A simulation study on congestion control for the ATM ABR service

In this thesis, we have performed a simulation study on congestion control for the asynchronous transfer mode (ATM) available bit rate (ABR) service. Even though ABR is primarily intended for applications that can not describe their characteristics appropriately, it can be used by a wider range of applications since it provides some minimal guarantees for bandwidth. For the simulations, the ABR mechanisms specified in The ATM Forum Specification, Version 4.0 have been implemented to a great extent. Relative marking, enhanced proportional rate control (EPRCA) and efficient rate allocation algorithms (ERAA) have been realized, and their performances at ATM, TCP and application layers have been examined based on robustness, efficiency, fairness, buffer requirements and response time. The beat-down problem and large buffer requirements for the relative marking scheme have been illustrated. EPRCA was shown to be sensitive to parameters and result in oscillations in allowed cell rate. Finally, ERAA was shown to work efficiently with small buffers.