Switches

 Switches

Switches, like bridges also work at layer 2 and provide centralised connectivity like hub. Switches examine the layer 2 header of all the incoming packets and then forwards it to that particular port. This reduces the overhead and improves the overall performance in a network. A switch can be considered as multiport bridge.

Switch is a fast bridge that allows faster processing of frames. Some of the significant functionalities of the switch are: ports are provided with buffer, switches maintain directory for addresses and port numbers, each frame is forwarded after examining the address and forwarded to the proper port number.

There are three frame forwarding approaches: cut-through, collision-free and fully-buffered. Let us discuss each of these briefly in the following section.

Cut-through: A switch forwards a frame immediately after receiving the destination address. As a result, the switch forwards the frame without any collision and error detection.

Collision-free: In collision-free approach, the switch forwards the frame after receiving 64 bytes, which allows collision detection. However, error detection is not possible at this moment, as the entire frame is not yet received.

Fully-buffered: In this case, the switch forwards the frame only after receiving the entire frame. Therefore, collision and error-free frames are forwarded by the switch.

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