Patent ID: 6366556
Filing Date: 2002-04-02
Classification: H04J,Y10S

Abstract:
A method for restoring service in a path segment of a SONET communications network comprised of a plurality of nodes interconnected by a plurality of line segments using a virtual ring topology to establish a protection ring to bypass defective line segments and line terminating equipment that normally carry communications signals between a source node and a destination node of said path segment, and only when a defect is within said path segment and not external to said path segment, and wherein said network has a SONET path overhead that includes parity error compensation, said method comprising the steps of:determining the number of parity errors incoming to said source node of said path segment or detecting said SONET path defect; creating a message at said source node, said message being inserted into and carried in a previously unused byte of the SONET path overhead, said message being used to carry information from said source node to said destination node; writing said number of incoming parity errors into said message; computing the total number of parity errors arriving at said destination node; computing the number of parity errors introduced only in said path segment by subtracting the number of incoming parity errors written into said message from the total number of parity errors computed to be arriving at said destination node, said parity errors introduced in only said path segment being used to cause said protection ring switching only when said path segment is determined to be defective by exceeding said pre-determined number of parity errors in said path segment; and switching to said protection ring to carry said communications signals and bypass said path segment only when it is determined to be defective by exceeding a pre-determined number of parity errors in said path segment or by detecting a SONET path defect.