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To understand how networks work, it is necessary to learn about different kinds of networks and certain terminologies associated with them.
Local Area Network
When two or more computers are connected with the help of network cards and cables, a Local Area Network or LAN is created. All computers on this network can access shared files, folders and other shared resources such as printers and an Internet connection.
Wide Area Network
When two or more LANs are connected, a Wide Area Network or WAN is created. Often, a WAN is used to connect offices in different locations using leased lines or VSAT (very small aperture terminals) or similar medium. A WAN is a geographically dispersed network of telecommunication.
Internet
Simply put, a network of such WAN networks, which is also publicly accessible using a commonly followed naming system, makes up the Internet. The Internet carries information from a computer in a network to any other computer in another network. Thus, the Internet acts as a common carrier of data. All computers on the Internet communicate via the standard Internet Protocol (IP). The Internet allows users at any computer to procure information (if authorized) from another computer.
Packets
A packet is the unit of data that is routed between an origin and a destination on the Internet. When information is sent from one computer to another on the Internet, the information is broken into packets for efficient routing. Each packet is then given a unique number and is informed of the destination. These packets travel through different routes over the Internet. Once they arrive at their destination, they are reassembled into the original data.
Everything — Web pages, e-mail messages, and downloads — that pass over the Internet are broken down into packets.
Ports and Addresses
Every computer on a network is assigned a unique number called an IP address. The packets are addressed to a specific port at a specific IP address. The IP address directs the packets to reach their destinations. The IP address performs a dual job. It identifies:
Each application that sends and receives data over the network is assigned a special port number. When a particular port receives packets of information, the computer knows which application gets the packet. For example, port 80 is the port for Web servers that host Web sites, while e-mail uses port 25.
Firewalls
A firewall separates one portion of a network from another and allows only authorized network traffic to pass through.
A firewall can scan packets that pass in and out of the network to ascertain if they are legitimate. In case of suspicious packets, the firewall filters them out. It can also hide the identity of your computer within your network so that predators and hackers are unable to target individual computers.
Servers
A server is a computer system that is attached to a network and provides services to other computing systems. It is used to perform functions such as sharing a printer, storing files, or delivering Web pages.
Many servers are dedicated to a specific role. For instance, a 'file server' is a computer and storage device dedicated to storing files. Any user on the network can store files on the file server. A 'print server' manages one or more printers.
Some servers may also be used for other purposes. A person in the office, for example, may use a large desktop computer as a desktop whereas other computers may use it as a server.
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