A router is a networking device whose software and hardware are usually tailored to the tasks of routing “ selecting paths in a network along which to send network traffic ” and forwarding information “relaying of packets from one network segment to another by nodes in a computer network“.

The router is the only device that sees every message sent by any computer on either of the networks .

Router is extremely useful in dealing with two separate computer networks. It joins the two networks, passing information from one to the other and, in some cases, performing translations of various protocols between the two networks. It also protects the networks from one another, preventing the traffic on one from unnecessarily spilling over to the other.

One of the tools a router uses to decide where a packet should go is a configuration table. A configuration table is a collection of information, including:

• Information on which connections lead to particular groups of addresses
• Priorities for connections to be used
• Rules for handling both routine and special cases of traffic

Configuration table is very useful that make sure :

• The router ensures that information doesn’t go where it’s not needed. This is crucial for keeping large volumes of data from clogging the connections of “innocent bystanders.”
• The router makes sure that information does make it to the intended destination.

Wi-Fi is a trademark of the Wi-Fi Alliance ,the Wi-Fi Alliance tests the wireless components to their own terms of reference becouse of incompatibilities between products from different manufacturers. Products that pass become Wi-Fi certified and may carry the Wi-Fi logo. Only products of Wi-Fi Members are tested, because they pay membership and per-item fees. Absence of the Wi-Fi logo does not necessarily mean non-compliance with the standard.

Different competitive brands of access points and client network interfaces are inter-operable at a basic level of service. Products designated as “Wi-Fi Certified” by the Wi-Fi Alliance are backwards compatible. Wi-Fi is a global set of standards. Unlike mobile telephones, any standard Wi-Fi device will work anywhere in the world.

A Wi-Fi enabled device such as a PC, game console, mobile phone, MP3 player or PDA can connect to the Internet when within range of a wireless network connected to the Internet.

Wi-Fi allows local area networks (LANs) to be deployed without wires for client devices, typically reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.

Wireless network adapters are now built into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices. Wi-Fi has become widespread in corporate infrastructures.

How wireless network works :

1. A computer’s wireless adapter translates data into a radio signal and transmits it using an antenna.
2. A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection.

A wireless router allows you to use wireless signals or Ethernet cables to connect your computers to one another, to a printer and to the Internet. Most routers provide coverage for about 100 feet (30.5 meters) in all directions, although walls and doors can block the signal. If your area  is very large, you can buy inexpensive range extenders or repeaters to increase your router’s range.

As long as they all have wireless adapters, several devices can use one router to connect to the Internet. This connection is convenient, virtually invisible and fairly reliable; however, if the router fails or if too many people try to use high-bandwidth applications at the same time, users can experience interference or lose their connections.