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Abstract: Rapid advances in sensor technology and wireless communications have led to the development of wireless sensor networks (WSNs). However, the sensor nodes in WSNs have a finite lifetime since it is often impractical, or even impossible, to recharge their batteries once they have been deployed. When the energy of a sensor node has been fully consumed, it can play no further role within the WSNs. In an attempt to prolong the lifetime of WSNs, various schemes have been proposed. This paper proposed a lifetime-extension under uniform distribution (LEUD) scheme which not only prolongs the lifetime of WSNs, but also optimizes its performance by maximizing the total number of active regions within the networks. To evaluate the effectiveness of our scheme, we chose three uniform distribution algorithms with LEUD to analyze and compared the performance of our scheme. Numerical simulations are performed which demonstrate that when the deployed sensor nodes have an equal initial energy and are distributed uniformly within the networks, LEUD provides an improved networks performance. [Copyright &y& Elsevier]

Abstract: DHCP starvation attack is an attack that targets DHCP servers whereby forged DHCP requests are crafted by an attacker with the intent of exhausting all available IP addresses that can be allocated by the DHCP server. Under this attack, legitimate network users can be denied service. In this paper, we describe the seriousness of the attack and survey and evaluate existing solutions designed to mitigate such an attack. In addition, we propose a novel mitigation solution. Our solution overcomes the limitations of existing solutions in terms of performance, effectiveness, and flexibility. Our solution is based on dynamic fair allocation of IP addresses and is suitable for unshared and shared (wireless) access networks. We study and analyze the proposed mitigation technique through numerical examples and simulations. Furthermore, simulation results show that our proposed solution is far superior in mitigating DHCP starvation attack when compared to other existing techniques such as fixed allocation and DHCP request rate detection. [Copyright &y& Elsevier]