A REVIEW OF THE FOUR MAJOR SONET/SDH RINGS

摘要

With the ever increasing bandwidth being transported over fiber optic cables, both buried and suspended from poles, rings have token the forefront as the means of providing self healing transport networks. These rings have taken many names over the past several years. This paper is a review of the four major ring types that are currently deployed, under development, being defined, or are for further study. These ring types are the unidirectional path switched ring, four-fiber bidirectional line switched ring, two-fiber bidirectional line switched ring and the unidirectional line switched ring. Each of these ring types provide their own unique capabilities and associated administrative and maintenance problems.