الفهرس 
Integrated Services Digital Network ISDN
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Abstract
. ”Traffic Control in ATM Networks”. Ph.D.
Degree, Ain Shams University. Faculty of Engineering. Electronics and
Communication Engineering Department. 1999.
ATM is the transfer mode of choice of the B-ISDN. ATM is a packet-oriented
switching and multiplexing technique. High transmission rates are expected to
offer full bandwidth flexibility and high bandwidth utilization, and provide the
quality of services required by applications with a wide range of performance
requirements through statistical multiplexing. A™networks have multiple
service classes allowing voice, video, data, and text in an integrated manner to
share the same network. Of these, the Available Bit Rate (ABR) service class is
designed to efficiently support data traffic.
The general problem of network traffic involves all the available traffic
classes. In this thesis, we address the problem of designing traffic control
mechanisms for one class- the ABR service class in ATM networks.
Congestion control in ATM networks has been classified into two
categories preventive and reactive control. The former tries to prevent congestion
before it happens while the latter reacts to the congestion after it occurs and tries
to bring the degree of network congestion to an acceptable level.
Preventive control consists of Usage Parameter Control (UPC)and Connection
Admission Control (CAC). The role of the UPC is to police established
connections and ensure that the users traffic conforms with the requirements
agreed during connection establishment. The CAC is responsible for allocating
resources dependent on the type of traffic the user wishes to send over the
network, for each connection set-up. Accurate and simple characterization of the
different possible sources are therefore very important. This work began,
therefore, with an examination of the various traffic models that are available.
The most versatile of these models; the On-Off model has been used to represent
ATM sources. We then studied the known CAC algorithms both analytically and
by simulation from which we concluded that the bandwidth assignment is
.
strongly dependent on the particular traffic characteristics.
In this thesis, we investigate the use of preventive control mechanisms in
solving the problem of traffic control, (using leaky bucket policing mechanism).
Emphasis in this work is given to determine the parameters of the leal]’ bucket
and to optimize the mechanism, which is used to monitor and control the traffic
in terms of conformity with the agreed traffic contract at the user access. We also
examined the performance characteristics such as reaction time, cell loss