Different network devices used in network.

Hello friends in this section we will discuss some important network devices used in a computer network with different type of LAN, MAN, WAN etc. Let us discuss each and every network device 

Repeater – A repeater operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do no amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength. It is a 2 port device.

Hub – A hub is basically a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices. Hub is a generic term, but commonly refers to a multiport repeater. It can be used to create multiple levels of hierarchy of stations. 

Bridge – A bridge operates at data link layer. A bridge is a repeater, with add on functionality of filtering content by reading the MAC addresses of source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device. The device that can be used to interconnect two separate LANs is known as a bridge. It is commonly used to connect two similar LANs. 

The bridge operates in layer 2, that is datalink layer. Advantages, are higher reliability, performance, security, convenience and larger geographic coverage. Key features of a bridge are mentioned below: 

•  A bridge operates both in physical and data-link layer 
• A bridge uses a table for filtering/routing

Switch – A switch is a multi-port bridge with a buffer and a design that can boost its efficiency(large number of ports imply less traffic) and performance. Switch is data link layer device. Switch can perform error checking before forwarding data that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. A switch is essentially a fast bridge having additional sophistication that allows faster processing of frames. Some of important functionalities are:

• Ports are provided with buffer 
• Switch maintains a directory: #address - port# 
• Each frame is forwarded after examining the #address and forwarded to the proper port#

Comparison between a switch and a hub 

Although a hub and a switch apparently look similar, they have significant differences., both can be used to realize physical star topology, the hubs works like a logical bus, because the same signal is repeated on all the ports. On the other hand, a switch functions like a logical star with the possibility of the communication of separate signals between any pair of port lines. As a consequence, all the ports of a hub belong to the same collision domain, and in case of a switch each port operates on separate collision domain. Moreover, in case of a hub, the bandwidth is shared by all the stations connected to all the ports. On the other hand, in case of a switch, each port has dedicated bandwidth. Therefore, switches can be used to increase the bandwidth of a hub-based network by replacing the hubs by switches

Routers – A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.