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Capsule Reviews

Kamareddine, F. — 2009-06-10

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK.

Guest Editorial

Katsaggelos, A. K., Molina, R. — 2009-06-10

Aggregation Dynamics in Overlay Networks and Their Implications for Self-Organized Distributed Applications

Saffre, F., Tateson, R., Halloy, J., Shackleton, M., Deneubourg, J. L. — 2009-06-10

In this paper, we investigate the global self-aggregation dynamics arising from local decision-based rewiring of an overlay network, used as an abstraction for an autonomic service-oriented architecture. We measure the ability of a selected set of local rules to foster self-organization of what is originally a random graph into a structured network. Scalability issues with respect to the key parameters of system size and diversity are extensively discussed. Conflicting goals are introduced, in the form of a population of nodes actively seeking to acquire neighbours of a type different from their own, resulting in decreased local homogeneity. We show that a ‘secondary’ self-organization process ensues, whereby nodes spontaneously cluster according to their implicit objective. Finally, we introduce dynamic goals by making the preferred neighbour type a function of the local characteristics of a simulated workload. We demonstrate that in this context, an overlay rewiring process based purely on local decisions and interactions can result in efficient load-balancing without central planning. We conclude by discussing the implications of our findings for the design of future distributed applications, the likely influence of other factors and of extreme parameter values on the ability of the system to self-organize and the potential improvements to our framework.

Dynamic Selection of a Video Content Adaptation Strategy from a Pareto Front

Sofokleous, A. A., Angelides, M. C. — 2009-06-10

Genetic Algorithms may be used together with Pareto Optimality in the process of selection of a suitable video content adaptation strategy, the former to return best or fittest solutions that have evolved over many generations and the latter to evaluate and rank each generation's solutions against a set of objectives without the need to assign weights to each one. The outcome of this is a Pareto front of optimal strategies, all of which would satisfy the objectives. The distribution of optimal strategies on a Pareto front, however, suggests that there may be a ‘best-fit’ optimal strategy. This article refines the process of selection of an optimal strategy by taking into account this distribution alongside user preferences, video content characteristics and usage history. In order to make the refined process dynamic, it pursues its implementation using Self-Organising Neural Networks.

A Pragmatic Methodology for Testing Intrusion Prevention Systems

Chen, Z., Delis, A., Wei, P. — 2009-06-10

Intrusion prevention systems (IPSs) not only attempt to detect attacks but also block malicious traffic and pro-actively tear down pertinent network connections. To effectively thwart attacks, IPSs have to operate both in real-time and inline fashion. This dual mode renders the design/implementation and more importantly the testing of IPSs a challenge. In this paper, we propose an IPS testing framework termed IPS Evaluator which consists of a trace-driven inline simulator-engine, mechanisms for generating and manipulating test cases, and a comprehensive series of test procedures. The engine features attacker and victim interfaces which bind to the external and internal ports of an IPS-under-testing (IUT). Our engine employs a bi-directional injection policy to ensure that replayed packets are subject to security inspection by the IUT before they are forwarded. Furthermore, the send-and-receive mechanism of our engine allows for the correlation of engine-replayed and IUT-forwarded packets as well as the verification of IUT actions on detected attacks. Using dynamic addressing and routing techniques, our framework rewrites both source and destination addresses for every replayed packet on-the-fly. In this way, replayed packets conform to the specific features of the IUT. We propose algorithms to partition attacker/victim-emanated packets so that they are subjected to security inspections by the IUT and in addition, we offer packet manipulation operations to shape replayed traces. We discuss procedures that help verify the IUT's detection and prevention accuracy, attack coverage and behavior under diverse traffic patterns. Finally, we evaluate the strengths of our framework by mainly examining the open-source IPS Snort-Inline. IPS deficiencies revealed during testing help establish the effectiveness of our approach.

A Location Prediction-Based Reactive Routing Protocol to Minimize the Number of Route Discoveries and Hop Count per Path in Mobile Ad Hoc Networks

Meghanathan, N. — 2009-06-10

We propose a new mobile ad hoc network routing protocol called ‘location prediction-based routing’ (LPBR) to simultaneously minimize the number of route discoveries and hop count of the paths for a source–destination session. During a regular flooding-based route discovery, LPBR collects the location and mobility information of nodes in the network and stores the collected information at the destination node of the route search process. When the minimum hop route discovered through the flooding-based route discovery fails, the destination node attempts to predict the current location of each node using the location and mobility information collected during the latest flooding-based route discovery. A minimum hop Dijkstra algorithm is run on the locally predicted global topology. If the predicted minimum hop route exists in reality, no expensive flooding-based route discovery is needed and the source continues to send data packets on the discovered route; otherwise, the source initiates another flooding-based route discovery. Simulation results indicate that LPBR incurs a significantly reduced number of flooding-based route discoveries, lower hop count per path, smaller route discovery overhead, lower end-to-end delay per packet and higher packet delivery ratio compared with that of the minimum hop-based, stability-based and position-based routing protocols.

