01-11-2012, 05:45 PM
Handling Selfishness in Replica Allocation over a Mobile Ad Hoc Network
A mobile ad-hoc network (MANET) is a self-configuring infrastructureless network of mobile devices connected by wireless. ad hoc is Latin and means "for this purpose". Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router. The primary challenge in building a MANET is equipping each device to continuously maintain the information (which is referred to as a ‘state’ in this paper) required to properly route traffic. Such networks may operate by themselves or may be connected to the larger Internet. If two mobile nodes are within each other’s transmission range, they can communicate with each other directly; otherwise, the nodes in between have to forward the packets for them.
Mobile ad hoc networks (MANETs) have attracted a lot of attention due to the popularity of mobile devices and the advances in wireless communication technologies. A MANET is a peer-to-peer multihop mobile wireless network that has neither a fixed infrastructure nor a central server. Each node in a MANET acts as a router, and communicates with each other.
In a mobile ad hoc network, the mobility and resource constraints of mobile nodes may lead to network partitioning or performance degradation. Several data replication techniques have been proposed to minimize performance degradation. Most of them assume that all mobile nodes collaborate fully in terms of sharing their memory space. In reality, however, some nodes may selfishly decide only to cooperate partially, or not at all, with other nodes. These selfish nodes could then reduce the overall data accessibility in the network. In this paper, the authors examine the impact of selfish nodes in a mobile ad hoc network from the perspective of replica allocation. The authors term this selfish replica allocation. In particular, the authors develop a selfish node detection algorithm that considers partial selfishness and novel replica allocation techniques to properly cope with selfish replica allocation. The conducted simulations by the authors demonstrate the proposed approach outperforms traditional cooperative replica allocation techniques in terms of data accessibility, communication cost, and average query delay.
Network partitions can occur frequently, since nodes move freely in a MANET, causing some data to be often inaccessible to some of the nodes. Hence, data accessibility is often an important performance metric in a MANET. Data are usually replicated at nodes, other than the original owners, to increase data accessibility to cope with frequent network partitions.
A node would like to enjoy the benefits provided by the resources of other nodes, but it may not make its own resource available to help others. Such selfish behavior can potentially lead to a wide range of problems for a MANET. In this paper, the authors address the problem of selfishness in the context of replica allocation in a MANET, i.e., a selfish node may not share its own memory space to store replica for the benefit of other nodes.