Roberta Daidone

On experimentally evaluating the impact of security on IEEE 802.15.4 networks

IEEE 802.15.4 addresses low-rate wireless personal area networks, enables low power devices, and includes a number of security provisions and options (the security sublayer). Security competes with performance for the scarce resources of low power, low cost sensor devices. So, a proper design of efficient and secure applications requires to know the impact that IEEE 802.15.4 security services have on the protocol performance. In this paper we present the preliminary results of a research activity aimed at quantitatively evaluating such impact from different standpoints including memory consumption, network performance, and energy consumption. The evaluation exploits a free implementation of the IEEE 802.15.4 security sublayer.

IEEE 802.15.4 and ZigBee as Enabling Technologies for Low-Power Wireless Systems with Quality-of-Service Constraints

This book outlines the most important characteristics of IEEE 802.15.4 and ZigBee and how they can be used to engineer Wireless Sensor Network (WSN) systems and applications, with a particular focus on Quality-of-Service (QoS) aspects. It starts by providing a snapshot of the most relevant features of these two protocols, identifying some gaps in the standard specifications. Then it describes several state-of-the-art open-source implementations, models and tools that have been designed by the authors and have been widely used by the international community. The book also outlines the fundamental performance limits of IEEE 802.15.4/ZigBee networks, based on well-sustained analytical, simulation and experimental models, including how to dimension such networks to optimize delay/energy trade-offs.

Experimental evaluations of security impact on IEEE 802.15.4 networks

During these last years, IEEE 802.15.4 [1] has been asserting itself as one of the most promising standards for Wireless Sensor Networks (WSNs). It includes a security sublayer which provides a number of operations and procedures aimed at securing network communications. In spite of the strong interest for the standard from the academic community, so far not so many research works have considered IEEE 802.15.4-2006 security services and their impact on performance. We have realized an open-source implementation of the IEEE 802.15.4 security sublayer, by means of which we aim at evaluating security costs experimentally, with real hardware under realistic conditions.

On evaluating the performance impact of the IEEE 802.15.4 security sub-layer

Nowadays, wireless sensor networks (WSNs) are used in a wide range of application scenarios ranging from structural monitoring to health-care, from surveillance to industrial automation. Most of these applications require forms of secure communication. On the other hand, security has a cost in terms of reduced performance. In this paper we refer to the IEEE 802.15.4 standard and investigate the impact of the 802.15.4 security sub-layer on the WSN performance. Specifically, we analyze the impact that security mechanisms and options, as provided by the standard, have on the overall WSN performance, in terms of latency, goodput, and energy consumption. To this end, we develop an analytical model and a security enabled simulator. We also use a real testbed, based on a complete open-source implementation of the standard, to validate simulation and analytical results, as well as to better understand the limits of the current WSN technology.

Models and Tools

An accurate planning and dimensioning of the network parameters and resources is paramount for the overall system to behave as expected. This is particularly important when there are more demanding quality-of-service requirements to be met, namely related to the correct and timely execution of the tasks and transmission of messages. This chapter outlines a set of analytical and simulation models and tools to help the system designer to setup and fine tune all relevant settings and parameters, as well as to anticipate hardware problems and identify the network behavior and its performance limits.

A solution to the GTS-based selective jamming attack on IEEE 802.15.4 networks

The IEEE 802.15.4 standard allows devices to access the medium not only in contention mode but also in a contention-free way, in order to support quality of service (QoS). In contention-free mode, devices access the medium according to the guaranteed time slot (GTS) mechanism, which is vulnerable to the selective jamming attack. This is a particularly insidious form of denial of service that allows an attacker to thwart QoS while limiting her own exposure at the minimum. In this paper, we present selective jamming resistant GTS , a solution against the GTS-based selective jamming. We also show that our solution is standard compliant and affordable for resource-scarce devices like Tmote Sky motes.

IRIS: Efficient Visualization, Data Analysis and Experiment Management for Wireless Sensor Networks

The design of ubiquitous computing environments is challenging, mainly due to the unforeseeable impact of real-world environments on the system performance. A crucial step to validate the behavior of these systems is to perform in-field experiments under various conditions. We introduce IRIS, an experiment management and data processing tool allowing the definition of arbitrary complex data analysis applications. While focusing on Wireless Sensor Networks, IRIS supports the seamless integration of heterogeneous data gathering technologies. The resulting flexibility and extensibility enable the definition of various services, from experiment management and performance evaluation to user-specific applications and visualization. IRIS demonstrated its effectiveness in three real-life use cases, offering a valuable support for in-field experimentation and development of customized applications for interfacing the end user with the system.

Energy-Efficiency in Data Centers

Moving from a still on-going work [1], this section reports the progress being developed towards energy-efficient operations and the integrated management of cyber and physical aspects of data centers. In particular, an integrated system composed by wired and wireless sensors is presented: it monitors power consumptions of the servers and environmental conditions, with the goal of achieving an overall reduction of data centers’ energy consumptions. As like as the EMMON system ( Chap. 8), the architecture proposed is intended to be hierarchical, modular and flexible enough to achieve high temporal and spatial resolution of the sensor measurements, with negligible latencies of sensors’ reports to the data center management control station.Overall, the advantage of having fine-grained power and environmental measurements in this application scenario is twofold: (i) measuring the power consumption at the single server level has enormous benefits for the business logic of data centers’ owners, since they can offer services and billing to their customers based on the actual consumption, and (ii) although there are in literature models to predict heat-flows used in commercial Computer Room Air Cooling (CRAC) systems, those models often lack of spatial resolution, so the availability of micro-climate conditions would help improving those models as well as continue feeding them with real data will improve the reliability and accuracy of their forecasts. Fine-grained measurements are also the basis to provide different views of the system, each of them customized to different users. The proposed architecture allows to set the desired resolution of the readings upon user’s requests, for example to investigate some problems in a specific area (row, room or floor) of the data center building. Every single sensor can be configured by setting user defined alarms and trigger measurements reports adaptively, by changing or (re-)configuring specific thresholds at run-time.

Amendments to the IEEE 802.15.4 Protocol

This chapter presents specific amendments to the IEEE 802.15.4, so that some of the open issues that have been previously identified. In particular, a new implicit GTS allocation mechanism (i-GAME) is proposed that over performs the default one. Then, a node grouping mechanism (H-NAMe) is proposed so that the hidden nodes problem is mitigated and consequently energy-efficiency, throughput and latency are improved. Also, we present a very simple mechanism to exploit differentiate the traffic based on multiple priority. Finally, an overview of several improvements affecting the security and privacy of the messages against external attacks and spoofing is presented. Importantly, all these mechanisms have been implemented and integrated in the 15.4 protocol stack and experimentally validated.

A performance evaluation method for WSNs security

The amount of Wireless Sensor Network applications requiring security is getting higher and higher and also developers that are not security experts are often required to secure their applications. Many times they do it without any consciousness of the security performance trade-off arisen by this operation.In this paper we present a method for performance evaluation of a modular security architecture for WSNs. Our method evaluates the costs that have to be paid when introducing security, in terms of memory occupancy, network performance and energy consumption. Knowing these indexes leads to awareness of security costs and helps in fine tuning of security performance trade-offs. A designer may apply our method to know the impact on performance of the security modules he needs. Also, we present performance data collected by applying our method on the implementation of PLASA, a modular security architecture we have designed and evaluated.