Page 67 - DCAP601_SIMULATION_AND_MODELING

Unit 4: Discrete System Simulation (I)

Notes

Notes Object Oriented Simulation will succeed as a precious resource to students and skillful
professionals and researchers alike, as it offers an extensive, however intelligible
introduction to the fundamental principles of object-oriented , design and execution of
simulation models.

Statement from a Company about Discrete-system Simulation

Our Discrete-system Simulator (DSS) is used by INTRACOM, the largest Greek telecom company.
We shall expand DSS (in connection with the DSP library) to allow for the specification, simulation
and performance testing of distributed protocols for almost any form of environment, including
networks that allow hierarchical description, very fast networks and heterogeneous networks
with mobile units. The visualisation facility of DSS will be enhanced so the user can see the
protocol execution in very large networks in a meaningful way through, e.g., a hierarchical
description and graph-drawing techniques. INTRACOM, and also INTRASOFT
(the largest Greek software company), are interested in the new DSS and DSP library for (1)
simulating and testing distributed banking applications, and (2) designing hardware for fast
networks (routers and switches).

During the first year of ALCOM - IT, we established strong interactions with the industrial link
INTRAKOM/INTRASOFT a major Telecom and Systems House conglomerate of Companies.
After analysing the users’ needs, we identified a large algorithmic area which is a subset of the
area of on-line algorithms, namely the area of Call Admission Control (CAC) algorithms. Our
group and, in general, the ALCOM team has had already shown significant research on the issue.
Since the problem of Admission Control is currently addressing ATM network technology, we
decided to explore the transfer of algorithmic engineering technology in that area by specializing
and focusing the ALCOM-IT produced DSS tool in the above direction. The new DSS tool aims to
provide:
1. An abstract, clean and semantically correct high level model of any ATM network and of
the on-line calls for connections.

2. A library of Call Admission Control algorithms in a form that allows them to him easily
used by non - experts or to be used and tested by algorithms and networks designers.
3. The capability for the user Industry to design new Call Control protocols and/or test such
designs.
The ATM technology is considered as the state of the art network technology that is expected to
play an important role in the future networks. The ATM networks are fast packet switching
networks achieving their speed by avoiding flow control and error checking at the intermediate
nodes in a transmission. ATM operates in a connected mode, but a connection can only be set up
and serviced if sufficient resources are available in order to preserve the quality of service to the
previous accepted connections. This function is controlled by the Call Admission Control
algorithms running in the ATM switches.
DSS provides an abstract model for the description of any ATM network which is independent
of details of the underlying technology. It simulates the basic functionality of an ATM network
which IS that in each time unit cells are produced from traffic generators or forwarded from the
switches to their destination.
Under the scope of DSS an ATM network topology consists of links, ATM switches, terminals
(workstation) and call/traffic generators (network applications). The critical characteristics of
the topology such as the size of the buffers of the ATM switch, the bandwidth of the links, the

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