PDF of this tutorialEarly multiservice devices emerged in the market as an afterthought when vendors added a hodgepodge of ATM, switched multimegabit data service (SMDS), and IP cards into frame-relay switches.
Following that, the first generation of multiservice switches used a switching fabric based on ATM technology, which was specifically designed for supporting multiple services (see Figure 3). These products offered better integration of multiple advanced data services into a common chassis and avoided the necessity of purchasing and managing several different switches to support many different protocols. However, these switches still required protocol-specific hardware within each chassis to cope with the varying needs of customers and suffered from the high cost of implementing several protocol engines. The result was poor protocol and service agility.
Figure 3. First-Generation Multiservice Switches
The second generation of multiservice switches introduced the breakthrough concept of any service on any port at any time. ASAP@ multiprotocol uses a software-defined network infrastructure, as shown in Figure 4. An ASAP@ multiprotocol engine allows the configuration of any advanced data service on any customer port, without requiring a varied inventory of protocol-specific hardware modules. No juggling of cables and connectors to configure services is necessary; all services are provisioned on a software-defined basis by the touch of a keyboard in a network operations center.
Figure 4. Second-Generation Multiservice Switches
The third generation of multiservice switches revolutionizes the entire network architecture through integration and multilayer switching, as shown in Figure 5. Integrated circuit and packet switching occurs on the access side, while ATM–based packet switching takes place in the backbone. In between the two switching fabrics resides the full array of protocol engines, enabling an enormous number of various access interfaces to be accommodated.
Figure 5. Third-Generation Multilayered Switching.
Multilayered, converged networks are the answer to the service providers' problems of disparate network operations, expensive equipment infrastructure, and inefficient utilization of expensive facilities. They provide a way for service providers to respond quickly to the exploding service demand with a rapidly evolving service and feature mix.
