• Affects of queuing mechanisms on RTP traffic: comparative analysis of jitter, end-to-end delay and packet loss

      Epiphaniou, Gregory; Maple, Carsten; Sant, Paul; Reeve, Matthew (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010)
      The idea of converging voice and data into a best-effort service network, such as the Internet, has rapidly developed the need to effectively define the mechanisms for achieving preferential handling of traffic. This sense of QoS assurance has increased due to the enormous growth of users accessing networks, different types of traffic competing for available bandwidth and multiple services running on the core network, defined by different protocols and vendors. VoIP traffic behaviour has become a crucial element of the intrinsic QoS mainly affected by jitter, latency and packet loss rates. This paper focuses on three different mechanisms, DropTail (FIFO), RED and DiffServ, and their effects on real-time voice traffic. Measurements of jitter, end-to-end delay and packet loss, based on simulation scenarios using the NS-2 network simulator are also presented and analyzed.
    • Crochemore sets

      Gibbons, A.; Sant, Paul (College pubications, 2009)
    • Defining minimum requirements of inter-collaborated nodes by measuring the weight of node interactions

      Sotiriadis, Stelios; Bessis, Nik; Huang, Ye; Sant, Paul; Maple, Carsten (IGI Global, 2011)
      This paper focuses on defining the minimum requirements to support the inter-cooperation between various scales, dynamically evolved Virtual Organizations (VOs). This proposed method is able to assign a weighted value to each pair-wise path that each member (node) can select in order to locate neighbouring nodes according to their preferences. The method also takes into account the communication overhead between each node interaction. The weight of each path is to be measured by the analysis of prerequisites in order to achieve a mutually agreed interaction between nodes. Requirements are defined as the least parameters or conditions that a node needs to achieve in order to determine its accessibility factor. The motivation behind this work is the vision of the Critical Friends Community model, which is a suitable topology for interoperable grid environments. The topology suggests that capturing inter-cooperated nodes interactions that can be publicly available could lead to knowledge of neighbouring VO members which, in turn, could be used for facilitating a more effective resource discovery and selection decision.
    • Defining minimum requirements of inter-collaborated nodes by measuring the weight of node interactions

      Sotiriadis, Stelios; Bessis, Nik; Huang, Ye; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010)
      In this paper we are focusing on the minimum requirements to be addressed in order to demonstrate a inter-node communication within a Virtual Organisation (VO) using the method of Self-led Critical Friends (SCF). The method is able to decide paths that a node can choose in order to locate neighbouring nodes by aiming at realizing the overhead of each communication. The weight of each path will be measured by the analysis of prerequisites in order to achieve the interaction between nodes. We define requirements as the least fundamentals that a node needs to achieve in order to determine its accessibility factor. The information gathered from an interaction is then stored in a snapshot, a profile that is made available during the discovery stage.
    • Effects of iterative block ciphers on quality of experience for Internet Protocol Security enabled voice over IP calls

      Safdar, Ghazanfar Ali; Sant, Paul; Epiphaniou, Gregory; Maple, Carsten (IET, 2012)
      Voice over IP (VoIP) is the technology used to transport real-time voice over a packet-switched network. This study analyses the effects of encrypted VoIP streams on perceived Quality of Experience (QoE) from a user's perspective. An in-depth analysis on how the transparent nature of encryption can influence the way users perceive the quality of a VoIP call have been investigated by using the E model. A series of experiments have been conducted using a representative sample of modern codecs currently employed for digitising voice, as well as three of the most commonly used iterative block ciphers for encryption (DES, 3DES, AES). It has been found that the Internet Protocol Security encryption of VoIP strongly relates to the payload sizes and choice of codecs and this relationship has different effects on the overall QoE as measured by the E model, in terms of the way that users perceive the quality of a VoIP call. The main result of this paper is that the default payload shipped with the codecs is not the optimal selection for an increased number of VoIP calls, when encryption is applied and a minimum level of QoE has to be maintained, per call.
    • Encoding minimum requirements of ad hoc inter-connected grids to a genetic algorithm infrastructure

      Sotiriadis, Stelios; Bessis, Nik; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IADIS, 2010)
    • From grids to clouds: a collective intelligence study for inter-cooperated infrastructures

      Sotiriadis, Stelios; Bessis, Nik; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IARIA, 2010)
      Recently, more effort has been put into developing interoperable and distributed environments that offer users exceptional opportunities for utilizing resources over the internet. By utilising grids and clouds, resource consumers and providers, they gain significant benefits by either using or purchasing the computer processing capacities and the information provided by data centres. On the other hand, the collective intelligence paradigm is characterized as group based intelligence that emerges from the collaboration of many individuals, who in turn, define a coordinated knowledge model. It is envisaged that such a knowledge model could be of significant advantage if it is incorporated within the grid and cloud community. The dynamic load and access balancing of the grid and cloud data centres and the collective intelligence provides multiple opportunities, involving resource provisioning and development of scalable and heterogeneous applications. The contribution of this paper is that by utilizing grid and cloud resources, internal information stored within a public profile of each participant, resource providers as well as consumers, can lead to an effective mobilization of improved skills of members. We aim to unify the grid and cloud functionality as consumable computational power, for a) discussing the supreme advantages of such on-line resource utilization and provisioning models and b) analyzing the impact of the collective intelligence in the future trends of the aforementioned technologies.
    • A graph theoretic framework for trust - from local to global

