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THREAT AGENTS: WHAT InfoSec OFFICERS NEED TO KNOW?

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S. Vidalis, A. Jones
Modern risk assessment techniques recognize that there is a need to perform a threat assessment in order to identify the threats that a system is facing, and the agents that are able to manifest them. Most of them though do not incorporate the process of identifying and analyzing threat agents. Generally, the defenders of computing infrastructures, having spent their professional lives in the "good" side of the wall, would not recognize the identity of a threat agent even when they discover one. Gathering IDS data and analyzing them is a challenge on its own, but identifying threat agents, and analyzing their attributes is a different game altogether. Is an agent motivated enough to pursue his/her target? Does the agent have the technical capability and the knowledge required to exploit a vulnerability? Do enterprises present any of their vulnerabilities to the rest of the world, hence giving threat agents the opportunity to perform active attacks? These are some of the questions that are being addressed in this paper. Our intention is not to put labels in certain categories of people, rather to try and understand these and stimulate the discussions between all those that have good faith.

MAC PARAMETERS TUNING FOR BEST EFFORT TRAFFIC IN 802.11E CONTENTION-BASED NETWORKS

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L. Scalia, I. Tinnirello, G. Bianchi
This paper deals with the problem of best effort traffic delivery in 802.11e contention-based networks. Differently from most previous paper which focus on the support of quality of service (QoS) requirements, we study the tuning of the access parameters for the best effort traffic. The contribution of this paper is threefold. First, we discuss the coexistence between legacy DCF and EDCA stations, since, for guaranteeing the backward compatibility, the best effort service class defined in EDCA should correspond to the legacy DCF. We show what configurations of the access parameters are closer to the DCF protocol, by taking into account the slightly different backoff rules defined in EDCA. Second, we explore the optimizations that can be performed by dynamically tuning the access parameters, on a per-beacon basis, in the case of homogeneous best effort sources. We propose an effective algorithm able to maximize the system throughput, by adapting the minimum contention window to the network contention level. Finally, we analyze the amount of resources available for best effort traffic in presence of QoS traffic. We show that the dynamic adaptation of the minimum contention window as a function of the channel wasted times can be a valid solution to automatically regulate the best effort offered load in the network.

A STATE-DEPENDENT MULTI-RATE LOSS MODEL OF FINITE SOURCES WITH QOS GUARANTEE FOR WIRELESS NETWORKS

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I. Moscholios, M. Logothetis, M. Koukias,
In this paper, we focus on the computation of Call Blocking Probabilities (CBP) in a single link loss model, where calls come from service-classes of finite sources, as it happens in the environment of wireless/cellular networks. We review the Engset Multirate Loss Model and the Single Retry Loss Model for finite sources, in which blocked calls may immediately retry once to be connected in the system with reduced bandwidth and increased service time requirements. We extend these models to the Single- and Multi-Threshold Model for finite sources (f-MTM), which are state dependent models where calls, prior to being blocked, may adjust their traffic requirements according to a common set of thresholds (or a single threshold), which indicates the occupied bandwidth. The f-MTM does not have a product form solution; therefore we prove approximate but recursive formulas for the CBP calculation. Furthermore we apply in the f-MTM the bandwidth reservation policy (f-MTM/BR), used for QoS guarantee (e.g. CBP equalization among different service-classes). The accuracy of the f-MTM/BR is evaluated by comparing analytical with simulation CBP results. Our final target is to propose a generalization of the above models for bandwidth reservation, which is the Connection Dependent Threshold Model for finite sources (f-CDTM/BR), where service-classes may have their own set of thresholds.

AN APPROACH TO WIRELESS SCHEDULING CONSIDERING REVENUE AND USERS SATISFACTION

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L. Badia, M. Zorzi
Recently, several proposals for wireless scheduling algorithms have been presented, using allocation models focused on users’ subjective perception of the service. The goal of these investigations is to design scheduling policies aimed at satisfying more directly the users’ preference. In this paper, we extend this approach, by studying Radio Resource Management, and in particular the scheduler, considering an original model to represent the behavior of multimedia users. We include charging strategies and users’ reaction to prices, so that qualitative and quantitative economic considerations are directly included. After a brief discussion on how to include both perceived quality and pricing, in order to achieve a user-centric evaluation of the QoS, we show how it is possible to schedule users by applying this model so as to obtain a more efficient resource usage, characterized by both larger users’ appreciation and higher revenue for the service provider.

RECENT TRENDS ON QoS FOR WIRELESS NETWORKED CONTROLLED SYSTEMS

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A. Panousopoulou, G. Nikolakopoulos, A. Tzes, J. Lygeros,
In this paper a survey of the recent trends on Quality of Service (QoS) mechanisms for Wireless Networked Controlled Systems (WiNCS) is presented. Our objective is to provide a comprehensive view of the various components required for sufficient QoS from a “Networked Controlled Systems” point of view. We concentrate on ad–hoc wireless networks, due to their importance for real time control applications. QoS–requirements have two interpretations; to provide the necessary bandwidth for transmission, and to ensure that the delay transmission will be bounded. The present survey paper is an attempt to emphasize in the QoS mechanisms that might provide efficient solutions in control–related applications. The presented QoS mechanisms are categorized with respect to the classical Open Source Interconnection (OSI) Reference Model (RM) Protocol Stack (PS) they are serving; the Physical Layer QoS considerations are introduced, the MAC Sub layer solutions are proposed and Network Layer mechanisms outline the current trends in QoS issues. Although QoS and Networked Controlled Systems is a research field still in its infancy, some interesting control–related applications with QoS considerations are presented in order to integrate the current survey and provide motivation for a QoS control dedicated definition.

