Wireless Sensor Networks (WSNs) is a major sensing technology that has revolutionized the way information is collected, processed, and used in many smart cities’ applications that rely on sensing technologies for event detection and monitoring. Despite the multiple benefits that such technology offers, the quick depletion of sensors’ battery power represents a major concern, mainly due to the extensive computational tasks and communication operations performed by individual sensors. Indeed, the cost of replacing batteries can be prohibitively expensive, especially when sensors are deployed in areas where access is difficult, in urbanized cities. To extend sensors’ lifetime, this paper proposes a new variant of LEACH protocol named LEACH enhanced with probabilistic cluster head selection (LEACH-PRO). LEACH-PRO introduces several measures to extend WSNs nodes’ lifetime such as cluster head node selection using a probabilistic function based on maximum residual energy and minimum distance to the sink. The obtained simulation results have proven the supremacy of LEACH-PRO over LEACH and direct transmission protocol in terms of the achieved network lifetime and the generated traffic overhead. Most importantly, LEACH-PRO will significantly extend the sensors’ lifetime, which would make this type of deployment more viable in smart city scenarios.

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Session Initiation Protocol (SIP) is widely used as a signaling protocol to support voice and video communication in addition to other multimedia applications. However, it is vulnerable to several types of attacks because of its open nature and lack of a clear defense line against the increasing spectrum of security threats. Among these threats, flooding attack, known by its destructive impact, targets both of SIP User Agent Server (UAS) and User Agent Client (UAC), leading to a denial of service in Voice over IP applications. In particular, INVITE message is considered as one of the major root causes of flooding attacks in SIP. This is due to the fact that an attacker may send numerous INVITE requests without waiting for responses from the UAS or the proxy in order to exhaust their respective resources. Most of the devised solutions to cope with the flooding attack are either difficult to deploy in practice or require significant changes in the SIP servers implementation. Apart from these challenges, flooding attacks are much more diverse in nature, which makes the task of defeating them a real challenge. In this survey, we present a comprehensive study of flooding attack against SIP, by addressing its different variants and analyzing its consequences. We also classify the existing solutions according to the different flooding behaviors they are dealing with, their types, and targets. Moreover, we conduct a thorough investigation of the main strengths and weaknesses of these solutions and deeply analyze the underlying assumptions of each of them for better understanding of their limitations. Finally, we provide some recommendations for enhancing the effectiveness of the surveyed solutions and address some open challenges. Copyright © 2015 John Wiley & Sons, Ltd.

Session Initiation Protocol (SIP) is a widely used protocol for voice and video communication in Internet architecture. Due to its open nature and the lack of robust security mechanisms, SIP is vulnerable to several attacks similar to those existing in Internet infrastructure, such as the flooding attack. An attacker can use any SIP request to launch a flooding attack, leading to severe consequences at either client or server side SIP elements or both of them. In this context, end user's devices are considered more vulnerable to flooding attacks due to their limited capabilities. In this paper, we focus on INVITE flooding attack for which we propose a simple and robust detection scheme. This scheme prevents an attacker from launching an INVITE flood through a transition state table used by the proxy to analyse the incoming INVITE requests and exclude the suspicious ones. Our scheme requires also that the end-user keeps track of the time and IP addresses of each incoming request. Furthermore, we modify the header of the REGISTER request by adding a new field named Critical number which holds the value of maximum number of users or callers that could easily be handled by the end user. Unlike the existing solutions, our scheme does not require any special detection device or firewall at the SIP server. The proposed mechanism has been implemented in SIP Express Router (SER) and the obtained results have confirmed its effectiveness.

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