ORMA: a high-performance MAC protocol for fiber-optic LANs/MANs

摘要

Emerging B-ISDN applications are accelerating the demand for high-speed and high-performance fiber optic local and metropolitan area networks (LANs and MANs). Most of the networks proposed for such an environment are based on either a folded bus or dual unidirectional bus technology, primarily due to the unidirectional nature of the fiber optic medium, their cost effectiveness, and their ability to carry asynchronous transfer mode (ATM) cells. Consequently, the design of the medium access control (MAC) protocols is the most crucial aspect for these networks since the decisions made at this level will determine the capabilities and the hardware cost of the network. The author proposes a novel MAC-layer protocol, called Optical Reservation Multiple Access (ORMA), which is suitable for data traffic on fiber optic folded bus MANs and LANs. Its main feature is an efficient optical reservation technique to allow stations to reserve transmission slots, which is attractive for use in fiber optic networks. Unlike conventional protocols. Where reservation is mostly done using software, ORMA performs its reservation using simple and effective optical circuits. Complete descriptions of the ORMA protocol and the associated nodes are given. Then the performance of ORMA is investigated as a function of the throughput, mean packet delay, and fairness among stations using analytical and simulation results. Our protocol is shown to achieve high throughput and small transmission delays while preserving the fairness of the whole network. Moreover, it compares favorably with related state-of-the-art networks. Thus, the ORMA protocol lends itself well to future-generation high-speed MANs and LANs.