A router is an electronic device and/or software that connects at least two networks and forwards packets among them according to the information in the packet headers and routing tables. A routing table is a database in a router that stores and updates the locations (addresses) of other network devices and the most efficient routes to them in order to direct routing. Routing is the process of moving packets across a network from one host to a another.
Part of the job of the routing protocol is to specify how routers report changes and share information with the other routers in the network in order to update their routing tables, thereby allowing networks to dynamically adjust to changing conditions (e.g., changes in network topology and traffic patterns).
Packet routing on the Internet is divided into two main groups: interior routing and exterior routing. The former occurs inside of independent networks, referred to as autonomous systems. The latter are used between the autonomous systems.
There are two main types of algorithms for IP (Internet protocol) routing: distance vector and link state. The former determine best path on the basis of how far the destination is, typically in terms of the number of hops to the destination. The latter use more sophisticated methods taking into consideration link variables such as bandwidth, delay, reliability and load.
Examples of distance vector routing protocols include RIP (routing information protocol) and IGRP (interior gateway routing protocol). Examples of link state protocols are BGP (border gateway protocol), OSPF (open shortest path first), NLSP (NetWare link services protocol) and IS-IS (intermediate system to intermediate system).
Created November 21, 2005.