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Garofalakis J.,University of Patras | Garofalakis J.,Research Academic Computer Technology Institute | Stergiou E.,ATEI of Epirus
International Journal of Parallel, Emergent and Distributed Systems | Year: 2011

In this paper, a discrete-time, single server with parallel multi-buffers, switching element (SE) is presented and analysed. This SE is used in the construction of multistage interconnection networks which have the ability to service the multi-priority traffic-supporting good quality of service. Through a queuing analysis and under various values of multi-traffic classifications, a performance evaluation is determined. This analytical model is based on the steady-state description of the system behaviour. An utilisation's formula is extracted by considering the steady state of the discrete-time multistage network. Consequently, we estimated the rest of the performance metrics. The results are validated using simulation. Apart from that our multi-priority architecture, validated in marginal cases, is compared to some existing single and two class priority models of multistage networks. This comparison is made by gathering metrics and comparing the total packet throughput. Also, the gain of the high-priority packets against the lower-priority packets under different configuration schemas is demonstrated. Eventually, this proposed analytical model is very accurate for various network sizes, with various values of offered multi-priority traffic on fabric's inputs and, therefore, can be used in performance prediction of multistage networks which supports quality of service. © 2011 Taylor & Francis.


Rizos G.E.,University of Peloponnese | Vasiliadis D.C.,University of Peloponnese | Stergiou E.,ATEI of Epirus | Glavas E.,ATEI of Epirus | Margariti S.V.,ATEI of Epirus
International Conference on Communications and Information Technology - Proceedings | Year: 2010

In this paper, we present a comparative study in a MANET environment. MANET is specifically characterized by high mobility of network nodes and frequent changes of direct visibility. We study the characteristics and performance of routing protocols that support multiple transmissions in ad hoc wireless networks, under different network loads, number of nodes within the network and mobility parameters. We present a model that incorporates nodes with role of proxy. The model is evaluated through simulation experiments in order to confirm the feasibility of his application in real conditions. In our measurements we use one proxy node in order to broadcast the messages in the destination. We use the file transfer protocol to measure the performance of our model. The protocol provides file downloading from a dynamically discovered service component available in a MANET locality, even if the server moves during file transfer.


Garofalakis J.,University of Patras | Stergiou E.,ATEI of Epirus
Journal of Communications | Year: 2010

Multistage Interconnection Networks (MINs) are used to interconnect different processing modules in various parallel systems or on high bandwidth networks. In this paper an integrated performance methodology is presented. A new approximate performance model for self-routing MINs consisting of symmetrical switches which are subject to a backpressure blocking mechanism is analyzed. Based on this, the steady-state distribution of the queue utilization is estimated and then all important performance metrics are calculated. Moreover, a general evaluation factor which helps in choosing a better performance MIN in comparison with other similar MIN architecture specifications is defined. The model was exemplified for the case of symmetrical single- and double-buffered MINs. It provides accurate results and converges very quickly. The obtained results were validated by extensive simulations and were compared to existing related work in the literature. © 2010 ACADEMY PUBLISHER.


Meletiou G.C.,A.T.E.I. of Epirus | Stamatiou Y.C.,University of Ioannina | Stamatiou Y.C.,University of Patras | Tsiakalos A.,University of Ioannina
Communications in Computer and Information Science | Year: 2011

In this paper we derive lower bounds for the degree of polynomials that approximate the square root of the discrete logarithm for Elliptic Curves with orders of various specific types. These bounds can serve as evidence for the difficulty in the computation of the square root of discrete logarithms for such elliptic curves, with properly chosen parameters that result in the curve having order of any of types studied in this paper. The techniques are potentially applicable to elliptic curves of order of any specific, allowable (by Hasse's bounds), order type that is of interest for the application in hand. © 2011 Springer-Verlag.


Rizos G.E.,ATEI of Epirus | Vasiliadis D.C.,ATEI of Epirus | Stergiou E.,ATEI of Epirus
Recent Researches in Communications and IT - Proc. of the 15th WSEAS Int. Conf. on Communications, Part of the 15th WSEAS CSCC Multiconference, Proc. of the 5th Int. Conf. on CIT'11 | Year: 2011

In this paper, we present a model that incorporates nodes with role of proxy in a MANET environment. MANET is specifically characterized by high mobility of network nodes and frequent changes of direct visibility. In partially connected ad hoc networks, the destination is not always reachable. In our model we need a proxy node to relay messages to the destination. Proxies are nodes that have high probability of reaching the destination. In our scheme, when a source sends a request for a destination and the destination is not reachable, then some of the nodes in the network will choose to become the proxy for the destination. The model has been evaluated via simulation in order to confirm the feasibility of his application in real conditions. In our measurements we use one proxy node in order to broadcast the messages in the destination.