Preserving the Fault-Containment of Ring Protocols Executed on Trees

Yamauchi, Y., Masuzawa, T., Bein, D. — 2009-06-10

Reliable and fault-tolerant distributed systems have been attracting more and more attention (see Autonomic Computing Project by IBM, http://www-03.ibm.com/autonomic/). A self-stabilizing protocol is a fault-tolerant protocol that guarantees autonomous recovery from any number of and any type of faults that can affect the data stored locally at some process(es). If the impact of the faults can be contained to the affected process(es) and some of its immediate neighbors, then the protocol is also fault-containing. We present a new method, called causal simulation, which preserves the fault-containing property of ring protocols executed on trees.

The Agreement Problem in Unreliable Scale-Free Networks

Yan, K.-Q., Wang, S.-S., Wang, S.-C. — 2009-06-10

Generally, tasks in a distributed system must reach agreement. This requires a set of processors to agree on a common value even though some components may be corrupt. There have been several significant studies on this agreement problem in regularized network environments such as the fully connected, broadcast and multicast networks. Recently, many large complex networks have emerged displaying a scale-free feature that influences the system to reach a common value in a novel way. This unanimity problem is called Byzantine agreement (BA). The BA problem is one of the most significant problems in designing a fault-tolerant distributed system. Unfortunately, existing BA protocols cannot cope with the new network environment, and the BA problem thus must be revisited. In this paper, a new BA protocol is proposed that adapts to the scale-free network (SFN) environment and derives its limit of allowable faulty components while maintaining the minimum number of message exchanges. The correctness and complexity of this protocol have been proved. It is observed that an SFN in conjunction with the proposed agreement protocol can tolerate the maximum number of faulty components.

TRACEY HO AND DESMOND S. LUN * Network Coding: An Introduction. Cambridge University Press (2008). ISBN 9780521873109. 184 pp. {pound}30/$60. Hardcover.

Geil, O. — 2009-06-10

JOHN E. GIBSON, WILLIAM T. SCHERER AND WILLIAM F. GIBSON * How to do Systems Analysis. Wiley (2007). ISBN-13: 978-0-470-00765-5. {pound}47.50. 360 pp. Hardcover.

Harrin, E. — 2009-06-10

Capsule Reviews

Kamareddine, F. — 2009-04-27

Heuristic-Guided Abstraction Refinement

He, F., Song, X., Gu, M., Sun, J. — 2009-04-27

Model checking has been considered as a promising approach to establish the correctness of systems. Counterexample-guided abstraction refinement is a key strategy for model checking in verification of large-scale systems. State separation problem poses the main hurdle during the refinement. We present two fast heuristics to solve this problem. We prove the effectiveness of our heuristics by both theoretical analysis and experimental results. Experimental results show the promising performance of our approach.

Metrics to Evaluate the Use of Object Oriented Frameworks

e Silva, R. P., Freiberger, E. C. — 2009-04-27

The adoption of object-oriented (OO) framework approach can increase the reuse in software development. To reach this goal, however, a high quality OO framework design is needed. Moreover, an OO framework must be used in a proper way. General principles are proposed for OO framework design and use, but it is difficult to evaluate OO framework design and OO framework use in an objective way. This work proposes metrics for quantifying features of OO frameworks and software developed using them. They are useful for evaluating OO framework use and learning how to use it, using statistical comparison with present software based on specific OO frameworks. Additionally, the metrics produce a feedback for OO framework developers. A set of tools developed for automatic gathering and for browsing this kind of information is presented, as well as experimental results.

On Formalizing and Normalizing Role-Based Access Control Systems

Power, D., Slaymaker, M., Simpson, A. — 2009-04-27

Role-based access control (RBAC) has emerged as the dominant access control paradigm for service-oriented systems, with this dominance being reflected by the popularity of RBAC both with the research community and with information technology vendors. RBAC's dominance was solidified in 2004 when an American National Standards Institute standard for RBAC was approved. In this paper, we consider some of the drawbacks of this standard and show how the formal description technique, Z, has been used to underpin a model of RBAC. The model builds on the work of Li et al. and adopts a modular approach. In particular, we consider the relationships between different types of inheritance within our model. We show our model can be used to define a notion of equivalence between different RBAC systems. Finally, we show how—via our model—a particular RBAC system can be normalized to produce a simpler—but semantically equivalent—representation. We illustrate this process via two examples.

