Mobile Ad-Hoc Routing Protocols: Evaluation of Performance

Mobile Ad-hoc networks (MANETs) are the only plausible choice when there is no infrastructure wireless network or it is too expensive to build one as in remote areas. They have the advantage of being quickly deployable. Routing is needed to find a path between the source and the destination and to forward the packets even if the destination node is out of range of the source node. In ad-hoc networks, high mobility, low bandwidth, and limited computing capability characteristics of mobile hosts make routing of data is one of the most difficult issues. In this paper we are considering the performance evaluation of three routing protocols in Mobile Ad-hoc Networks (MANETs). We have evaluated the effect of speed, TCP types, and maximum queue length for Destination Sequence Distance Vector (DSDV) protocol, Dynamic Source Routing (DSR) protocol, and Ad-hoc On Demand Distance Vector (AODV) protocol. 1. Mobile Ad-hoc Routing Protocols One of the first ad-hoc wireless networks was the packet radio network started by ARPA in 1973[6]. It contained 138 nodes and used IP packets for data transport. This made an easy connection possible to the APRAnet, the starting point of today’s Internet. A variant of distance vector routing protocol was used in this ad-hoc network. In ad-hoc networks there are several challenges. There are asymmetric links which means that routing information collected for one direction is of almost no use for the other direction. Also, redundancy can not be controlled. A high redundancy of links causes a large computational overhead for routing table updates. Furthermore, nodes may interfere and destroy each other. However, interference may help routing as a node can learn the topology with the help of packets it has overheard. Moreover, the greatest problem for routing protocols arises from the highly dynamic topology because the nodes must be able to keep up with the drastically and unpredictably changing in the network topology. Destination Sequence Distance Vector (DSDV), Dynamic Source Routing (DSR), and Ad-hoc On Demand Distance Vector (AODV) are classified under flat ad-hoc routing protocols because all nodes play an equal role in routing and the addressing scheme is flat. DSDV is a flat proactive (or table-driven) protocol. It sets up tables required for routing regardless of any traffic that would require routing functionality. An advantage of a proactive protocol is that it can provide Quality of Service (QoS) guarantees related to connection set-up, latency or other real-time requirements. A disadvantage of a proactive protocol is its overhead in lightly loaded networks. Periodic updates for the routing tables consume the batteries of mobile devices and generate a lot of unnecessary traffic (bandwidth). Both DSR and AODV are flat reactive (or on-demand) protocols. They set up a path between the sender and the receiver only if a communication is waiting. An advantage of a reactive protocol is its scalability