Garofalakis J.,University of Patras | Garofalakis J.,Research Academic Computer Technology Institute | Stergiou E.,ATEI of Epirus
Future Generation Computer Systems | Year: 2013

The aim of this paper is to develop an analytical method for performance evaluation of double prioritized Multistage Interconnected Networks (MINs) with single or multilayers and backpressure operation which provide service differentiation and QoS guarantee to an end application running over next generation Internet or Grid systems. Specifically, a new architecture of switching elements is used for the construction of MINs. This switch element uses two parallel queues in order to serve dual priority traffic. Besides this, uniform traffic conditions are presupposed and the bulk of packet arrivals in each cycle to the network inputs follow a Bernoulli distribution. A new analytical model for evaluating single buffered MIN's with 2×2 special switching elements supporting internally two classes' priority traffic is presented. Equations for the steady state are derived. These equations are then used in finding the most important multistage network performance metrics, such as throughput, and packet latency. The results are also validated using simulation and compared with previous related work in marginal cases. This proposed analytical model is accurate for various network sizes and various values of offered traffic to the multistage network inputs. © 2012 Published by Elsevier B.V. All rights reserved.


Garofalakis J.,University of Patras | Garofalakis J.,Research Academic Computer Technology Institute | Stergiou E.,ATEI of Epirus
International Journal of Communication Systems | Year: 2011

Here a novel analytical method for performance prediction estimation of single- and multi-layer multistage interconnection networks (MINs) under multicast environments is presented. The 'Cell Replication While Routing' is used as a packet routing technique and the 'full multicast' mode as transmission policy is employed in all the MINs under study. This model is developed for single-layer MINs and is extended and applied to special types of multi-layer MINs, called semi-layer MINs, which support mixed traffic patterns such as unicast and multicast in uniform traffic conditions. The results confirm the significant performance saturation of single-layer MINs and the improvement of corresponding performance indicators by semi-layer MINs. The proposed analytical framework is anticipated to be a very useful tool in evaluating the performance of semi-layer MINs in designing more efficient QoS networks. © 2010 John Wiley & Sons, Ltd. Here a novel analytical method for performance prediction estimation of single- and multi-layer multistage interconnection networks [MINs] under multicast environments is presented. This model is developed for single-layer MINs and is extended and applied to special types of multi-layer MINs, called semi-layer MINs, which support mixed traffic patterns such as unicast and multicast in uniform traffic conditions. The results confirm the significant performance saturation of single-layer MINs and the improvement of corresponding performance indicators by semi-layer MINs. © 2010 John Wiley & Sons, Ltd. © 2010 John Wiley & Sons, Ltd.


Garofalakis J.,University of Patras | Garofalakis J.,Research Academic Computer Technology Institute | Stergiou E.,ATEI of Epirus
Performance Evaluation | Year: 2010

Nowadays, since the proportion of multicast traffic has increased compared to that of unicast traffic, the need for Multilayer Multistage Interconnection Layers Networks (MLNINs) has become more intense. In this paper a thorough evaluation of the performance of MLMINs using an analytical model is presented, as such an evaluation has not previously been developed. The multicasting policy that is used by MLMIN queues is the "partial multicast" and all the MLMINs studied use the "Cell Replication While Routing" (CRWR) technique. The performance model was applied under different offered loads to various network size MLMINs supporting various proportions of unicast and multicast traffic. The results have been confirmed in some marginal cases by existing work and the study reveals quantitatively the improvement in the performance metrics of MLMINs compared to the corresponding single-layer MINs. The findings of this paper are important as they could be useful in building optimum networks regarding their performance. © 2010 Elsevier B.V.


Garofalakis J.,University of Patras | Stergiou E.,ATEI of Epirus
International Journal of Network Management | Year: 2011

Multilayer multistage interconnection networks (MLMINs) integrate communication with network components and the components of parallel systems, especially when they service multicast traffic. This paper presents an approximate performance methodology for self-routing MLMINs that consist of two segments, each of which is composed of symmetrical switch elements. The first segment is subject to blocking situations with one mode of packet transmission policy (unicast). The second segment-the multilayer-is blocking free and employs double modes of transmission policy (unicast and multicast replication). Applying the current analytical model, which is based on a convergence method on the above types of MLMINs, an estimate can be made of their performance indicators. This model was applied to variable network size MLMINs under different multicasting patterns of traffic. It was also validated by extensive simulations. All the MLMINs under study apply special packet (traffic) management techniques, which allow for the integration of sub-networking into larger networks such as grids. The results are accurate and useful for network engineering, especially in the service of local area networks. © 2010 John Wiley & Sons, Ltd.


Stergiou E.,ATEI of Epirus | Margariti S.V.,ATEI of Epirus
AICT 2011 - 7th Advanced International Conference on Telecommunications | Year: 2011

The rapid deployment of networks in various environments demands accurate, efficient measurement in order to estimate path links. In this work, we considered the challenges posed by broadband networks for available bandwidth capacity evaluation. We focused on rate, using token bucket in cable modem end link with non-FIFO scheduling, and on burstiness type of traffic applied by multirate end-links in wireless network that follows the IEEE 802.11 protocol. We used a software tool for estimating the path rate capacity and we found that raw links and the corresponding token bucket rates were calculated in a quick and accurate manner. The accurate prediction of the available bandwidth in an end-point network link can help to avoid traffic bottlenecks, server choice, and overlay networks. Copyright © IARIA, 2011.

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