ON AN EFFICIENT TRAFFIC MANAGEMENT SCHEME FOR TCP OVER ATM: GFR SERVICES

Abstract

Guaranteed Frame Rate (GFR) is an improvement over Unspecified Bit Rate (UBR) of ATM service category. It intends to provide legacy applications, especially TCP/IP data applications, with minimum rate guarantees at the frame level. Research focuses on the design of ATM switches that may provide the specified guarantees. The basic methods for supporting rate guarantees are buffer management and scheduling, integrated into the GFR implementations. As the scheduling part has inflexible implementations, effort is concentrated on the design of the appropriate buffer management or traffic management mechanism. The existing methods of buffer management provide the GFR services with a good efficiency, but they are complex in nature and it is very difficult to implement those algorithms. This leads to complex design of the switches. This report initially explains the GFR service and various mechanisms for providing GFR services and discusses important conclusions derived from relevant published papers. It then presents the most significant proposed GFR mechanisms and then investigates the performance of TCP traffic over ATM networks using GFR service categories. In this thesis three buffer management mechanisms have been implemented namely: Early Packet Discard (EPD) mechanism, EPD with packet push out buffering mechanism and finally the proposed mechanism. Simulation shows that TCP performance over GFR is improved with the proposed mechanism in terms of efficiency and fairness, as compared to their EPD counterpart. Further enhancement has been made in the proposed mechanism to make it more efficient for higher priority TCP packets in terms of throughput. The software is written in C++ under windows environment.