Routers

Routers are small electronic devices that join multiple computer networks together via either wired or wireless connections.

How Routers Work

In technical terms, a router is a Layer 3 network gateway device, meaning that it connects two or more networks and that the router operates at the network layer of the OSI model.

Routers contain a processor (CPU), several kinds of digital memory,and input-output (I/O) interfaces.

They function as special-purpose computers, one that does not require a keyboard or display.

The router's memory stores an embedded operating system (O/S). Compared to general-purpose OS products like Microsoft Windows or Apple Mac OS, router operating systems limit what kind of applications can be run on them and also need much smaller amounts of storage space.

Examples of popular router operating systems include Cisco Internetwork Operating System (IOS) and DD-WRT. These operating systems are manufactured into a binaryfirmware image and are commonly called router firmware.

By maintaining configuration information in a part of memory called the routing table, routers also can filter both incoming or outgoing traffic based on the addresses of senders and receivers.

Routers for Business Networks and the Internet

Before home networking became popular, routers could be found only the closets of businesses and schools.Each cost thousands of dollars and required special technical training to set up and manage.

The largest and most powerful network routers form the Internet backbone.

 These routers must manage many terabits of data flowing through and between Internet Service Provider (ISP) networks 

Home Broadband Routers

Routers became mainstream consumer devices when households began to accumulate multiple computers and wanted to share the home Internet connection

Home networks use Internet Protocol (IP) routers to connect computers to each other and to the Internet.

 Early generations of home routers supported wired networking with Ethernet cables while newer wireless routers supported Wi-Fi together with Ethernet. The term broadband router applies to any home wired or wireless router being used for sharing a broadband Internet connection.

Home routers often cost USD $100 or less. They are manufactured to be much more affordable than business routers in part because they offer fewer features. Still, home routers provide many essential home networking functions:

• sharing of home Internet connections for dozens of devices
• basic home network firewall and other security support
• ability to change router configuration settings from a Web browsers

Other Types of Routers and Routing Devices

A class of portable Wi-Fi routers called travel routers are marketed to people and families who want to use the functions of a personal router at other locations besides home.

Routing devices called mobile hotspots that share a mobile (cellular) Internet connection with Wi-Fi clients are also available. Many mobile hotspot devices only work with certain brands of cell service.