What is Switch in Networking?

In this tutorial, we are going to see What is Switch in Networking?

A switch is a multi-port bridge, which means that it is an active element acting at level 2 of the OSI model.

The switch analyzes the frames arriving on its input ports and filters the data in order to direct them only to the appropriate ports (this is called switching or switched networks). So the switch combines the filtering properties of a bridge and the connectivity properties of a hub.
 

 
 
The switch uses a filtering and switching mechanism to direct data flow to the most appropriate machines, based on certain elements present in the data packets.

A Layer 4 switch, operating at the transport layer of the OSI model, inspects the source and destination addresses of the messages, builds a table that allows it to know which machine is connected to which port of the switch (in general this process is done by self-learning, meaning automatically, but the switch manager can make additional adjustments).

Knowing the port of the recipient, the switch will only transmit the message on the appropriate port, leaving the other ports free for other transmissions that may occur simultaneously. As a result, each communication can be done at full speed (no more bandwidth sharing), without collisions, with a very significant increase in network bandwidth (at the same speed).

The most advanced switches, called Layer 7 switches (corresponding to the application layer of the OSI model) are capable of redirecting data based on advanced application data contained in the data packets, such as cookies for the HTTP protocol, the type of file exchanged for the FTP protocol, etc. For example, a Layer 7 switch can provide load balancing by directing data flows entering the enterprise to the most appropriate servers, those that have the least load or respond most quickly.
 
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