Switches

Network Switch

 A Network switch is a device that filters, forwards, or floods frames based on the destination address of each frame . 

Switches perform their routing functions at the layers 2 model of the OSI. Some switches  process data at the Network Layer (layer 3), This types of switches are referred to as layer 3 switches or multilayer switches. Switches form an integral parts in networking LAN or WANs . Small office, Home office ( SOHO) applications normally, use a single or an all purpose switches .

The network switch is a very adaptable Layer 2 device; it replaces the hub as the central point of connection for multiple hosts.

 In a more complex role, a switch may be connected to one or more other switches to create, manage, and maintain redundant links and VLAN connectivity. A switch processes all types of traffic in the same way, regardless of how it is used.

Switches moves traffic base on MAC addresses. Each switch maintains a MAC address table in high-speed memory, called content addressable memory (CAM). The switch recreates this table every time it is activated, using both the source MAC addresses of incoming frames and the port number through which the frame entered the switch.

As mentioned earlier, switches operates at the data-link layer of the OSI model, switch function is to create a different collision domain per switch port. Let take an example of Four computers PC 1, PC 2, PC 3, PC 4 attached to switch ports, then PC 1 and PC 2 can transfer data between them so as PC 3 and PC 4, simultaneously without interfering with each other's conversations. 

Unlike the hub, which allows the sharing of bandwidth by all port, run in half-duplex and is prone to collisions of frames and retransmissions. 

With some ISPs and other networking environments where there is a need for much analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some switches  provide in built firewall,  network intrusion detection and performance analysis modules that can plug into switch ports.