Research On Connection Admission Control Schemes In ATM Networks

The success of the future B-ISDN depends heavily on the ability to perform multiplexing of various services, such as voice, video, data, and so on. Different service has its own traffic characteristics and differentiated Quality of Service(QoS) requirement. So it is necessary to study traffic control mechanisms enabling the network to meet various QoS constraints defined for different services while achieving high resource utilization, in which Connection Admission Control(CAC) plays an important role. Currently, both ITU-T and ATM Forum only give simple definition for the function of CAC, and do not describe and standardize its behavior and scheme, so how to establish the real-time, high efficient and practical CAC schemes has been studied extensively in recent years. On the other hand, ATM is connection-oriented, the implementation of CAC function for SVC depends on ATM signaling system. However, as a result of having no necessary functions of call and connection control, the protocol stacks for ATM signaling defined by ITU-T can not realize the function of CAC and can not be used directly in the ATM equipment.In view of these reasons, combining with the National Defense Pre-research Project( 1996-2000) 揟he Research on User Access Equipment used in the Regional Transportable Communication Networks?and the National 863 project 揟he Practical ATM Switch used in the Access Networks? four issues are studied in depth in this dissertation, including queueing analysis and CAC schemes for CBR traffic in ATM networks, model-based CAC schemes for VBR traffic, estimation of QoS parameters based on measurement and measurement-based CAC schemes for VBR traffic, the key techniques of ATM signaling system.This dissertation consists of the following six chapters.Chapter 1 introduces the basic concepts of CAC and its importance. CAC schemes are classified based on such an idea that CAC should be structured differently for each service category. It explains the present status and problems in CAC schemes and ATM signaling system, and hence makes the research background clear. Finally, it presents detailed research contents carried and main contributions.Chapter 2 studies the CAC schemes for CBR traffic in ATM networks. The queueing problems of CBR traffic in ATM networks are analyzed. Simple closed expressions of the upper bound on the Cell Loss Ratio (CLR) and mean cell delay in a finite buffer system are derived. Consequently a new CAC scheme for CBR traffic,lv~眫{~L~: ATM~iija~jliJf~linear approximation CAC scheme based on the lowest rate replacing, is presented. Instead of using the tail of the infinite queue length distribution as an estimate to CLR, this CAC scheme obtains CLR by the upper bound on it, and QoS can be well guaranteed in our scheme.Chapter 3 studies the model-based CAC schemes for VBR traffic in ATM networks. A CAC scheme for VBR traffic based on the rate-modified model is presented. In this scheme, the source model is obtained from the source traffic descriptor (PCR, SCR, MBS) declared by the users at connection setup time and the direct effect of the relative values of the burst length and the buffer space on the cell loss performance is taken into account, which make our scheme be consistent with the standards and improve the resource utilization.Chapter 4 studies the measurement-based CAC schemes for VBR traffic in ATM networks. Making use of asymptotic analysis of a queue handling many traffic sources, a method for estimating QoS parameters based on measurement is presented, which takes into account the effects of the finite buffer space on the multiplexing performance. Consequently, a measurement-based CAC scheme is presented. It does not require any models describing the statistic of the traffic. Instead, in our scheme, network monitors and measures the incoming traffic statistics, and makes decisions to admit or reject based on the measured statistics, which enable it to overcome the drawbacks of the model-based CAC schemes.