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Congestion control for the available bit rate (abr) service in asychronous transfer mode (atm) networks

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2005
Özzaman, Hülya Bozkurt
Congestion control is concerned with allocating the resources in a network such that the network can operate at an acceptable performance level when the demand exceeds or is near the capacity of the network resources. These resources include bandwidths of links, buffer space (memory) and processing capacity at intermediate nodes. Although resource allocation is necessary even at low load, the problem becomes more important as the load increases. Without proper congestion control mechanisms, the throughput may be reduced considerably under heavy load. Future applications are expected to require increasingly higher bandwidth and generate a heterogeneous mix of network traffic. ATM network is potentially capable of supporting all classes of traffic (e.g., voice, video, and data) and have multiple service classes allow audio, video and data to share the same network. Of these, the Available Bit Rate (ABR) service class is designed to efficiently support data traffic. Switch algorithms have been the most investigated topic of ABR. This has happened because the specification of ABR given by the ATM Forum allows a diversity of switch algorithms to be implemented. These range from the simplest binary switches to the more complex ER switches. The major part of this thesis has been devoted to ABR. First an introduction to the concept of congestion control and a brief literature survey of congestion control for ABR service of ATM networks are presented. Then two proposed congestion control mechanisms for the ABR service class in ATM networks are examined by means of simulation, showing the different degree of performance and complexity. The simulation results presented in this thesis were obtained using a network simulator written in C++. This network simulator is a small event driven program. Analytical results were derived for different network configurations and different