Computer Network

What is a Computer Network?
A computer network may be defined as the coordination or interconnection of a number of individual computers. A computer network is basically established by the network layer in the Open Systems Infrastructure model, popularly known as the OSI model.

Classifications
Computer networks can be classified by means of a lot of types like the network size, structure, mode of connectivity, topology and others. Some of them are,

Network Size
Considering the size of the implemented network, Computer networks are classified into 3 main divisions namely Local Area Network (LAN), Wide Area Network (WAN) and Metropolitan Area Network (MAN). In certain fields, they are also further classified into Personal Area Network (PAN), Campus Area Network (CAN) and Global Area Network (GAN).

LAN: - A network of computers which cover only a small area like an office or a building can be referred to as a Local Area Network. All the individual computers must have a common protocol layer for their connectivity with the basic functionality taking place at the network layer. In general, LANs are based on Ethernet technology.

WAN: - Wide Area Network is basically an extension of the Local Area Network except for the fact that the size of the network extends to a very large area. The major functionality of the WAN networks take place at the 3 lower layers of the OSI model namely network layer, data link layer and the physical layer.

MAN: - Metropolitan Area network is a combination of two or more individual Local Area Networks but with a small criterion of the boundary of the network not exceeding the city limits, thus integrating the network as a single unit within a city.

PAN: - Personal network is the smallest of all networks with most of the networks not exceeding a total size of 25 feet.

CAN: - This is similar to a wide area network but the size of the network is limited to a certain social limit, for example the network in an university where the total network is formed by the collaboration of more than one Local Area Network.

GAN: - Global Area Networks are large scale WANs and are implemented globally. The total network consists of a large number of sub-networks with most of the connectivity between the networks is done using wireless networks.

Structure Of The Network
Considering the structure and relationship between the elements of a computer network, the network may be classified into 3 divisions namely Client-Server model, Peer to Peer model and Active Networking model. Each of the classifications has a separate and unique structure which differentiates them in connectivity and working mode.

Mode of Connectivity
By means of the connection mechanisms, computer networks are divided into wired networks and wireless networks. The wired networks are further divided into some sub-divisions like Optical Fiber and Ethernet networks.

Topology
In general, a computer network is technically classified based on the topology of the total network which includes the structure of the networks too. They are divided into Bus networks, Ring network, Star network, Mesh network, Star-bus network, Tree network.

Hardware Requirements for a Network Set-Up
Other than the computers required for a network establishment, the requirement arises for other hardware components too. Some of them are,

Routers
Routers simply function as an intermediary device which forwards the data packets that it receives, to the next available or neighboring router or a terminal.

Switches
Switches are the virtual controllers of routers and bridges. These are operated from each of the individual layers of the OSI layer. Certain cases where the devices operate on multiple layers are called multilayer switch.

Bridges
Technically, a bridge acts a connector between the data link layer and the network layer. The three types of bridges are Local Bridges, Remote Bridges and Wireless bridges.

Network Cards
Network cards are the most important hardware component of a computer network. The most important functionality of the layer is to enable communication between the computers in a network.