Mobile Ad-Hoc Network (MANET) is network of wireless communication, dynamic topology, limited resources and lack of centralized administration. MANETs are vulnerable to various types of Denial of Service (DoS) attack on network layer. In Gray hole and Black hole attacks malicious nodes deliberately disturb data transmission in the network by sending incorrect routing information. It is a challenge to keep the communication route free from such attackers. The purpose is to characterize and compare the popular DoS attack used by the attackers in recent times, One major DOS attack against the Optimized Link State Routing protocol (OLSR) known as the node isolation attack occurs when topological knowledge of the network is exploited by an attacker who is able to isolate the victim from the rest of the network and subsequently deny communication services to the victim. In this thesis, we suggest a novel solution to defend the OLSR protocol from node isolation attack by employing the same tactics used by the attack itself.
WORM Hole, Grey Hole, MANET, MPLS, Routing Layer.