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The introduction of converged networks (VoIP in particular) has been a gradual evolution and not a revolution. Much like the migration from the COBOL programming language to new object-oriented languages, separate voice and data networks will be around for some time to come. Gradually, though, they will fade away to the point of having only one converged network for voice, data, and video.

As we go through the material for this week's lecture, we will view VoIP from a number of different architectural perspectives. During this discussion, view it with an eye toward the optimal characteristics of each design. Over time, we expect a single approach to incorporate the best features from the many available solutions.

Because routers are an integral part of the IP network, it is logical to leverage that infrastructure as part of the converged solution.

Strengths of the Router-Based Architecture

Two key strengths of routers are that they are routing devices and are IP-based. This is extremely beneficial since voice is migrating to a packet-switched environment and will now be routed throughout the network.

Given the necessity for them to grow, IP networks are designed to be scalable. As such, routers are designed for scalability. This allows a VoIP network to be expanded relatively easily without encountering significant difficulties.

Weaknesses of the Router-Based Architecture

The weaknesses of router-based architectures revolve around the fact that routers are routers and not PBXs. This does not mean that a router cannot support telephony applications, but it does mean is that there is a substantial development cycle associated with this implementation. Given the development cycle needed to incorporate telephony features and capabilities, early generations of router-based solutions will be limited in scalability and feature sets. The feature sets revolve around end-user features, administrative features, call routing features, and so forth.

Note that it...