The Study of Access Schemes for High Speed LANs and MANs Based on Slotted Unidirectional Bus Structure

• Main Authors: Chung-Fu Lu, 呂崇富
• Other Authors: Han-Tzung Chen
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/52499408100237503932

碩士 === 國立臺灣科技大學 === 工程技術研究所 === 81 === Cyclic Reservation Multiple Access (CRMA) 和 Enhanced Cyclic Reservation Multiple Access (ECRMA)是兩種可應用於高速區域及都會 網路的新存取方式，它們是建構於時槽式單方向匯流排架構，並且可應用 於折疊式(Folded)及雙匯流排(Dual-bus)結構上。本論文旨在研究CRMA與 ECRMA 的介質存取控制(Mediumn access control)協定，並評估兩者的效 能(Performance) 。我們評估網路的效能包括：端點對端點延遲 (end- to-end delay) 及流通量比值 (throughput rate)。 CRMA和ECRMA 此兩 種存取方式與DQDB具有一個相同的特性，即其可達到網路的完全流通量( full throughput) 且與網路的距離及速度無關。但是與DQDB[10]相較之 下，CRMA及ECRMA 擁有下列兩項明顯的優點： (一) CRMA及ECRMA 具有 相當好的流通量公平性，但DQDB先天上即具有流通量不公平的特性。 (二) 因為可以預約連續的時槽，且傳送封包也是利用連續的時槽，所以 CRMA及ECRMA 便不須要使用任何的分段標籤及簡化封包重組之工作，但 DQDB卻需要。 Cyclic Reservation Multiple Access (CRMA) and Enhance Cyclic Reservation Multiple Access (ECRMA) are new access schemes for high speed local and metropolitan area networks based on slotted unidirectional bus structure, both folded and dual-bus configurations. The mediumn access control protocol and performance of CRMA and ECRMA are investigated in this paper. Performance measures obtained include end-to-end delay and throughput rate. Like the DQDB, both CRMA and ECRMA access schemes achieve full throughput independent of network speed and distance. However, they have two significant advantages over DQDB. First, they provide throughput fairness even at high speeds and large distances, where DQDB exhibits dramatic unfairness. Secondly, by allowing reservation of multiple consecutive slots, they make segment labeling unnecessary, and facilitate packet reassembly.