الفهرس 
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Abstract
A computer network serves to share information between computers. Information can be data, voice or image. Asynchronous Transfer Mode (A TM) is thought to efficiently transfer all kinds of information. This thesis is aimed to study ATM switching systems. We will study the switching capabilities of the A TM switching systems and suggest some improvements. The thesis consists of five chapters, conclusion, appendices and references.
Chanter one
This chapter is an introduction to the thesis. We begin by surveying the evolution of different communication protocols. We explain why A TM is thought to be the future Broadband Integrated Service Digital Network (B-ISDN) solution. It is thought that with A TM there will be one network responsible for transporting all kinds of information. Finally a thesis overview is presented where we explain what is each chapter about.
ChaDter two
This chapter gives a general description of ATM. It first presents the A TM network structure and how a traditional A TM based network is laid out. The concept of Virtual Channels (VC) and Paths (VP) is also explained. The cell format is demonstrated. How the routing is done with ATM is explained in this chapter. We present the different ATM layers. we explain the
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signaling used to setup and clear A TM connections. The Private Network-to-Network
Interface (PNNI) is the interface bet\’,:een A TM switches. Later in this chapter, the network building topology and the address structure are explored.
ChaDter three
This chapter is dedicated to switching systems architectures. There are many considerations to be taken in the design of a switching system such as supported bit rates, throughput, delay and broadcast/multicast capabilities. We are looking for a switching system with high speed,
large number of ports and modular. A switching element is a basic switching building block to construct a switching fabric. Some examples of switching elements are given. Some switching fabrics can have internal cell loss probability and some do not.
Both types of switching fabrics are explained with examples. The theory of operation along with a general performance evaluation will be presented.
Chapter four
This chapter aims to study the Knockout based switching systems. The Knockout switching principle is to choose some number of winners out of the candidate cells for one or a group of outlets. We have implemented a computer program that calculates the throughput expressed in cell loss probability from an analytical solutiol).. presented by other researchers. The results are then presented to compare between different loading conditions and switch sizes. A simulation of the actual switching process of the Knockout switching system is then presented introducing losses that were not considered by other researchers.
Chapter five
This chapter is dedicated to study the Banyan networks, which are self routing switching systems with zero cell loss probability. We begin the chapter by giving a detailed description of the Banyan networks, explaining the principle of operation and performance under various traffic patterns. We review different means to improve the performance proposed by other researchers such as multibuffering and parallel networks. We then present our improvements on the Banyan network. We discuss the optimum buffer sizes and distribution through the network. We also present a new topology for the Banyan network and a new switching element. The new configuration will significantly improve the performance. Finally, we discuss the new modifications advantages and drawbacks.
Chapter six
This is a general discussion of the results of the research presented in chapter four and five. A general evaluation of the Knockout switching element and the generalized Knockout switching fabric is given. The research results on Banyan networks are also discussed later in this chapter. We focus in this chapter on the performance and the factors that alTect it. The keys to improve the performance are the main concern of the last chapter. We will also discuss why there are so many switching systems available and the basis of comparison among them.