Agent-based Trusted On-Demand Routing Protocol for Mobile Ad-hoc Networks Islam Tharwat A. Halim 1 , Hossam M. A. Fahmy 2 , Ayman M. Bahaa El-Din 3 , Mohamed H. El-Shafey 4 Department of Computers and Systems Engineering Ain Shams University Cairo, EGYPT islamhalim@yahoo.com 1 , hossam.fahmy@ieee.org 2 , ayman.bahaa@eng.asu.edu.eg 3 , elshafey@gmail.com 4 Abstract— The routing performance in Mobile Ad-hoc Networks (MANETs) relies on the co-operation of the individual nodes that constitute the network. The existence of misbehaving nodes may paralyze the routing operation in MANETs. To overcome this behavior, the trustworthiness of the network nodes should be considered in the route selection process combined with the hop count. The trustworthiness is achieved by measuring the trust value for each node in the network. In this paper, a new protocol based on self monitoring (agent-based) and following the dynamic source routing (DSR) algorithm is presented. This protocol is called Agent-Based Trusted Dynamic Source Routing (ATDSR) Protocol for MANETs. The objective of this protocol is to manage trust information locally with minimal overhead in terms of extra messages and time delay.. This objective is achieved through installing in each participated node in the network a multi-agent system (MAS). MAS consists of two types of agents: monitoring agent (MOA) and routing agent (ROA). A new mathematical and more realistic objective model for measuring the trust value is introduced. This model is weighted by both number and size of routed packets to reflect the “selective forwarding” behavior of a node. The performance evaluation via simulation shows that our protocol is better than standard and trusted DSR. The simulation is done over a variety of environmental conditions such as number of malicious nodes, host density and movement rates. Index Terms— Agent, DSR, MANETs, Routing, Trust I. INTRODUCTION Mobile ad-hoc networks (MANETs) are a collection of mobile nodes which communicate with each other via multi- hope wireless links. Each node in MANETs acts as host and router at the same time. MANETs routing protocols are classified into two categories, table-driven (proactive) and on- demand (reactive) [21]. On-demand routing protocols which are considered in this paper perform better with significantly lower overheads than table- driven routing protocols in many situations. Several ad-hoc on demand routing protocols have been proposed, for example, ad-hoc on demand distance vector AODV [1], dynamic source routing DSR [2], temporally ordered routing algorithm TORA [3]. In general, both types of routing protocols for MANETs are designed based on the assumption that all participating nodes are fully cooperative. Due to MANETs characteristics such as openness, mobility, dynamic topology and protocol weaknesses, these may be targeted by attackers in a number of ways [4]. Several “secure” routing protocols have been proposed for MANETs [8, 9, and 13]. Most of them assume centralized units or trusted third-parties which actually destroy the self-organization nature of MANETs. These protocols are effective to fight against external attacks, but are not able to prevent selfishness like misbehaviors. For example, a node may refuse to forward data packets for other nodes to save its battery. So a comprehensive approach is necessary for MANETs to prevent both attacks and misbehaviors. This approach is regarding the security improvement of the above mentioned protocols. This is achieved by developing mechanisms for measuring the trustworthiness of the network nodes. The measure of the trustworthiness of such nodes is through a term called trust level, which results in what is called trusted routing protocols. Many trusted routing protocols have been suggested as an effective security mechanism in MANETs [14, 15 and 16]. In these protocols, measuring the node's trust level is challenging issue due to the characteristics of MANETs. These protocols classified the trust relation as direct and indirect relation. Each node has a direct trust relation with the nodes located inside its communication range (neighbors); the direct trust relation is computed by monitoring the behavior of the neighbors in the routing process. On the other hand, the indirect trust relation is concerned with the other nodes located outside the node’s communication range (non-neighbors); a useful method to compute the indirect trust relation is flooding the network with request messages and waiting replies. Evaluating the direct and indirect trust relation consumes both bandwidth and energy, delays the route discovery process and complicates the routing process due to the additional computational overhead. In this paper, a novel agent-based trusted dynamic source routing protocol (ATDSR) is proposed for MANETs. ATDSR is based on the DSR algorithm. The main objective of this protocol is to manage trust and reputation with minimal overhead in terms of extra messages and time delay. This protocol depends on the self monitoring of each node to find out its trust value. An objective model for measuring the trust value is presented. This object is achieved through installing a multi-agent system (MAS) in each participated node in the network. MAS consists of two types of agents: monitoring agent (MOA) and routing agent (ROA). MOA is responsible for evaluating and maintaining its hosting node trust value. ROA uses this trust information in the routing process. ATDSR in comparison with standard and trusted DSR provides better security with significantly less overhead in terms of extra messages and time delay in finding trusted end- to-end routes. 2010 Fourth International Conference on Network and System Security 978-0-7695-4159-4/10 $26.00 © 2010 IEEE DOI 10.1109/NSS.2010.53 255 2010 Fourth International Conference on Network and System Security 978-0-7695-4159-4/10 $26.00 © 2010 IEEE DOI 10.1109/NSS.2010.53 255