Προσεγγιστικά αναλυτικά μοντέλα για τη μελέτη της απόδοσης πολυβάθμιων διασυνδεδεμένων δικτύων μεταγωγής

Abstract

This research work concerns the performance evaluation of multistage, interconnected switching networks. To assess the performance, approximated analytical models are developed and presented. In particular: 1. A novel integrated methodology for assessing the performance of simple, self-routing, multistage, interconnected networks (e.g. banyan networks), which are formed by symmetrical switch elements, is presented. The model that is created is based on the function and behaviour of a random simple multistage switch system in a memory level (queue). Based on analysis, which includes a repetitive algorithm that converges within a small number of iterations, the queue's’ utilisation is estimated. Subsequently, other performance indicators are determined. 2. A performance evaluation process for multistage interconnection networks, which has the ability to service traffic with two or more classes of priorities, is presented. Particularly, a new switch element which has parallel memories in each entry is proposed to ensure effective servicing of multi-priority traffic. This switch element has one memory for each supported class of priority, and is modelled by means of queues. Based on the analysis provided by this model, and in conjunction with the application of a repetitive algorithm which converges with few iterations, all performance indicators were precisely calculated. 3. In addition, a novel analytical approach was developed that provides a performance evaluation of multistage interconnection networks that have one or more levels which apply the packet transmission ‘full multicast’ method when these networks serve unicast and multicast traffic. A relevant study model for those networks was created. It appears that the interconnected networks which have a limited number of levels lend excellent support with effective unicast and multicast traffic. 4. The study provides a performance evaluation of multistage interconnection networks with one or more levels, and uses a technical transmission packet technique for multicast traffic, the ‘partial multicast’ operation. 5. Also is presented an analytical approach that estimates a performance evaluation of self-routing, multistage interconnection networks (which have a limited number of levels) that apply two different transmission packet techniques in each segment. By application of a similar procedure, all the performance indicators of multistage networks are identified. 6. To assist designers, a compound performance factor (CPF) is defined which expresses the overall performance evaluation of multistage interconnection network devices (taking into account all the individual performance factors, according to a specific set of criteria). It is noteworthy that all of the analytical methods provide detailed results for all intermediate stages. All of the results obtained by application of analytical methods are confirmed by simulations. The results garnered by analytical methods are also compared with the results from previous work. The comparison highlights the greater accuracy and speed that these analytical methods have over older research techniques. Examination of the relevant research literature makes it evident that there is an insufficient number of analytical studies which cover the performance evaluation issue relating to modern switched networks; for example, multi-layered networks. This gap in the field of research is completed by this work. These analytical approaches will be useful tools for designers and manufacturers of network systems in their efforts to provide better quality of service (QoS).