Patent ID: 7280470
Filing Date: 2007-10-09
Classification: H04J

Abstract:
1. A network node for a bidirectional ring topology network having first and second working rings and first and second protection rings, wherein each of said working rings and each of said protection rings has an insertion point for inserting an add-up signal from an external source site into the ring and a termination point for extracting a signal from the ring onto an external sink site, said network node serving as one of said insertion and termination points, the network node comprising: a first demultiplexer for receiving a multiplex signal from one of said working rings for producing a first drop-off signal; a first multiplexer for multiplexing an add-up signal from the external source site onto said one working ring; a first protection switch connected to said external source site; a first path switch for exclusively establishing a connection between said first demultiplexer and said first multiplexer or between said first multiplexer and said first protection switch; a second demultiplexer for receiving a multiplex signal from one of said protection rings for producing a second drop-off signal; a second multiplexer for multiplexing the add-up signal from the external source site onto said one protection ring; a second protection switch connected to said external sink site; a second path switch for exclusively establishing a connection between said second demultiplexer and said second multiplexer or between said second multiplexer and said second protection switch; and control circuitry for monitoring said working rings and controlling said first and second protection switches, and controlling, if said network node serves as said insertion point, said first protection switch so that said add-up signal from the external source site is coupled via said first path switch to said first multiplexer when no failure is detected in said working rings and is coupled via said second path switch to said second multiplexer when a failure is detected in said working rings, and controlling, if said network node serves as said termination point, said second protection switch so that said first drop-off signal from said first demultiplexer is coupled to said external sink site when no failure is detected in said working rings and said second drop-off signal from the second demultiplexer is coupled to said external sink site, instead of the first drop-off signal, when a failure is detected in said working rings.