What is a Computer Network?


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A network is a group of interconnected computers, servers , workstations, peripherals connected through communication systems such cables, optical fibers, satellites, radio waves, etc. with the ability of interacting with one another, communicating, organizing data and sharing software, applications and hardware resources. Computer Networks may be classified by their size. Whether the computers and servers in the network are connected within a room, a collge campus, a city, a country or all over the world.

  • Loal area network (LAN) is a network of computers, servers and peripherals confined to a small area such a single room or building or university campus and operated under a single system . Cables and optical fibers are usually used to connect computers, servers and other periphrals.

    Local Area Network Example.

    Fig. 1 - Local Area Network Example

  • Metropoletan Area Network (MAN) is confined to a whole city.

  • Wide Area Network (WAN), ususally covers large geographical areas.

  • Internet: It is the largest network in the world connecting millions of computers and servers from all over the world. Because of the large distances between the computers and servers in the internet, the commuincation between the computers and servers in the internet is done by satelites, undersea cables, optical fibers, etc.

  • Intranet: A private network operated by a large company or institution and which uses internet technolgoies, that is already installed, but can only be accessed by members of the company or the institution.

  • Extranet: It is an intranet that can be accessed by authorized people outside the company owning the intranet.

Networking Devices

  • Hub: it is a connecting device that broadcast data to all devices connected to it.

  • Switch: it is a selective connecting device that send data to devices with a specific IP address.

  • Router: it allows communications between two networks. You need a router at home in order to connect to the internet. The onnection is between your home network and the internet; two networks.

  • Network Interface Card (NIC): it is the device in your computer that sends and receive data.

Rate of Data Transfer

In cable networks, data is transferred one bit a a time; this is called serial data transfer. Data is tranfered over netwrok cables at a certain rate (speed) given as bits per second; for example: 100 bps (or bit/sec) means that 100 bits ( 1's and 0's) are transfered in one second.

IP address

Most devices in a network have an IP (internet protocol) address that identifies a given device (computer, server, etc.) so that it can send and recieve data. A typical IP address is It is made up of 4 parts and has the form dddd.dddd.dddd.dddd where d is a digit that can takes a value between 0 and 9 inclusive and dddd takes values from 0 to 255 corresponding to the 8-bit binary number 11111111.

Books and References
1 - Computer Networking: A Top-Down Approach (6th Edition) 6th Edition - James F. Kurose and Keith W. Ross - ISBN-10: 0132856204
2 - Computer Networks (5th Edition) 5th Edition - Andrew S. Tanenbaum and David J. Wetherall - ISBN-10: 0132126958