One of the principal driving forces behind the evolution to all-IP networks is convergence. Traditionally defined as a technology phenomenon, convergence has more recently been recognized as a troika comprising a technology component, a company component, and a services component. Technology convergence defines the vortex that is inexorably pulling the industry toward packet-based IP networks because it makes sense to do so. As quality of service (QoS) protocols and techniques continue to evolve, and as network devices evolve to be able to respond to QoS demands, services will move to the IP network because it provides a quality-centric, universal protocol substrate that will support all service types across a single network infrastructure. From the point of view of a service provider, this is an ideal construct because it means that they can eliminate the multiple networks, support services, and billing infrastructures that they currently operate in favor of a single converged transport environment. Today, the typical large service provider operates the public-switched telephone network (PSTN), the frame relay network, the ATM network, the IP network, the ISDN and DSL overlay networks, and in some cases, wireless and X.25 networks. For each of these, they must have maintenance, installation, operations, accounting, configuration, and provisioning systems, and personnel and network management centers capable of monitoring them. The fact that they communicate with each other and occasionally share resources and customers makes their management that much more complex.

Now, consider the advantage of the IP...