Types of networks

 A computer network may span any amount of geographical area. It can be on a table, in a room, in a building, in a city, in a country, across continents or around the world. On the basis of the area covered, computer networks are classified as: 

• PAN - Personal Area Network 

• LAN - Local Area Network 

• MAN - Metropolitan Area Network 

• WAN -Wide Area Network

1 Personal Area Network (PAN) 

PAN is a network of communicating devices (computer, mobile, tablet, printer, etc.) in the proximity of an individual. It can cover an area of a radius with few meters

2 Local Area Network (LAN) 

LAN is a network of computing and communicating devices in a room, building, or campus. It can cover an area of radius with a few meters to a few Kilometers. A networked office building, school or home usually contains a single LAN, though sometimes one building can contain a few small LANs (Like some schools have independent LANs in each computer lab)

LAN can be set up using wired media (UTP cables, coaxial cables, etc.) or wireless media (infrared, radio waves, etc.). If a LAN is setup using unguided media, it is known as WLAN (Wireless LAN)

3 Metropolitan Area Network (MAN) 

MAN is a network of computing and communicating devices within a city. It can cover an area of a few Kilometers to a few hundred Kilometers radius. MAN is usually formed by interconnecting a number of LANs and individual computers. All types of communication media (guided and unguided) are used to set up a MAN. MAN is typically owned and operated by a single entity such as a government body or a large

4 Wide Area Network (WAN) 

WAN is a network of computing and communicating devices crossing the limits of a city, country or continent. It can cover an area of over hundreds of Kilometers in radius. WAN usually contain a number of interconnected individual computers, LANs, MANs and maybe other WANs.

The best known example of a WAN is the Internet. Internet is considered as the largest WAN in the world.

Logical classification of networks 

This classification is based on the role of computers in the network and division falls into two categories: peer-to-peer and client-server.

1 Peer-to-Peer 

A peer-to-peer network has no dedicated servers. Here a number of computers are connected together for the purpose of sharing information or devices. All the computers are considered equal.

2 Client-Server 

The client-server concept is the driving force behind most of the networks. It is similar to going to a restaurant, reading the menu, calling the waiter (server) and then ordering one’s preference from the menu. If the ordered item is available in the restaurant at that time, it is 'served' to whom the order was placed (client), else the request is refused.

Classifications for servers are 

a) File server - A computer that stores and manages files for multiple users on a network. 

b) Web server - A computer dedicated to responding to requests for web pages.

c) Print server - Redirects print jobs from clients to specific printers. 

d) Database server - Allows authorised clients to view, modify and/or delete data in a common database. 

Identification of computers over a network

Once a network has been set up, the nodes can communicate among themselves. But for proper communication, the nodes should be uniquely identifiable.

1 Media Access Control (MAC) address 

A Media Access Control (MAC) address is a universally unique address (12 digit hexadecimal number) assigned to each NIC (Network Interface Card) by its manufacturer. 

This address is known as the MAC address. It means that a machine with an NIC can be identified uniquely through the MAC address of its NIC. 

MAC address of an NIC is permanent and never changes. MAC addresses are 12-digit hexadecimal (or 48 bit Binary) numbers. By convention, 

2 Internet Protocol (IP) Address 

An IP address is a unique 4 part numeric address assigned to each node on a network, for their unique identification. IP address is assigned to each machine by the network administrator or the Internet Service Provider. An IP address is a group of four bytes (or 32 bits) each of which can be a number from 0 to 255.

On a network, the IP address of a machine is used to identify it. IP protocol identifies a machine with its IP address to route the packets.

There are two versions of IP addresses: version 4 (IPv4) and version 6 (IPv6). IPv4 uses 32 bits and IPv6 uses 128 bits for an IP address. Using IPv4 only 232 (approximately 4 billion) distinct devices can be addressed.

As the number of devices which need to be networked (mobile phones, home appliances, personal communication devices, etc.) is increasing at a very fast pace, IPv4 addresses are being exhausted. To address this problem IPv6 was developed and it is now being deployed. Using IPv6, 2128 (approximately 4 billion × 4 billion × 4 billion × 4 billion) distinct devices can be addressed.

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