International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Impact Factor (2012): 3.358 Volume 3 Issue 12, December 2014 www.ijsr.net Licensed Under Creative Commons Attribution CC BY AOMDV- Multipath Routing Protocol in Mobile Networks to Enhance Network Security G. Siva Brindha 1 , M. Rajeswari 2 Department of Computers Science, Hindusthan College of Arts and Science, Coimbatore – 641 028, India Department of Computers Science, Dr. NGP College of Arts and Science, Coimbatore – 641 048, India Abstract: Dynamic topology formed by an interconnection of mobile devices through wireless links is known as Mobile Ad-hoc Network (MANET). It is a dynamic wireless network that can be formulated without the need for any pre-existing infrastructure in which each node can act as a router. Routing protocols play a vital role in transmission of data across the network. The two major classifications of routing protocols are unipath and multipath. One of the main challenges of MANET is the design of robust routing protocol that adapt to the frequent and randomly changing network topology. Passive Attacks such as snooping and Active Attacks such as wormhole attack, black hole attack, byzantine attack, Transport Layer Attacks, Multipath Layer Attacks etc. are possible in the available routing protocols. Wireless ad-hoc networks are unprotected to attacks of the malicious nodes due to security vulnerabilities of the AODV routing protocol. Anonymous routing protocols attract much more attention in secure MANETs for the purposes of security and privacy concerns. The use of AOMDV (Ad-hoc On-demand Multipath Distance Vector) and improved the security of MANET against the several Vulnerabilities is analyzed in this study. Performance of On-demand routing protocols such as Adhoc On-demand Distance Vector (AODV) routing protocol and Adhoc On-demand Multipath Distance Vector (AOMDV) routing protocol are analyzed. AOMDV has better packet delivery ratio and comparatively low average end-to-end delay when compared to the existing AODV protocol. The number of packets dropped in the AOMDV against the vulnerabilities is very low. Thus the proposed technique which uses AOMDV is proved to be better against the attacks. Keywords: AOMDV, AODV, PDR, MANET 1. Overview of AD HOC on-Demand Multipath Distance Vector Routing (AOMDV) The AODV protocol starts a route discovery process through a route request (RREQ) to the destination throughout the network. Once a non-duplicate RREQ is received, the intermediate node records the previous hop and checks for a valid and fresh route entry to the destination. The node sends a route reply (RREP) along with a unique sequence number to the source. On updating the route information, it propagates the route reply and gets additional RREPs if a RREP has either a larger destination sequence number (fresher) or a shorter route found. To eliminate the occurrence of frequent link failures and route breaks in highly dynamic ad hoc networks, AOMDV has been developed from a unipath path on-demand routing protocol AODV. The AOMDV protocol finds multiple paths and this involves two stages which are as follows: 1) A route update rule establishes and maintains multiple loop-free paths at each node, and 2) A distributed protocol finds link-disjoint paths. The AOMDV protocol finds node-disjoint or link-disjoint routes between source and destination. Link failures may occur because of node mobility, node failures, congestion in traffic, packet collisions, and so on. For finding node- disjoint routes, each node does not immediately reject duplicate RREQs. A node-disjoint path is obtained by each RREQ, arriving from different neighbor of the source because nodes cannot broadcast duplicate RREQs. Any two RREQs arriving at an intermediate node through a different neighbor of the source could not have traversed the same node. To get multiple link-disjoint routes, the destination sends RREP to duplicate RREQs regardless of their first hop. For ensuring link-disjointness in the first hop of the RREP, the destination only replies to RREQs arriving through unique neighbors. The RREPs follow the reverse paths, which are node-disjoint and thus link-disjoint after the first hop. Each RREP intersects at an intermediate node and also takes a different reverse path to the source to ensure link-disjointness. The idea behind multipath routing is to look for a multiple routes to a host with the intention of avoiding active attack. There could be a lot of reasons to do this, since it minimizes end-to-end delay in a transfer between two nodes, before the link that they are using disappears. Ad-hoc On-demand Multipath Distance Vector Routing (AOMDV) protocol is an extension to the AODV protocol for computing multiple loop-free and linkdisjoint paths to avoid the active attack. The routing entries for each destination contain a list of the next-hops along with the corresponding hop counts. All the next hops have the same sequence number. This helps in keeping track of a route. For each destination, a node maintains the advertised hop count, which is defined as the maximum hop count for all the paths, which is used for sending route advertisements of the destination. Each duplicate route advertisement received by a node defines an alternate path to the destination. Loop freedom is assured for a node by accepting alternate paths to destination if it has a less hop count than the advertised hop count for that destination. Because the maximum hop count is used, the advertised hop count therefore does not change for the same sequence number. When a route advertisement is received for a destination with a greater sequence number, Paper ID: SUB1532 62