Serum Proteomic Abnormality Predating Screen Detection of Ovarian Cancer

2009-04-27

Ovarian cancer is characterized by vague, non-specific symptoms, advanced stage at diagnosis and poor overall survival. A nested case control study was undertaken on stored serial serum samples from women who developed ovarian cancer and healthy controls (matched for serum processing and storage conditions as well as attributes such as age) in a pilot randomized controlled trial of ovarian cancer screening. The unique feature of this study is that the women were screened for up to 7 years. The serum samples underwent prefractionation using a reversed-phase batch extraction protocol prior to MALDI-TOF MS data acquisition. Our exploratory analysis shows that combining a single MS peak with CA125 allows statistically significant discrimination at the 5% level between cases and controls up to 12 months in advance of the original diagnosis of ovarian cancer. Such combinations work much better than a single peak or CA125 alone. This paper demonstrates that mass spectra from the low molecular weight serum proteome carry information useful for early detection of ovarian cancer. The next step is to identify the specific biomarkers that make early detection possible.

Test Selection for Hierarchical and Communicating Finite State Machines

Ipate, F. — 2009-04-27

State-based languages are widely used for modelling systems that have an internal state, such as communications protocols and embedded control systems. As testing is a vital part of system development, this has led to much interest in testing from finite state machines (FSMs). However, complex systems are seldom designed in one step; usually, the design is constructed gradually, through a process of refinement. In the case of state-based models, this may lead to a hierarchy of machines. Furthermore, some of the components of the hierarchy may exhibit concurrent behaviour. In this paper, we present a method for generating tests for a hierarchical FSM by reusing and refining the tests for the FSM components of the hierarchy. The method is also adapted for testing a system of communicating FSMs, in which the communication is one-directional, from one master to one or more slaves.

UML Modeling of User and Database Interaction

Almendros-Jimenez, J. M., Iribarne, L. — 2009-04-27

In this paper, we will present a design technique for user and database interaction based on UML. User interaction will be modeled by means of UML state diagrams, and database interaction by means of UML sequence diagrams. The proposed design technique establishes how to integrate both diagrams in order to describe the user interface and database interaction of a business software system. A case study of an Internet Book Shopping system will be shown to illustrate the proposal.

Tournament Coding of Integer Sequences

Teuhola, J. — 2009-04-27

A new, simple non-statistical source coding technique for sequences of integers is suggested. The method is based on a tournament scheme, with the sequence arranged into pairs, where maxima (‘winners’) are encoded recursively, and minima are encoded by semi-fixed-length codes using the related maxima to bound the code lengths. In the experiments, tournament coding has outperformed the other non-statistical methods (gamma, delta, Fibonacci and interpolative coding) for uniform distribution of numbers. Also for non-uniform distributions the method is quite competitive.

An Appreciation of Dina St Johnston (1930-2007) Founder of the UK's First Software House

Lavington, S. — 2009-04-27

In the 1950s there was no software industry. Dina St Johnston, who had learned to program whilst working for the computer manufacturer Elliott-Automation, founded Vaughan Programming Services in 1959. The company began to specialise in on-line systems for digital process control at a time when industrial automation was in its infancy. In due course the company developed its own platform-independent, timesharing, mini-operating system (MACE) and, in 1970, the Vaughan 4M microprocessor. Vaughan went on to become specialists in the supply of real time controllers for passenger railways. Dina St Johnston remained an active programmer until 1996.

Appreciation of Professor Colin Tully (1936-2007): Professor of Software Practice, Middlesex University

2009-04-27

Colin was Emeritus Professor of Software Practice at Middlesex University from where he retired only recently. He started his career at LEO Computers in the 1950s later joined me at the London School of Economics as a Research Fellow before moving on to York University, then returned to industry before being recruited by Middlesex University to inter alia oversee their research activities in computer science. He was a significant contributor to our understanding of the role of software in the overall system. Since his retirement he has been one of the most active members of the group of 23 academics who have expressed concern about the NHS NPfIT. He will be greatly missed both as a colleague and friend.

Capsule Reviews

Kamareddine, F. — 2009-03-18

A Predictive Video-on-Demand Bandwidth Management Using the Kalman Filter over Heterogeneous Networks

Huang, C.-M., Lin, C.-W., Lin, X.-Y. — 2009-03-18

In order to adapt the quality of an on-demand video stream over a time-varying bandwidth channel, a network-aware bandwidth estimation and rate control scheme are required. This paper proposes a predictive video-on-demand (VoD) bandwidth management and a feedback-based buffer control scheme for streaming fine granular scalability videos over wired/WLAN/3G networks. The predictive VoD bandwidth management includes two parts: bandwidth estimation and rate adaptation. According to the measured information of packet round-trip-time, loss-rate, delay jitter and received bit-rate, an improved Kalman filter is proposed to predict an available bandwidth recursively, and to determine a proper transmission rate in consideration of buffer fullness of a decoder. The optimal parameters of the Kalman filter, e.g. a transition matrix and error covariances, can be initialized, converged and adapted to characteristics of the current network. In our experiments, distinct network traffic models are simulated in comparison with pathChirp and one Republic of China patent. The corresponding estimation results with respect to network information are also exhibited in the real networks.

