In this paper we are presenting the comparison of the secure OLSR (Optimized Link State Routing Protocol) in mobile ad-hoc network with other approach. We compare the security from the different approach and their effect on the existing OLSR. Main concern of the paper is the security but also the complexity and the storage is also compare in the different approach. Different approaches uses different cryptography security scheme and trying to provide the security to OLSR routing protocols. We also concern the different possible attacks on the OLSR and check that which security scheme is better to provide the security from the attacks.

The mobile ad-hoc networks are vulnerable to Denial of Service (DoS) attacks. MANET has features like self organizing, working as router as well as host having dynamic topology. In MANET, nodes have limited resources like bandwidth, battery power and storage capacity. Gray hole attack is a kind of denial of service (DoS) attack in mobile ad hoc networks. It is specialized type of black hole attack which changes its state from honest to malicious and vice versa. Gray hole attack is an event that degrades the overall network’s performance by intentional malicious activity. In this paper, it is proposed the mechanism against gray hole attack and improves the network performance interms of throughput, packet drop rate, packet delivery ratio and normalized routing overhead.