The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

4.6. Four Generations of Switch Integration

As switches have moved from (what we would now consider) primitive bridges to more modem implementations, there have been continual changes and improvements in the level of integration. Higher levels of integration provide lower cost, higher reliability, smaller size, and lower power. In many cases, it is simply not possible to achieve the desired performance level without high integration; the merging of logical functions into a single IC permits the switch forwarding function and the data flow itself to operate much faster.

Switch designs have progressed through four stages of development:^[]

^[] The levels of integration discussed here are applicable both to switches and routers (Layer 3 switches). Routers require a higher level of functionality; hence, the level of integration being achieved typically lags that of switches by at least one generation. Other than this developmental skew, the integration of routing functions into silicon is proceeding in a manner parallel to that of the Layer 2 switches described here.

• Zero integration (1984-1988): Some early bridges were built using general-purpose computers with standard network interfaces (NICs). A small computer with two (rarely more) NICs could be programmed through software to behave as a bridge. Frames were received by the NICs, stored in main memory, processed by the bridge software, and queued for transmission (if necessary) on the appropriate output port.^[]

  ^[] In some cases, such ...