rved. Any use is subject to the Terms of Use as given at the website. SWITCH FABRICS SWITCH FABRICS GENERIC TYPES OF SWITCHING PLATFORMS Three generic types of switching/routing platforms are available in the market today: Multilayer Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) switches are network devices that can support TDM-based voice traffic in addition to IP and ATM traffic. IP and ATM switching are handled at a logical layer below the TDM switching unit (crossconnect). Incoming traffic is dispatched to the fabric according to the type of switching needed. For example, IP packets are switched and then the traffic is statistically multiplexed with the ordinary TDM load before it is forwarded to the crossconnect unit. The big problem with the SONET/SDH switch is that it must be designed for a certain mix of traffic. If the actual load mix varies from the designer's target values, the switching efficiency suffers dramatically. This is because the TDM channels must be able to provide fixed bandwidth to the customer. Unless the load is available, this bandwidth is not utilized well, even if many of the TDM slots are assigned statistically to IP or ATM traffic. The hybrid multiservice switch is a networking device that implements parallel processing paths for different types of traffic. This implies that the entire structure expected in network switching/rout- ing devices, such as switch fabrics, line cards, and SO on, must be replicated and their design must be adapted to the types of traffic the switch is built to support. It is obvious that the number of these cards directly affects the load factor of each type of traffic that the switch can support. Therefore, although the problem manifests itself with the same symptoms as with the SONET/SDH switches (namely, the lack of switching efficiency under various load conditions), the cause is essentially the same-the traffic mix can be varied and often unpredictable. Recently, some startup companies have emerged that are developing several t