Method for preconfiguring a network to withstand anticipated failures

A method for restoring traffic in a network in which the network includes plural distinct nodes interconnected by plural distinct spans, each span having working links and spare links, and having a span capacity, each node having a digital cross-connect switch for making and breaking connections between links in adjacent spans forming span paths through a node, the method comprising the steps of:

• (1) for each of at least two possible span failures, (a) finding a number of restoration routes that are available in case of the occurrence of each span failure, (b) determining the resources used by each restoration route, and (c) determining the amount of flow to be restored for each span failure;
• (2) finding, in a computer, the amount of flow f.sup.p to be restored along each restoration route that minimizes total unrestored flow for all possible span failures identified in step 1;
• and
• (3) forming connections at each digital crossconnect switch in the network along each restoration route before occurrence of one of the possible span failures identified in step 1 to permit the amount of flow f.sup.p determined in step 2 to be carried by each respective restoration route upon the occurrence of one of the possible span failures identified in step 1.