Ad hoc networks rely on the cooperation of the nodes participating in the network to forward packets for each other. A node may decide not to cooperate to save its resources while still using the network to relay its traffic. If too many nodes exhibit this behavior, network performance degrades and cooperating nodes may find themselves unfairly loaded. Most previous efforts to counter this behavior have relied on further cooperation between nodes to exchange reputation information about other nodes. If a node observes another node not participating correctly, it reports this observation to other nodes who then take action to avoid being affected and potentially punish the bad node by refusing to forward its traffic. Unfortunately, such second-hand reputation information is subject to false accusations and requires maintaining trust relationships with other nodes. The objective of OCEAN is to avoid this trust-management machinery and see how far we can get simply by using direct first-hand observations of other nodes' behavior. We find that, in many scenarios, OCEAN can do as well as, or even better than, schemes requiring second-hand reputation exchanges. This encouraging result could possibly help obviate solutions requiring trust-management for some contexts.
@cite_0: In military and rescue applications of mobile ad hoc networks, all the nodes belong to the same authority; therefore, they are motivated to cooperate in order to support the basic functions of the network. In this paper, we consider the case when each node is its own authority and tries to maximize the benefits it gets from the network. More precisely, we assume that the nodes are not willing to forward packets for the benefit of other nodes. This problem may arise in civilian applications of mobile ad hoc networks. In order to stimulate the nodes for packet forwarding, we propose a simple mechanism based on a counter in each node. We study the behavior of the proposed mechanism analytically and by means of simulations, and detail the way in which it could be protected against misuse.
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@cite_4: In this paper, we address the problem of service availability in mobile ad-hoc WANs. We present a secure mechanism to stimulate end users to keep their devices turned on, to refrain from overloading the network, and to thwart tampering aimed at converting the device into a "selfish" one. Our solution is based on the application of a tamper resistant security module in each device and cryptographic protection of messages.
Researchers have also investigated means of discouraging selfish routing behavior in ad hoc networks, generally through payment schemes @cite_4 , @cite_0 , @cite_9 . These approaches either require the use of tamper-proof hardware modules or central bankers to do the accounting securely, both of which may not be appropriate in some truly ad hoc network scenarios. In the per-hop payment scheme proposed by Buttyan and Hubaux @cite_0 , the payment units are called nuglets and reside in a secure tamper-proof module in each node. They find that given such a module, increased cooperation is beneficial not only for the entire network but also for individual nodes. We rely on much of their work and likewise use a payment scheme. In our simple chipcount'' mechanism, further described in , each node keeps track of the number of packets it has forwarded for its direct neighbors and expects corresponding willingness from those neighbors to carry its traffic. The scheme can result in unfairness to some hosts, but its simplicity and performance may be appropriate in some scenarios.