Network Performance investigation in Presence of Multiple Vital Node and IDS in MANET Ghanshyam Prasad Dubey 1 , Prof. Amit Sinhal 2 , Prof. Neetesh Gupta 3 1 M.Tech Scholar, Information Technology, T.I.T, Bhopal, India. 2 Professor of Computer Science & Engineering, T.I.T, RGPV, Bhopal, India. 3 Asstt. Professor of Information Technology, T.I.T, RGPV, Bhopal, India. Abstract — A Mobile Ad Hoc Network (MANET) is a self- organizing, infrastructure less, multi-hop network. The wireless and distributed nature of MANETs poses a great challenge to system security designers. Although security problems in MANETs have attracted much attention in the last few years, most research efforts have been focused on specific security areas, such as establishing trust infrastructure, securing routing protocols, or intrusion detection and response, none of the previous work proposes security solutions from a system architectural view. In this paper we proposed multiple vital links finding technique that finds vital links and then we apply IDS module on these vital links only and analyze network performance in Denial of service attack and IDS time. Our simulation tested through NS-2 and deploys mobile node structure with resultant value. Keywords— AODV, IDS, routing overhead, packet delivery ratio, NS-2, Multiple Vital Links, Throughput. I. INTRODUCTION Ad hoc network is a wireless network without having any fixed infrastructure. Each mobile node in an ad hoc network moves arbitrarily and acts as both a router and a host [1]. A wireless ad-hoc network consists of a collection of "peer" mobile nodes that are capable of communicating with each other without help from a fixed infrastructure. The interconnections between nodes are capable of changing on a continual and arbitrary basis. Nodes within each other's radio range communicate directly via wireless links, while those that are far apart use other nodes as relays. Nodes usually share the same physical media; they transmit and acquire signals at the same frequency band. However, due to their inherent characteristics of dynamic topology and lack of centralized management security, MANET is vulnerable to various kinds of attacks. In these and other applications of ad hoc networking, security in the routing protocol is necessary in order to guard against attacks such as malicious routing misdirection, but relatively little previous work has been done in securing ad hoc network routing protocols. Secure ad hoc network routing protocols are difficult to design, due to the generally highly dynamic nature of an ad hoc network and due to the need to operate efficiently with limited resources, including network bandwidth and the CPU processing capacity, memory, and battery power (energy) of each individual node in the network. Existing insecure ad hoc network routing protocols are often highly optimized to spread new routing information quickly as conditions change, requiring more rapid and often more frequent routing protocol interaction between nodes than is typical in a traditional (e.g., wired and stationary) network. Expensive and cumbersome security mechanisms can delay or prevent such exchanges of routing information, leading to reduced routing effectiveness, and may consume excessive network or node resources, leading to many new opportunities for possible Denial-of- Service attacks through the routing protocol. II. RELATED WORK The security problem and the misbehavior problem of wireless networks including MANETs have been studied by many researchers, e.g., [2], [3], [4], [5]. Various techniques have been proposed to prevent selfishness and misbehavior in MANETs. Here we describe some security mechanism previously done by the researchers. Albers et al. proposed a distributed and collaborative architecture of IDS by using mobile agents [6]. A Local Intrusion Detection System (LIDS) is implemented on every node for local concern, which can be extended for global concern by cooperating with other LIDS. Two types of data are exchanged among LIDS: security data (to obtain complementary information from collaborating nodes) and intrusion alerts (to inform others of locally detected intrusion). In order to analyze the possible intrusion, data must be obtained from what the LIDS detect on, along with additional information from other nodes. Sterne et al. proposed a dynamic intrusion detection hierarchy that is potentially scalable to large networks use clustering. Ghanshyam Prasad Dubey et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 3 (3) , 2012,3879-3883 3879