Design and Performance Evaluation of a Transport Protocol for Ad hoc Networks

Anastasi, G., Ancillotti, E., Conti, M., Passarella, A. — 2009-03-18

Providing efficient transport services over multi-hop ad hoc networks is a fundamental building block for this wireless technology. The typical approach is modifying transmission control protocol (TCP) to fix one (or a few of) its inefficiency while preserving compatibility with the original protocol. However, a complete solution should include a significant number of modifications, such that the original TCP design is deeply modified. In this paper we explore a different approach. We include the desired modifications to TCP in the design of a new transport protocol [transport protocol for ad-hoc (TPA)]. In this way we are able to blend together these features in a unique design framework, and better control interactions among the different (modified) components. We then compare TCP and TPA through field tests, in terms of throughput and total number of transmitted segments. We consider several possible configurations of the protocol parameters, different routing protocols and various networking scenarios. In all the cases taken into consideration, TPA significantly outperforms TCP. To achieve a more thorough understanding of the TPA behaviour, we compare TPA and TCP also in terms of fairness and scalability (both in static and mobile configurations) over a wide range of representative topologies. To this end, we adopt a simulation approach, which is more suitable to this kind of analysis. Simulation results confirm field tests, and show that TPA is able to outperform TCP with respect to all analysed performance figures.

Supporting the OSGi Service Platform with Mobility and Service Distribution in Ubiquitous Home Environments

Ibrahim, A., Zhao, L. — 2009-03-18

The OSGi service specification defines an open service platform for service delivery, composition and execution in networked environments. The specification, however, is limited to a single java virtual machine (JVM) and does not define the distribution and mobility of services across different OSGi platforms and devices. This paper first revisits the fundamentals of OSGi service distribution, clarifies and defines a terminology for OSGi service mobility and distribution. It then proposes to extend the current OSGi platform with service distribution and service mobility that aim to support three important requirements on ubiquitous applications, namely, spontaneous interoperability, mobility and software adaptability. The paper demonstrates these extensions through several prototype implementations. These extensions are supported through a common framework, which targets at ubiquitous environments and aims to facilitate the construction of OSGi applications that span multiple OSGi platforms, multiple JVMs and multiple devices. In addition, the proposed framework offers two special features: First, it supports automatic contextual management through a virtual global shared space whose content is automatically and dynamically adjusted to reflect the changes in the system and the mobile environment; Second, it supports different OSGi bundle and service mobility paradigms. The proposed framework blurs the distinction between local and remote services, where remote services can be accessed as if they were local, which greatly simplifies application development. We believe existing OSGi platform distribution solutions can also be supported by this framework.

Integrating Wireless Sensors and RFID Tags into Energy-Efficient and Dynamic Context Networks

Lopez, T. S., Kim, D., Canepa, G. H., Koumadi, K. — 2009-03-18

Context-aware systems have traditionally used distributed sensors to gather context information. The unique identity provided by radio frequency identification (RFID) tags could provide additional information to the sensor data. However, the task of matching identity and sensor information in the same context is not trivial. By placing wireless sensor nodes in the same RFID tagged objects, we can build distributed wireless networks that collaborate to produce uniquely identified context. In this paper, we introduce a set of network protocols that dictate the formation of context-specific wireless sensor networks (WSNs). One of the main goals of our protocols is to maintain an energy-efficient WSN, in which network members can join and leave the network in a dynamic, transparent way. Simulations show that our design provides important improvements in network lifetime and that it is specially suited for dynamic environments. Additionally, we describe our implementation experience and provide a set of tools for creating and evaluating our application.

Optimal Algorithms for Finding a Trunk on a Tree Network and its Applications

Li, Y., Peng, S., Chu, W. — 2009-03-18

Given an edge-weighted tree T, a trunk is a path P in T which minimizes the sum of the distances of all vertices in T from P plus the weight of path P. In this paper, we give efficient algorithms for finding a trunk of T. The first algorithm is a sequential algorithm which runs in O(n) time, where n is the number of vertices in T. The second algorithm is a parallel algorithm which runs in O(log n) time using O(n/log n) processors on the EREW PRAM model. We present an application of trunk on mobile ad hoc networks for efficient multicasting.