  Mobile ad hoc network (MANET) is a collection of wireless mobile nodes. It
dynamically forms a temporary network without using any pre existing network
infrastructure or centralized administration i.e. with minimal prior planning.
All nodes have routing capabilities and forward data packets to other nodes in
multi-hop fashion. As the network is dynamic, the network topology continuously
experiences alterations during deployment. The biggest challenge in MANETs is
to find a path between communicating nodes. The considerations of the MANET
environment and the nature of the mobile nodes create further complications
which results in the need to develop special routing algorithms to meet these
challenges. Swarm intelligence, a bio-inspired technique, which has proven to
be very adaptable in other problem domains, has been applied to the MANET
routing problem as it forms a good fit to the problem. In ant societies the
activities of the individuals are not regulated by any explicit form of
centralized control but are the result of self-organizing dynamics driven by
local interactions and communications among a number of relatively simple
individuals. This unique characteristic has made ant societies an attractive
and inspiring model for building new algorithms and new multi-agent systems. In
this paper, we have studied and reviewed Ant Colony based routing algorithms
and its variants. Finally, a performance evaluation of the original ARA and the
EARA is carried out with respect to each other.
