Relaxed constrained shortest path first (R-CSPF)

An apparatus comprising:

• one or more network interfaces for communication with a computer network;
• a processor coupled to the network interfaces and configured to execute software processes;
• and
• a memory configured to store an indication of a target bandwidth for a constrained path from a source to one or more destinations in the computer network, a lower bandwidth boundary constraint for the constrained path that is less than the target bandwidth, and an upper cost boundary constraint for the constrained path, the memory further configured to store a path computation process executable by the processor, the path computation process when executed operable to
• compute a set of paths from the source to the one or more destinations that have bandwidth within the lower bandwidth boundary constraint and cost within the upper cost boundary constraint, and
• determine whether one or more paths of the set of paths has bandwidth that provides at least the target bandwidth and, if so, select a path from the one or more paths of the set of paths having bandwidth that provides at least the target bandwidth to use as the constrained path, and, if not, select a path from the one or more paths of the set having bandwidth that does not provide at least the target bandwidth that has bandwidth closest to the target bandwidth to use as the constrained path.

Software encoded on one or more non-transitory computer-readable media that when executed by a processor is operable to:

• maintain a target bandwidth for a constrained path from a source to one or more destinations in a computer network;
• maintain a lower bandwidth boundary constraint for the constrained path that is less than the target bandwidth;
• maintain an upper cost boundary constraint for the constrained path;
• compute a set of paths, by a node of the computer network, from the source to the one or more destinations that have bandwidth within the lower bandwidth boundary constraint and cost within the upper cost boundary constraint;
• and
• determine whether one or more paths of the set of paths has bandwidth that provides at least the target bandwidth and, if so, select a path from the one or more paths of the set of paths having bandwidth that provides at least the target bandwidth to use as the constrained path, and, if not, select a path from the one or more paths of the set having bandwidth that does not provide at least the target bandwidth that has bandwidth closest to the target bandwidth to use as the constrained path.