Congestion Avoidance in IP Networks

Abstract

With the profilerence of multimedia traffic over the Internet, it seems natural to move over to ATM technology which has been designed specifically to support integration of data, voice, and video applications. While multimedia applications are still in the development stage, most of the traffic on the Internet today is data traffic in the sense that they are bursty and relatively delay insensitive. It is, therefore, natural to ask how the current applications will perform over the ATM technology. Although ATM technology ! as been designed to provide an end-to-end transport level service and so, strictly speaking, there is no need to have TCP or IP if the entire patl1 from source to destination is an ATM path. However, in the foreseeable future, this scenario is going to be rare. A more common scenario would be where only part of the path is ATM. In this case, TCP is needed to provide the end-to-end transport functions (like flow control, retransmission, ordered delivery) and ATM networks are used simply as "bit pipes". Since the Available Bit Rate (ABR) service class has been developed specifically to support data applications, it is important to investigate the performance of the dominant Internet protocol Transmit Control Protocol (TCP) over it. The thesis has three main contributions. First, it presents a novel technique for the design of an ATM switch supporting ABR flow control using fuzzy logic. The second contribution of the thesis is the design and implementation of an event-driven object-oriented network simulator, which can be used. to evaluate the performance of any given ATM network topology running TCP applications. Third, simulation results are performed to maximize the throughput ofTCP over ATM, as well as ensuring the best possible fairness among different competing user requirements.