Routing

Routing is the means of discovering paths in computer networks along which information (split up into packets) can be sent. Circuit-based networks, such as the voice telephone network, also perform routing, to find paths for telephone calls through the network fabric. 

Routing is usually directed by routing tables, which maintain a record of the best routes to various network locations in order to keep up with the packet arrival rate. Small networks may involve hand configuration. Large networks involve complex topologies and may change constantly, making the constructing of routing tables very problematic. Automatic routing protocols attempt to solve this problem with dynamically updated routing tables. These are updated intermittently by the routing software, based on information carried by the routing protocol, and allow the network to be nearly autonomous in avoiding network failures and blockages. Routing directs forwarding, the passing of logically addressed packets from their local sub network toward their ultimate destination. In large networks, packets may pass through many intermediary destinations before reaching their destination. The hardware used in routing includes hubs, switches and routers.

Difference between Wired and Wireless Rrouting:-

The concept of link abstraction ie. considering the two connected nodes as a link is not valid in the case of wireless as opposed to the wired systems. This is for the following reasons –

 - This can be zero or close to zero in case of wired networks but in case of wireless this value is much greater than zero. 

 - The neighbouring “links” disturb the transfer of packets in a link. A link can be understood as a connection of the two nodes that are talking to each other. 

 -interference (within a path):- Each link of a wireless network is a half duplex link which means that there will be a two way transmission at the intermediary node. Hence, there will be interference within the link itself. 

 - The medium of transmission in wireless networks is broadcast. This causes the packet to be transmitted over the entire network. In wired networks however it is not transmitted over the entire network.