Efficient buffer management and scheduling algorithms for various QoS and traffic environment

Abstract

In this dissertation, we propose an efficient buffer management with priority, a scheduling algorithm guaranteeing the statistical QoS, and a multi-class scheduler supporting heterogeneous service classes. First, we propose an ATM multiplexer with a resume level control. The selective cell discarding scheme can be used to meet the different loss requirements of QoS by selectively discarding low priority cells form arrival traffic during periods of congestion. Control procedures depend on identifying the threshold or resume level of selectively discarding specific classes of cells. In ATM networks, priority control is explicitly performed using a one-bit cell loss priority (CLP) field in an ATM header within one connection. For digitized voice and video traffic, the packet classification is based on the significancy of information and codec. We examine a selective cell discarding scheme with a resume level control for two priority classes, in which cells are selectively discarded from arrival traffic during periods of congestion. we approximate a superposition of several independent and homogeneous On-Off bursty sources into a Markov-modulated deterministic process (MMDP) model, and use the embedded Markov chain approach to derive the steady-state queue distribution. The performance analysis of an ATM multiplexer with a resume level control derived here includes as special cases one without priority and one with a threshold level. We compare a resume level control with a threshold level control in terms of cell loss probabilities, mean queue length, mean queuing delay, level crossing rate, and queue length distribution at the embedded points. From the numerical results, it is shown that by controlling a higher level and a lower resume level a resume level control, the level crossing rate and the queue length distribution can be greatly reduced to improve the system operation. Also, we suggest the method to determine an appropriate higher and lower levels in a r...