example, the wire that went from your home telephone to the central office (CO) connected you to a physical port on the CO telephone switch. The processor of the CO switch had to constantly monitor each port to determine whether a particular phone (port) made a request to dial a number or access a feature, such as call forwarding.

With a telephone connected to a dedicated network, either the public switched telephone ...

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