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Highlights: [•] We proposed prioritized proactive spectrum handoff decision schemes. [•] Proposed schemes are modeled using a preemptive resume priority (PRP) M/G/1 queue. [•] Handoff delay is reduced by the proposed schemes. [ABSTRACT FROM AUTHOR]

Rapid advances in software systems, wireless networks, and embedded devices have led to the development of a pervasive and mobile cyberspace that provides an infrastructure for anywhere/anytime service provisioning in different domains such as engineering, commerce, education, and entertainment. This style of service provisioning enables users to freely move between geographical areas and to continuously access information and conduct online transactions. However, such a high mobility may cause performance and reliability problems during the execution of transactions. For example, the unavailability of sufficient bandwidth can result in failure of transactions when users move from one area (cell) to another. We present a context-aware transaction model that dynamically adapts to the users' needs and execution environments. Accordingly, we develop a new mobility management scheme that ensures seamless connectivity and reliable execution of context-aware transactions during mobility of users. The proposed scheme is designed and developed using a combination of different queuing models. We conduct various experiments in order to show that the proposed scheme optimizes the mobility management process and increases the throughput of context-aware transactions. [ABSTRACT FROM PUBLISHER]

Abstract: With the thriving technology and the great increase in the usage of computer networks, the risk of having these network to be under attacks have been increased. Number of techniques have been created and designed to help in detecting and/or preventing such attacks. One common technique is the use of Network Intrusion Detection / Prevention Systems NIDS. Today, number of open sources and commercial Intrusion Detection Systems are available to match enterprises requirements but the performance of these Intrusion Detection Systems is still the main concern. In this paper, we have tested and analyzed the performance of the well know IDS system Snort and the new coming IDS system Suricata. Both Snort and Suricata were implemented on three different platforms (ESXi virtual server, Linux 2.6 and FreeBSD) to simulate a real environment. Finally, in our results and analysis a comparison of the performance of the two IDS systems is provided along with some recommendations as to what and when will be the ideal environment for Snort and Suricata. [Copyright &y& Elsevier]

Abstract: The IEEE 802.16 standard defines several scheduling classes at MAC layer for preferential treatment of service flows depending on QoS requirements specific to a service flow. In this paper, a new framework has been proposed to solve and address QoS issues for fixed point to multipoint (PMP) 802.16 systems. The proposed framework consists of a uplink scheduler and Call Admission Control (CAC) module. The proposed CAC module interact with the uplink scheduler status and makes its decision based on the scheduler’s queues status. Extensive OPNET simulation demonstrates the effectiveness of the proposed framework. [Copyright &y& Elsevier]

Broadcasting is an essential and effective data propagation mechanism, with several of important applications such as route discovery, address resolution, as well as many other network services. As data broadcasting has many advantages, also causing a lot of contention, collision, and congestion, which induces what is known as "broadcast storm problems". Broadcasting has traditionally been based on the flooding protocol, which simply overflows the network with high number of rebroadcast messages until the messages reach to all network nodes. A good probabilistic broadcasting protocol can achieve higher saved rebroadcast, low collisions and less number of relays. In this paper, we propose a dynamic probabilistic approach that dynamically fine-tunes the rebroadcasting probability according to the number of neighbour's nodes distributed in the ad hoc network for routing request packets (RREQs). The performance of the proposed approach is investigated and compared with the simple AODVand fixed probabilistic schemes using the GloMoSim network simulator under different mobility models. The performance results reveal that the improved approach is able to achieve higher saved rebroadcast and low collision as well as low number of relays than the fixed probabilistic scheme and simple AODV. [ABSTRACT FROM AUTHOR]

The article offers an introduction to a series of articles on performance analysis and enhancements of wireless networks including "DS/CDMA throughput of a multi-hop sensor network in a Rayleigh fading underwater acoustic channel," "Effect of redundancy on the mean time to failure of wireless sensor networks," "EZRP: an enhanced zone-based routing protocol for ad-hoc networks," "Augmenting Reed–Solomon coding with retransmission for error recovery in 3G video broadcasts," "SCTP performance evaluation over heterogeneous networks," "Distributed communication model in hierarchical Infostation systems," "QoS-aware mobile service transactions in a wireless environment," "Modeling and evaluation of congestion control for different classes of network traffic," "Mobility management in hybrid ad-hoc networks and the Internet environment," and "Towards building a conflict-free mobile distributed file system."

