A distributed channel-sense non-preemptive static priority ring for local area computer networks and its performance

Abstract

CHAPTER 1. INTRODUCTION 1 CHAPTER 2. OVERVIEW OF LANs AND THEIR MAC PROTOCOLS 6 CHAPTER 3. THE DISTRIBUTED CHANNEL-SENSE PRIORITY RING (DCPR) 32 CHAPTER 4. ANALYTIC MODELING OF DCPR CHAPTER 5. SIMULATION MODELING OF DCPR 93 CHAPTER 6. THE IMPROVED DCPR PROTOCOL CHAPTER 7, PERFORMANCE COMPARISON WITH KNOWN MAC PROTOCOLS 154 CHAPTER 8. CONCLUSIONS 169 BIBLIOGRAPHY 174 ACKNOWLEDGMENTS 17 APPENDIX: PASCAL LISTING OF DCPR SIMULATION PROGRAM 180 CHAPTER 1. INTRODUCTION Computer Communication Networks More than three decades ago when computing systems were first Installed a few peripherals such as printers, card readers, terminals, etc., operated as 'slaves' connected close to a single mainframe (or host) computer. Since that time, we have seen a tremendous decrease in hardware costs coupled with increase in processing speeds and memory capacities. The capabilities of the present day ubiquitous microprocessor serves as a testimony to that. As a natural consequence of these developments three main things began to happen [1,2]. First, we had computing systems in which hundreds of these peripherals (especially terminals), now more intelligent, were Installed to access one (or more than one) mainframe. At the same time, for convenience, these terminals were geographically dispersed so it became apparent that a cost-effective way should be found to allow them to access the hosts. The telephone network, already reaching most homes, became t:he obvious choice. Secondly, when it became apparent that the host computer could no longer cope with the processing functions special-purpose computers called front-end processors and later more sophisticated communication processors were developed to off-load to the communication-handling tasks from the host computers. Thirdly, several very large, powerful and specialized computers geographically distributed in a wide area had been installed. The potential users were also geographically dispersed. These large computers were so expensive that to duplicate them would not be cost effective so It was necessary to have them Interconnected. This enabled users connected to any host access to any other host along with any specialized software and/or hardware resources. This was the very situation In the late 1960s which fueled the Initiation of ARPA (Advanced Research Projects Agency) network by the U.S. Department of Defense. These three somewhat parallel activities, among others, brought about the concept, development, and Implementation of data and computer communication networks, thousands of which are deployed worldwide. They range from small networks which provide communications among devices within a single building or small geographic area to long-haul or wide area networks (WANs) which extend over large geographical areas such as countries, and In some cases literally spanning the globe. 12 Station Transmission Medium Figure 2-4. Ring topology 13 node. These measures result In increased complexity in the nodes. Ring networks will be discussed further later in this chapter. Medium Access...