Basics of network routing. – O. O. Elechi
With the fact that the Internet is a network of networks, it means that packets (Protocol Data Unit of the network layer) have several possible paths to pass through when leaving its source to get to its destination. This was actually the idea of the United States Department of Defence when they developed the first packet switching network known as Arpanet. Their main aim then was that if a node was bombed down by enemies in war times, the administrators in offices and soldiers on war fronts should still be able to communicate because the node that was bombed does not lie on the only access route between the office administrators and soldiers on site. Today in the big Internet, several considerations have to be taken by the network router designer on the rules to be embedded on the router for it to use when routing decisions have to be made on arriving packets. Such considerations include, the least cost to the end router if it has complete knowledge of the topology of the network, the least cost to the nearest neighbour, the least cost to any of its immediate neighbours, manually configured congested links, number of hops and so on. With these considerations several routing algorithms have been designed of which we look at their basic principles.