Susumu Nakayashiki

Wrapping and merging reconfiguration mechanism of a counter-rotating dual ring

A counter-rotating dual ring incorporates a reconfiguration capability that significantly increases the reliability of a ring local area network. Automatic wrapping and merging reconfiguration techniques without specific supervising station are presented. Stations are connected by two link pairs, each consisting of an incoming signal link and an autograph signal link. In normal operation two rings are formed. A primary ring is used for user data transmission, and a secondary is used for backup. When a failure occurs on the primary ring, either ring switch or wrapping takes place. Ring switch means that the secondary ring assumes the roll of the primary ring. Wrapping means that the signal from the input side of one link pair is turned around to the output side of the same link pair to avoid the failure. This automatic wrapping mechanism restores a closed ring and can be used with the case of MAC (media access control) layer failure as well as physical layer failure. The station continues to monitor the failed links; when the failure is remedied, the failed portion forms another wrapped ring. The two wrapped rings are then combined together (merging) after it is certified that they are both functioning properly. If another failure occurs on the wrapped ring, the same wrapping mechanism enables smaller wrapped rings to be formed.<<ETX>>