Method of admission control and routing of virtual circuits

A method for operating a network of the kind that comprises a set of nodes connected by a set of links, and that in operation can be characterized by a network state, and wherein there are resources associated with each of said nodes and links, the method comprising, after a set of virtual circuits has been previously routed through the network, the steps of:

• receiving a request to route a virtual circuit on a path through the network between an origination node and a destination node;
• determining the load that fulfillment of the request would place on each link in a subset of the link set;
• and
• determining a respective cost for routing the request over possible paths between the origination and destination nodes, wherein:
• the possible paths comprise links in the link subset;
• the cost is a function of the network state;
• for each possible path, the cost includes a component for each link of said path, wherein each said cost component is a nonlinear function of the network state and of a parameter related to the number of hops for a subset of the previously-routed virtual-circuit set;
• and
• the method further comprises:
• selecting as potential paths in a set of potential routing paths, those possible paths having respective costs below a threshold, and
• selecting as routing paths in a set of routing paths those potential routing paths comprising nodes and links having sufficient associated resources for routing said request,
• selecting a path from said set of routing paths according to a criterion, and
• routing said request on the selected path.

A method of routing a request for a virtual circuit through a network, comprising:

• at an origination node, selecting a path from a set of routing paths, wherein:
• the selected path comprises nodes and links, the path-selection is carried out in response to a virtual-circuit request, and the path-selection is responsive to incomplete state information;
• attempting to route the virtual circuit on at least a portion of the selected path;
• while attempting to route the virtual circuit, collecting local state information from a node or nodes on at least one said portion, thereby to evaluate resources available at least at some nodes and links of the selected path;
• and
• if sufficient resources are found to be available, completing the routing of the virtual circuit on the selected path.