SIMULATION: Transactions of The Society for Modeling and Simulation International

Obaidat, Mohammad S.

doi: 10.1177/003754979706800112pmid: N/A

doi: 10.1177/003754979706800111pmid: N/A

Bolla, Raffaele; Dalal'Ah, Ahmad; Davoli, Franco; Marchese, Mario

doi: 10.1177/003754979706800110pmid: N/A

Two event-driven simulation tools aimed at testing access control and routing mechanisms in an Asynchronous Transfer Mode (ATM) environment are presented. The first one is dedicated to the behavioural description of an ATM Virtual Circuit (VC) switch. The purpose is to test resource allocation and Call Admission Control (CAC) strategies, so only the relevant events for this objective are considered and some important functions (e.g., the switching element) for a complete description of an ATM switch are not explicitly modeled. The second simulator has been designed to test routing strategies for an ATM network. In such a case, a higher level of abstraction than in the previous one is necessary and, again, only the meaningful events to the aim are taken into account. Some resource allocation, CAC, and routing schemes are also reported, along with the description of the simulation tools. Several simulation results are discussed, in order to assess their performance.

Arlitt, Martin F.; Williamson, Carey L.

doi: 10.1177/003754979706800109pmid: N/A

Given the continued growth of the World-Wide Web, performance of Web sewers is becoming increasingly important. File caching can be used to reduce the time that it takes a Web server to respond to client requests, by storing the most popular files in the main memory of the Web sewer, and by reducing the volume of data that must be transferred between secondary storage and the Web server. In this paper, we use trace-driven simulation to evaluate the effects of various replacement, threshold, and partitioning policies on the performance of a Web sewer. The workload traces for the simulations come from Web server access logs, from six different Internet Web sewers. The traces represent three different orders of magnitude in sewer activity and two different orders of magnitude in time duration. The results from our simulation study show that frequency-based caching strategies, using a variation of the Least Frequently Used (LFU) replacement policy, perform the best for the Web sewer workload traces considered. Thresholding policies and cache partitioning policies for Internet Web servers do not appear to be effective.

Szarkowicz, Krzysztof; Fodor, Gábor; Faragó, András; Henk, Tamás

doi: 10.1177/003754979706800108pmid: N/A

This paper begins with an overview of multicast algorithms, which are the most promising candidates to be in wide use in first generation Asynchronous Transfer Mode (ATM) based Broadband Integrated Services Digital Networks (B-ISDN). Since the Multiple Destination Routing (MDR) problem and the associated Steiner Tree problem are known to be NP-complete and therefore a number of heuristic algorithms have been proposed in the literature, we first need to establish which of these are the best candidates for the B-ISDN. We conclude that the weighted greedy -type algorithms are promising ones, and therefore we examine the behavior of these algorithms in terms of blocking probability and network utilization. In doing so, we use a B-ISDN call level simulation program, which proves to be an indispensable tool in the quest for efficient multicast algorithms. We find that shortest path routing with appropriate (adaptive) weight functions combined with the complete partitioning link allocation policy may give satisfactory blocking values and good network utilization in networks of different sizes.

Jia, Xiaohua; Pissinou, Niki; Makki, Kia

doi: 10.1177/003754979706800107pmid: N/A

Multicast has become an important service in modern network applications. Multicast routing is a difficult issue, particularly under delay or bandwidth constraints. This paper discusses Steiner trees in the modeling of multicast routings and various routing constraints required by applications. It also discusses the existing multicast routing algorithms, especially the routings under constraints, such as delay constraint, limited available bandwidth, and traffic load balancing. Extensive simulations have been conducted to reveal the relationships between the network cost of the routing and each of the discussed constraints.

Ast, László; Cinkler, Tibor; Fodor, Gábor; Rácz, Sándor; Blaabjerg, Søren

doi: 10.1177/003754979706800106pmid: N/A

For the end-to-end (Originator-Destination pair) call blocking probability computation in multirate loss networks the so-called reduced load approximation under link independence assumption is often used, because it allows the derivation of analytical and numerical results. Its accuracy and extendibility to multirouting or multicasting networks (like me B-ISDN), however, is seldom studied. This paper attempts to generalize this assumption and to assess the usefulness of this generalization by comparing simulation and approximation results on link, route, and end-to-end blocking probability evaluation for these kinds of networks. The accuracy of the approximation is examined by a simulation tool called Flexible Simulation Platform for ATM Networks. An important application example of this generalized link-, route- and Originator-Destination pair blocking measure is the formulation of an optimization model for multirate loss networks, which optimizes carried traffic and network revenue.

doi: 10.1177/003754979706800105pmid: N/A