BLUETOOTH L2CAP LAYER MODELLING AND PERFORMANCE ANALYSIS

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Pi Huang, A. C. Boucouvalas
As one of the major personal wireless communication technologies, Bluetooth was designed for both voice and data communication at low per-unit costs while consuming little power. In this paper, Bluetooth data communications are considered exclusively and Bluetooth performance at the L2CAP level is investigated. By including the effect of errors, we carry out a comprehensive analysis which leads to the derivation of a precise Bluetooth throughput equation at the L2CAP layer for the first time. Analytical results are subsequently verified by simulation results. Numerical results are presented and used to examine the Bluetooth system performance.

MATHEMATICAL ANALYSIS OF THE PACKET DELAY STATISTICS IN BLUETOOTH PICONETS UNDER ROUND ROBIN POLLING REGIME

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D. Miorandi, A. Zanella, S. Merlin,
Personal Area Network technologies like Bluetooth and its subsequent derivations and evolutions (Bluetooth v1.2, v2.0+EDR) are valid candidates to realize the mobile and pervasive communication paradigm that is considered in several recent research projects. Although the delay performance of the basic Bluetooth network configuration (piconet) has been widely evaluated through numerical simulations, no satisfactory analytical framework has been yet proposed in the literature. In this paper we present an analysis of the packet delay statistic in Bluetooth piconets, for a limited-1 (round robin) polling strategy. The mathematical model proposed in this paper extends the other models presented in the literature by providing more accurate results for a wider range of traffic patterns, under the assumption of a marked Poisson arrival process. Our analysis provides a complete statistical characterization of the packet delay, by means of Laplace-Stieltjes transform, for generic traffic patterns. Furthermore, expressions for the estimation of the average packet delay for unbalanced and asymmetric traffic are derived, thus improving existing results based on the theory of M|G|1 queues with vacations. Such expressions are, however, rather complex. Therefore, we propose an approximation, based on a renewal argument, which leads to a closed-form expression for the access delay statistic. The proposed analysis permits an accurate estimation of the packet delay under a wide range of network load conditions.

EQUALISED DUAL HEADER PULSE INTERVAL MODULATION FOR DIFFUSE OPTICAL WIRELESS COMMUNICATION SYSTEM

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Z. Ghassemlooy, W. O. Popoola, N. M. Aldibbiat,
In this paper, the performance of dual header pulse interval modulation (DH-PIM) employing a linear zero forcing equaliser (L-ZFE) in diffused optical wireless indoor environment is presented. The work is based on the ceiling bounce channel model and the Monte Carlos simulation. A 3-tap L-ZFE is used and the results are compared with unequalised DH-PIM as well as with digital pulse interval modulation (DPIM), pulse position modulation (PPM) and on-off keying (OOK) schemes. The power penalty due to intersymbol interference is presented for each of the signalling techniques. The results presented show that equalisation does reduce the error probability and power requirements of high data rate DH-PIM in a highly dispersive environments.

MINIMUM WEIGHTED PATH RESTORATION PROTOCOL FOR ALL-OPTICAL NETWORKS

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A. Vali Sichania, S. Gazorb, H. T. Mouftah,
This paper proposes a novel dynamic restoration scheme for recovery from link failures in all-optical communication networks. Unlike the existing restoration mechanisms, the proposed scheme does not operate on an end-to-end or a point-to-point basis. Accordingly, it reroutes the traffic of a failed path neither to an alternate disjoint route between the disrupted path’s end nodes nor to a loop between the disconnected link’s end points. Instead, the protocol diverts the traffic to a path which in chorus satisfies two conditions: it minimizes the number of to-be-configured (additional) switches; it minimizes the total number of hops between the disconnected source-destination pair (the path length). Two weighting factors are assigned to switches and links in order to assess all alternate paths and reach a joint solution with the lowest weight. We explain the protocol in details and evaluate its performance in terms of system availability. Our analytical results reveal that the proposed scheme outperforms other dynamic restoration protocols.

A SIMULATION PLATFORM FOR QOS PERFORMANCE EVALUATION OF IEEE 802.11E

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. Floros, D. Skyrianoglou, N. Passas, T. Karoubalis.
This paper describes a simulation platform suitable for the performance evaluation of IEEE 802.11e Quality of Service (QoS) mechanisms. 802.11e is an amendment to the IEEE 802.11 standard, describing the enhancements required for QoS provision. The aim of the platform is to provide a flexible and efficient tool for evaluating important components of 802.11e, such as traffic scheduling algorithms, admission control mechanisms and traffic classification schemes. To demonstrate the use of the platform and reveal its advantages, a case study is included, where two different traffic scheduling algorithms proposed for 802.11e are evaluated.