Abstract: Analysis of networks of queues under repetitive service blocking mechanism has been presented in this paper. Nodes are connected according to an arbitrary configuration and each node in the networks employs an active queue management (AQM) based queueing policy to guarantee certain quality of service for multiple class external traffic. This buffer management scheme has been implemented using queue thresholds. The use of queue thresholds is a well known technique for network traffic congestion control. The analysis is based on a queue-by-queue decomposition technique where each queue is modelled as a GE/GE/1/N queue with single server, R (R ⩾2) distinct traffic classes and {N = N 1, N 2,…, N R } buffer threshold values per class under first-come-first-serve (FCFS) service rule. The external traffic is modelled using the generalised exponential (GE) distribution which can capture the bursty property of network traffic. The analytical solution is obtained using the maximum entropy (ME) principle. The forms of the state and blocking probabilities are analytically established at equilibrium via appropriate mean value constraints. The initial numerical results demonstrate the credibility of the proposed analytical solution. [Copyright &y& Elsevier]

Credit-based flow control scheme that can be used to support both end-to-end and link-level flow control is becoming increasingly popular in high speed system area networks (SAN), e.g. InfiniBand networks where multiple processor nodes and I/O devices are interconnected using switched point-to-point links. By virtue of such a scheme, the downstream node sends credits to the upstream node indicating the availability of buffer spaces. Upon receiving credits, the upstream node injects packets into the networks. Performance analysis of credit-based flow control scheme plays an important role for the design and optimization of InfiniBand interconnection networks which have been widely used in many high-performance cluster, Grid and P2P computing systems. This study develops a new queueing network model for performance evaluation of credit-based flow control in InfiniBand networks. The performance metrics to be derived include the mean queue length, throughput and response time of the system. Simulation experiments have been used to validate the accuracy of the queueing network model. Results obtained from the analytical model have showed that this model can effectively evaluate the performance of credit-based flow control in InfiniBand networks. [ABSTRACT FROM AUTHOR]

Abstract: Composition of Web services enables collaboration among autonomous business organisations such that they can integrate their services to perform collaborative business activities. It facilitates the development of new services using pre-existing Web services thus reducing development and operational costs. However, the highly distributed, dynamic, and autonomous nature of component Web services gives rise to various issues such as service matchmaking, reliability, availability, security and efficiency. This paper presents a new protocol in order to improve the efficiency of Web services composition. The proposed protocol is based on the peer-to-peer paradigm which exploits the capabilities of underlying networks such that part of the processing is carried out at the network nodes. Efficiency of the proposed protocol is tested through various experiments. Experimental results show that the proposed protocol significantly improves performance by reducing the system response time in the composition of Web services. [Copyright &y& Elsevier]

Many performance models for deterministic routing in multicomputer interconnection networks have been derived and analyzed under the assumption of the traditional Poisson stochastic arrival process, which is inherently unable to capture traffic self-similarity revealed by many real-world parallel applications. In an effort towards understanding the network performance under various traffic loads and different design alternatives, this paper presents an analytical model for dimension-ordered routing in k-ary n-cubes when subjected to self-similar traffic. As the service time, blocking probability and waiting time experienced by a message vary from a dimension to another, the design of such a model for dimension-ordered routing poses greater challenges. The developed analytical model is then used to investigate the efficiency of two different ways to organize virtual channels for deterministic routing and to evaluate the impact of self-similar traffic with various Hurst parameters on network performance. [ABSTRACT FROM AUTHOR]