A network switch is a computer network device with multiple ports in one network, whose task is to copy frames from one computer's port to another. The first Ethernet network switch was pioneered by Kalpana (computer networking equipment manufacturing company in Silicon Valley established by an entrepreneur of Indian origin, Vinod Bharadwaj) in 1990.
Switches operate at Layer 2 of the OSI Model; the Data-Link Layer. This is in contrast to routers, which operate at Layer 3 of the OSI Model, the Network Layer. The phrase network switch does not commonly include unintelligent or inactive network components such as hubs and repeaters.
A switch stores the MAC Address of each and every device which is connected to it. The switch will then evaluate every frame that passes through it. The switch will examine the destination MAC Address in each frame. Based upon the destination MAC Address, the switch will then decide which port to copy the frame to. If the switch does not recognize the MAC Address, it will not know which port to copy the frame to. When that happens, the switch will broadcast the frame to all of its ports.
Switches vs. Hubs
Before switches became available, devices called hubs were common. Hubs were less intelligent network devices that always copied all frames to all ports. By only copying frames to the destination ports, switches utilize network bandwidth much more effectively than hubs did. Switches inspect the packet headers and send them to the proper destination only. 10/100 Ethernet Hubs are only half duplex which means that every computer can only send or receive data frames at a specific time and not concurrently. A switch can function at full duplex permitting the computers to send and receive data frames at the same time i.e. simultaneously.
Switches vs. Bridges
Another piece of network hardware related to the switch is the Bridge. A Bridge is effectively a two-port switch. Because there is not much market for a two-port switch, bridges are no longer manufactured.
