615 PAPER 26 This paper compares the performance of two on-demand routing protocols
- DSR and AODV. It shows that two protocols have significant performance
differentials, and proposes techniques to improve them.

Two algorithms have the following common and different characteristics;

Common Characteristics:
1. The most important common characteristic of two protocols is that they
   are both reactive. They initiate routing activities on an on demand
   basis.
2. The route recoveries are based on query and reply cycles.
3. The routing information is stored in intermediate nodes.

Different Characteristics;
1. DSR uses a source routing, but AODV uses a table driven routing. As
   a result, DSR can access more routing information than AODV.
2. DSR replies to all route discovery requests, so the source can have
   alternative routes, but AODV replies to only the first one and also
   keeps only one entry in the routing table. 
3. DSR does not use any timer, but AODV uses it. AODV have a mechanism
   to expire old routing information, but DSR does not have such a 
   mechanism.
4. AODV is more conservative than DSR in route deletion. In AODV, a link
   failure information is sent to all nodes, but in DSR, only the upsteam
   nodes of a data packet are notified.

They performed the simulations, for two experiment sets - Varying mobility 
and number of sources and Varying offered load, with four metrics - Packet
delivery fraction, Average end-to-end delay of data packets, Normalized
routing load and Normalized MAC load.
In short, DSR shows better performance in less stressful situations, but
AODV gets better as the situations go stressful. DSR always has less protocol
overhead than AODV. However there are variations with respect to simulation
setting. 

Based on the simulation results, they proposed techniques for two protocols.
For DSR, they proposed a timer scheme to eliminate false routing information.
For AODV, they proposed a source routing scheme to reduce the protocol overhead.

This paper has done similar simulation study as the other paper I have reviewed.
The simulation settings and metrics of this paper is also very well designed as
that paper. One good thing of this paper is that it tries to suggest new schemes
to improve the protocols based on the simulation result.

