Routers

A router is a microprocessor-controlled device that transmits data packets across different computer networks. There are different types of routers. The best known type are home and office routers that merely pass data like email and web pages between home computers and DSL or cable modems. Another type of router are enterprise routers, which are typically used by ISPs or large businesses. A third type are core routers, which are used to along the high speed lines of the Internet's backbone.

Much like a traffic officer directs traffic at a busy intersection, a router directs data transmissions. In order to function, a router must be connected to at least two data lines from different networks, such as the local area network you have at home and the Internet. When a packet arrives, the router reads the addressing information included in order to figure out where the packet will ultimately end up. Then, it uses a routing table to find the best network onto which to forward the packet.

Another function of a router is translation. Different networks can use different protocols for data transmission. If the next network uses a different protocol, part of the job of the router is to translate the protocol of the packet for the new network before passing it on.