      Traditional approaches to trust, be it in agent-based societies, or within a more theoretical framework often consider trust to be a local phenomenon. Here we propose that trust should be viewed from a global perspective. Our motivation is the area of pervasive computing although we believe that our formal framework applies in many domains. Here we present our framework and formalize it in the form of graph theory. We present some open problems and discuss the wider application of our work.
    • Methodologies to develop quantitative risk evaluation metrics

      Hamid, Thaier K.A.; Maple, Carsten; Sant, Paul (FCS - Foundation of Computer Science, USA, 2012)
      The goal of this work is to advance a new methodology to measure a severity cost for each host using the Common Vulnerability Scoring System (CVSS) based on base, temporal and environmental metrics by combining related sub-scores to produce a unique severity cost by modeling the problem's parameters in to a mathematical framework. We build our own CVSS Calculator using our equations to simplify the calculations of the vulnerabilities scores and to benchmark with other models. We design and develop a new approach to represent the cost assigned to each host by dividing the scores of the vulnerabilities to two main levels of privileges, user and root, and we classify these levels into operational levels to identify and calculate the severity cost of multi steps vulnerabilities. Finally we implement our framework on a simple network, using Nessus scanner as tool to discover known vulnerabilities and to implement the results to build and represent our cost centric attack graph.
    • A mobile agent strategy for grid interoperable virtual organisations

      Sotiriadis, Stelios; Bessis, Nik; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IADIS, 2010)
    • Modelling self-led trust value management in grid and service oriented infrastructures

      Brown, Antony; Sant, Paul; Bessis, Nik; French, Tim; Maple, Carsten (IGI Global, 2010)
      Current developments in grid and service oriented technologies involve fluid and dynamic, ad hoc based interactions between delegates, which in turn, serves to challenge conventional centralised structured trust and security assurance approaches. Delegates ranging from individuals to large-scale VO (Virtual Organisations) require the establishment of trust across all parties as a prerequisite for trusted and meaningful e-collaboration. In this paper, a notable obstacle, namely how such delegates (modelled as nodes) operating within complex collaborative environment spaces can best evaluate in context to optimally and dynamically select the most trustworthy ad hoc based resource/service for e-consumption. A number of aggregated service case scenarios are herein employed in order to consider the manner in which virtual consumers and provider ad hoc based communities converge. In this paper, the authors take the view that the use of graph-theoretic modelling naturally leads to a self-led trust management decision based approach in which delegates are continuously informed of relevant up-to-date trust levels. This will lead to an increased confidence level, which trustful service delegation can occur. The key notion is of a self-led trust model that is suited to an inherently low latency, decentralised trust security paradigm.
    • A resource discovery architecture of loosely coupled grid inter-cooperated virtual organisations using mobile agents and neural networks

      Sotiriadis, Stelios; Bessis, Nik; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010)
      Grid computing offers a service for sharing resources over uncertain and complex environments. In such multi-participated settings it is essential to make the grid middleware functionality transparent to members by providing the ability to act autonomous and learning from the environment. Parallel to grid, artificial neural networks is a paradigm for processing information, which is inspired by the processes of biological nervous systems. The latter fields can be really promoted from the artificial intelligent agents, which offer an autonomous acting infrastructure of members with proactive and reactive aptitude. As grid is about sharing and allocating resources within uncertain domains, intelligent agents and neural networks may be the mean of achieving an autonomous learning environment of self-motivated members. In this study, we focus on the mobility agents' model aiming to discovery resources dynamically, parallel to the artificial neural networks as a way to achieve the best resource discovery paths. Our work is fundamentally based on the Self-led Critical Friends method, a technique for realizing inter-cooperation among various scales Virtual Organisations (VOs). Their mediator acting nature redirects communication to other parties of different VOs by utilizing a public profile of data stored within VO members.
    • Teaching large student cohorts in Second Life

      Conrad, Marc; Pike, David; Sant, Paul; Nwafor, Catherine (INSTICC Press, 2009)
    • Towards decentralized grid agent models for continuous resource discovery of interoperable grid Virtual Organisations

      Sotiriadis, Stelios; Bessis, Nik; Huang, Ye; Sant, Paul; Maple, Carsten; University of Bedfordshire, UK (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010)
      Grid technology enables resource sharing among a massive number of dynamic and geographically distributed resources. The significance of such environments is based on the aptitude of grid members to look across multiple grids for resource discovery and allocation. Parallel to grid, agents are autonomous problem solvers capable of self-directed actions in flexible environments. As grid systems require self-sufficiency, agents may be the means by which to achieve a robust autonomy infrastructure. In this direction we propose a resource discovery method of interoperable grid agents which travel within Virtual Organizations (VOs) and by capturing resource information regarding their action domain; they update the internal data of each grid member. Moreover we propose that resource discovery is a systematic and continually updating process that occurs within a VO and allows information exchange to happen. This exchange takes place between various community members at a pre-defined interval, aiming to distribute internal knowledge about the domain.