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Test Network (test + network)
Selected AbstractsQoS experiences in native IPv6 networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 2 2009Athanassios Liakopoulos Deployment of IPv6 technology in research and commercial networks has accelerated in the last few years. Inevitably, as more advanced services take advantage of the new technology, IPv6 traffic gradually increases. Today, there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks that support the Differentiated Services framework. As available software and hardware are designed to handle IPv4 packets, there is a need to accurately measure and validate performance of QoS mechanisms in an IPv6 environment. This paper discusses tests and technical challenges in the deployment of IPv6 QoS in core networks, namely the production dual stack gigabit-speed Greek Research and Education Network (GRNET) and the IPv6-only 6NET European test network, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common to IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class, while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state-of-the-art router cards at gigabit speeds. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the Internet routing protocol Enhanced Interior Gateway Routing Protocol: is it optimal?INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 3 2006James R. Yee Abstract Cisco's proprietary routing protocol, EIGRP (Enhanced Interior Gateway Routing Protocol) is one of the two most widely employed routing protocols in the Internet. The underlying algorithm is reputed to be optimal with respect to the EIGRP metric. We construct a counterexample to illustrate that it is not optimal. We implemented the test network from the counterexample in our Networking Lab and it was confirmed that the Cisco routers did not find optimal routes. We suggest ways in which the EIGRP algorithm can be improved. These suggestions would also improve the operation of the Diffusing Updating Algorithm, the portion of EIGRP used to recover from link/node failures. [source] Partition-based algorithm for estimating transportation network reliability with dependent link failuresJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2008Agachai Sumalee Evaluating the reliability of a transportation network often involves an intensive simulation exercise to randomly generate and evaluate different possible network states. This paper proposes an algorithm to approximate the network reliability which minimizes the use of such simulation procedure. The algorithm will dissect and classify the network states into reliable, unreliable, and un-determined partitions. By postulating the monotone property of the reliability function, each reliable and/or unreliable state can be used to determine a number of other reliable and/or unreliable states without evaluating all of them with an equilibrium assignment procedure. The paper also proposes the cause-based failure framework for representing dependent link degradation probabilities. The algorithm and framework proposed are tested with a medium size test network to illustrate the performance of the algorithm. [source] A dynamic shortest path algorithm using multi-step ahead link travel time predictionJOURNAL OF ADVANCED TRANSPORTATION, Issue 1 2005Young-Ihn Lee Abstract In this paper, a multi-step ahead prediction algorithm of link travel speeds has been developed using a Kalman filtering technique in order to calculate a dynamic shortest path. The one-step and the multi-step ahead link travel time prediction models for the calculation of the dynamic shortest path have been applied to the directed test network that is composed of 16 nodes: 3 entrance nodes, 2 exit nodes and 11 internal nodes. Time-varying traffic conditions such as flows and travel time data for the test network have been generated using the CORSIM model. The results show that the multi-step ahead algorithm is compared more favorably for searching the dynamic shortest time path than the other algorithm. [source] Robust Transportation Network Design Under Demand UncertaintyCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2007Satish V. Ukkusuri The origin,destination trip matrices are taken as random variables with known probability distributions. Instead of finding optimal network design solutions for a given future scenario, we are concerned with solutions that are in some sense "good" for a variety of demand realizations. We introduce a definition of robustness accounting for the planner's required degree of robustness. We propose a formulation of the robust network design problem (RNDP) and develop a methodology based on genetic algorithm (GA) to solve the RNDP. The proposed model generates globally near-optimal network design solutions, f, based on the planner's input for robustness. The study makes two important contributions to the network design literature. First, robust network design solutions are significantly different from the deterministic NDPs and not accounting for them could potentially underestimate the network-wide impacts. Second, systematic evaluation of the performance of the model and solution algorithm is conducted on different test networks and budget levels to explore the efficacy of this approach. The results highlight the importance of accounting for robustness in transportation planning and the proposed approach is capable of producing high-quality solutions. [source] Optimal transformations of asymmetric elements in three-phase networksEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2005Zdzislaw W. Trzaska Abstract This paper presents a procedure for optimal transformation of asymmetric three-phase elements. The proposed algorithm is based on the solution of the corresponding Steiner problem and improves the network voltage and current profiles. After identifying the phase quantities, the problem is formulated as a non-linear programming problem of the minimization of the sum of the r.m.s. values of the phase voltages and line currents under some constraint equations. A few test networks are used to verify the effectiveness and accuracy of the method. It is believed that practical applications of the proposed method will enhance the estimation of the phase asymmetry of the three-phase generator voltages and load currents. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||