On-demand routing protocols
Another in the family of routing protocols for mobile ad-hoc network is on-demand routing protocols. With on-demand protocols, if a source node requires a route to the destination for which it does not have route information, it initiates a route discovery process which goes from one node to the other until it reaches to the destination or an intermediate node has a route to the destination.

It is the responsibility of the route request receiver node to reply back to the source node about the possible route to the destination. The source node uses this route for data transmission to the destination node. Some of the better known on-demand protocols are Ad-hoc On-demand Distance Vector routing (AODV), Dynamic Source Routing (DSR) and Temporary Ordered Routing Algorithm (TORA).

These protocols differ on storing the previously known route information and on how they use the established route data. Again, in a network with many participating nodes we may suffer with same sort of problems what we have seen in table-driven protocols.

Conclusion
In conclusion, routing is one of the core issues in mobile ad-hoc network. An effective routing mechanism will be helpful to extend the successful deployment of mobile ad-hoc networks. Current routing protocols provide routing solutions up to a certain level, but are lacking the ability to handle other related issues.

Moreover most of these protocols have designed and implemented on small scale. If these protocols could be extended further by taking into accounts other routing related factors we may come out with a standard routing solution for mobile ad-hoc network.

Jason Perlow is a ZATZ Senior Technical Editor. When he's not recompiling his Linux kernel or scouring the net for great Linux software, he can be reached at perlow@hotmail.com.