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ATMSIM: A Simulator for ATM Networks - anoop - 08-16-2017 [attachment=15195] 1.1 Simulation Simulation plays an important role in computer-aided analysis and design of any system. Simulation technique has often been used to model and design communication networks. Before we build a system, it is important to evaluate the performance of various designs. In case of complex systems, it is di cult to build an analytical model that is mathematically tractable. In such cases, simulation of the system is often the only technique for performance evaluation. The simulation of large, complex, high-speed networks presents unique problems, such as setting up networks of di erent topologies and evaluating their performance parameters[16]. These problems can be addressed using statistical simulation techniques, such as importance sampling, distributed computing techniques. Thus, simulation has been playing an increasingly important role in the modeling and design of communication networks. 1.1.1 Advantages and drawbacks of simulation The advantage of a simulator, having modeling constructs closely related to the components of communication networks, is that development time of a target network becomes considerably small. The major drawback of basic network simulators is that they are limited to modeling only network con gurations allowed by the package's standard building blocks. Thus, if a communication system has some speci c features which are di cult to model, they have to be approximated to preserve its behaviour. However, there are several simulators that allow existing modeling constructs to be modi ed or new constructs to be created, with increased modeling exibility. 1.1.2 Types of simulation techniques In this section we discuss about various simulation techniques available. Process emulation Every component of the target system, i.e., the computer network to be studied, is represented by a separate process. Each process executes code corresponding to the code of its component. An advantage of process emulation is that all components of the target system can be tested. However, in order to faithfully capture the dynamics of the target system, it is necessary to periodically synchronize all the processes. The overhead involved in this process synchronization becomes a serious disadvantage. Discrete-event simulation In discrete-event simulation, the target system is modeled by a set of variables and a set of events[11][17]. Associated with each event is a routine that can update the set of variables. A simulation of the target system corresponds to a succession of event occurrences of time, i.e., a sequence of the form (e1, t1), (e2, t2), . . . , (en, en), where (ei, ti) denotes the execution of event ei's routine at time ti. The simulator executes a loop, with one event occurrence simulated in each iteration. It maintains the following two variables : simulated time, indicating the time of the last event simulated; and event list, consisting of a set of (e, t) pairs, where e refers to an event and t refers to the time instant when e is scheduled. In each iteration, the simulator removes an (e, t) pair with the earliest time from the event list, updates the simulated time to t, and executes the routine corresponding to event e. The simulation of event e can schedule new events, i.e., add new (e0 , t0) pair(s) into the event list. ATMSIM: A Simulator for ATM Networks - sjawade8 - 08-16-2017 ATMSIM: A Simulator for ATM Networks The existing simulators cannot provide an environment for simulating various protocols related to the ATM networks. Setting up an ATM network, which involves fiber optic cable and switches, is costly. The performance analysis of the ATM networks for different kinds of resource reservation and congestion control schemes, is required to decide whether to implement a particular scheme in reality. Thus, the need to develop a simulator for ATM networks has been felt. Discrete-event simulation technique offers the greatest degree of flexibility in modeling a simulator for an ATM network. Due to this reason ATMSIM, the simulator for ATM networks, is developed using discrete-event simulation technique. ATMSIM allows the user to define a network configuration consisting of a physical network and specifications of the components of the network. ATMSIM provides both steady-state and instantaneous performance measures to facilitate the study of complex dynamics that arises in ATM networks. ATMSIM has been used as a testbed for emulating a virtual reality model for ATM networks and to study the above mentioned schemes. ATMSIM: A Simulator for ATM Networks - asaf - 08-16-2017 For More IEE project on Network Simulation, view.. http://seminarsprojects.net/Thread-iee-project-idea-based-on-network-simulation |