Apparatus and method for calculating communication paths

A system for calculating a plurality of end-to-end paths each Having a given bandwidth and communicably connecting two terminal nodes in a communication network divided into a plurality of areas, the system comprising:

• a first path calculating device to:
• select, from among the plurality of areas, a first sequence of passage areas to be traversed by a first end-to-end path and a second sequence of passage areas to be traversed by a second end-to-end path, and
• select, from among the first sequence of passage areas, multi-path passage areas each defined as an area to be traversed by two or more end-to-end paths;
• and
• a second path calculating device to calculate two or more intra-area paths for each of the multi-path passage areas, each of the two or more intra-area paths being defined as a communication path having the given bandwidth and communicably connecting two different boundary nodes with an area, the two or more intra-area paths being calculated by a node in the each of the multi-path passage areas based on a path calculation requesting message that is transferred along the first sequence of passage areas, the path calculation requesting message including bandwidth information indicating the given bandwidth, passage area information identifying the first sequence of passage areas, and multi-path passage area information identifying the multi-path passage areas, wherein
• the first path calculating device sends to the second path calculating device information on the first sequence of passage areas and the multi-path passage areas,
• the second path calculating device sends to the first path calculating device the result of calculating the two or more intra-area paths for each of the multi-path passage areas,
• the first path calculating device selects, for each of the multi-path passage areas, first and second intra-area paths from among the calculated two or more intra-area paths, and
• the first path calculating device determines the first and second end-to-end paths so that the first and second end-to-end paths include the selected first and second intra-area paths, respectively, and each of the first and second end-to-end paths has the given bandwidth.

A method for calculating a plurality of end-to-end paths each having a given bandwidth and communicably connecting two terminal nodes in a communication network divided into a plurality of areas, the method comprising:

• selecting, from among the plurality of areas, a first sequence of passage areas to be traversed by a first end-to-end path and a second sequence of passage areas to be traversed by a second end-to-end path;
• selecting, from among the first sequence of passage areas, multi-path passing areas each defined as an area to be traversed by two or more end-to-end paths;
• calculating two or more intra-area paths for each of the multi-path passage areas, each of the two or more intra-area paths being defined as a communication path having the given bandwidth and communicably connecting two different boundary nodes with an area, the two or more intra-area paths beings calculated by a node in the each of the multi-path passage areas based on a path calculation requesting message that is transferred along the first sequence of passage areas, the path calculation requesting message including bandwidth information indicating the given bandwidth, passage area information identifying the first sequence of passage areas, and multi-path passage area information identifying the multi-path passage areas;
• selecting, for each of the multi-path passage areas, first and second intra-area paths from among the calculated two or more intra-area paths, and
• determining the first and second end-to-end paths so that the first and second end-to-end paths include the selected first and second intra-area paths, respectively, and each of the first and second end-to-end paths has the given bandwidth.