Fault-Tolerant Routing in Mobile Ad Hoc Networks

Mobile Ad Hoc Networks (MANETs) are characterized by the cooperative engagement of mobile nodes that constitute networks possessing continuously-changing infrastructures, the absence of centralized network managers, access points, fixed base stations, a backbone network for controlling the network management functions, and the absence of designated routers for making routing decisions. All the nodes in MANETs participate in the routing process by acting as routers for one another. However, for the transmission of data from one node to another, such networks normally require several hops because of the limited wireless transmission range associated with the operation of the mobile nodes [2,7,9]. The above-mentioned characteristics of MANETs, particularly those arising due to the mobility of the nodes, and the continuously-changing network infrastructure, pose several challenges. Due to the continuously changing infrastructure, the routes that were once considered to be the “best” may no longer remain as the “best” at a later time instant. Therefore, one needs to continuously re-compute the routes, implying that in such networks, there is no permanent convergence to a fixed set of routes. Thus, any routing protocol that needs to operate in MANET network environments should take these issues into consideration [2]. Designing routing protocols poses further challenges when one needs to design routing schemes in the presence of adversarial environments in MANET networks. This is the primary focus of this chapter. More specifically, we discuss fault-tolerant routing schemes when the network contains malfunctioning nodes. To motivate this, we observe that most existing MANET protocols were postulated considering scenarios in which all the mobile nodes in the ad hoc network function properly and in an idealistic manner. However, adversarial environments are common in MANET environments, and misbehaving nodes degrade the performance of these routing protocols [11]. The need for fault-tolerant routing protocols was identified to address routing in adversarial environments in the presence of faulty nodes by exploring redundancies in the networks [10,11]. Despite the challenges that we mention above, it is worthwhile to note a few applications of MANETs which have made them popular. One of the popular application domains of