Patent ID: 8605576

Claim:
A communication network system comprising: a processor; a plurality of node apparatuses using a protocol to establish paths therebetween, and a plurality of intermediate node apparatuses provided on the two paths and configured to pass on a packet data including a user data, where each of the intermediate node apparatuses stores a line/path database including data on an identifier of a path connected to a downstream-side line, through which the packet data is transmitted from the intermediate node apparatus to an adjacent intermediate apparatus provided on a downstream side, wherein the processor transmits an UNUSED packet data indicating that the packet data is not transmitted to a path which is established but not currently used to transmit the user data, wherein the processor determines each of the node apparatuses to be a packet source or a packet destination, and operates to detect an occurrence of failure in two paths being established between the packet source and the packet destination in the communication network system, wherein the processor transmits packet data including user data through one of the two paths, and when one of the node apparatuses detects an occurrence of a failure in one of the two paths, the processor changes the path to the other path, wherein the processor detects an occurrence of a failure in an upstream-side line, through which the packet data is transmitted from an adjacent intermediate node apparatus to the intermediate node apparatus, wherein when the failure in the upstream-side line is detected, remote defect indication (RDI) packet data indicating an alarm is transmitted to the upstream-side adjacent intermediate node apparatus, and, upon receiving the RDI data transmitted from the downstream-side adjacent intermediate node apparatus, path-RDI (P-RDI) packet data indicating an alarm to each path, is transmitted to the path connected to the downstream-side line by referring to the line/path database, wherein when the processor receives the P-RDI data indicating the occurrence of the failure in the path, the processor changes the path to a different path, wherein, upon detecting the failure in the upstream-side line, the processor transmits path alarm indication signal (P-AIS) packet data indicating an alarm to each path to a node apparatus functioning as a destination of the packet data including the user data via the downstream-side intermediate node apparatus, wherein, upon receiving the P-AIS data transmitted through the path on which the UNUSED packet data is transmitted, the processor transmits to the path to be used a USED-N packet data that indicates reception of the P-AIS data transmitted through the path on which the UNUSED packet data is transmitted, and wherein, upon detecting the occurrence of the failure in the path by receiving the USED-N packet data through the path on which the UNUSED packet data is transmitted, the processor changes the path to a different path.