Routing protocols for existing networks have not been designed specifically to provide the kind of dynamic,
self-starting behavior needed for ad-hoc networks.
Most protocols exhibit their least desirable behavior when presented with a highly dynamic interconnection topology. Although we thought that mobile computers could naturally be modeled as routers,
it was also clear that existing routing protocols would place too heavy a computational burden on each mobile computer. Moreover, the convergence characteristics of existing routing protocols did not seem good enough
to fit the needs of ad-hoc networks.
Lastly, the wireless medium differs in important ways from wired media, which would require that we make
modifications to whichever routing protocol we might choose to experiment with.
For instance, mobile computers may well have only a single network interface adapter, whereas most existing routers have network interfaces to connect two separate networks together, Besides, wireless media are of limited and variable range, in distinction to existing wired media.
Since we had to make lots of changes anyway, we decided to follow our ad-hoc network model as far aa we could and ended up with a substantially new approach to the classic distance-vector routing.