Switching

Layer 2 switching provides the following:

• Hardware-based bridging (ASIC)


• Wire speed


• Low latency


• Low cost

Switch functions at layer 2:

• Address learning


• Forward/filter decision


• Loop avoidance

Internal processing variations:

• Store and forward - the switch must recieve the entire frame before forwarding the first bit of the frame.


• Cut through - switch starts sending frame as soon as possible. It may cause errors, because frame check sequence(FCS) is in the Ethernet trailer.


• Fragment free (Adaptive cut-through) - works the same as cut through, but it waits to recieve the first 64 bytes of frame. 64 because collision in CSMA/CD should be detected during first 64 bytes.