NETWORKING DEVICES

Computer networking devices are also called network equipment, Intermediate Systems (IS) or interworking Unit (IWU). Common basic networking devices which are very commonly used nowadays are:

1. 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 not 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.

2. Bridge – A bridge operates at data link layer. A bridge is a repeater, with add on the 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.

3. 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.  In other words, collision domain of all hosts connected through Hub remains one.  Also, they do not have intelligence to find out best path for data packets which leads to inefficiencies and wastage.

4. Gateway – A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models. They basically work as the messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router.

5. Switch – A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is a data link layer device. The 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.  In other words, switch divides collision domain of hosts, but broadcast domain remains same.

6. Router – 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.

7. Brouter – It is also known as bridging router is a device which combines features of both bridge and router. It can work either at data link layer or at network layer. Working as router, it is capable of routing packets across networks and working as bridge, it is capable of filtering local area network traffic.

Some hybrid network devices:

Multilayer Switch: a switch which, in addition to switching on OSI layer 2, provides functionality at higher protocol layers.

Protocol Converter: a hardware device that converts between two different types of transmissions, such as asynchronous and synchronous transmissions.

Bridge Router (Brouter): Combine router and bridge functionality and are therefore working on.

Digital media receiver: Connects a computer network to a home theatre

Proxy: computer network service which allows clients to make indirect network connections to other network services

Firewall: a piece of hardware or software put on the network to prevent some communications forbidden by the network policy

Network Address Translator: network service provide as hardware or software that converts internal to external network addresses and vice versa Other hardware for establishing networks or dial-up connections:

Multiplexer: device that combines several electrical signals into a single signal

Network Card: a piece of computer hardware to allow the attached computer to communicate by network

Modem: device that modulates an analog “carrier” signal (such as sound), to encode digital information, and that also demodulates such a carrier signal to decode the transmitted information, as a computer communicating with another computer over the telephone network ISDN terminal adapter (TA): a specialized gateway for ISDN

Line Driver:Device to increase transmission distance by amplifying the signal. It is used in base-band networks only.