Abstract: Scheme for the computation of a restrictive cost between pairs of border nodes of a PNNI peer group. A list of said links sorted according to their restrictive cost C is maintained. Logical sets of nodes are formed by taking one link after the other from said list starting with the cheapest cost C and assigning an identifier to the two nodes connected by the respective link, whereby the nodes of a set of nodes carry a dominant unique identifier if a border node is a member of the respective set, or a unique identifier if there is no border node being a member of the respective set. Sets are united if a link connects a node of a first set and a node of a second set, by assigning a dominant unique identifier to all nodes of both sets if either nodes of the first or the nodes of the second set carry a dominant unique identifier, or by assigning a unique identifier to all nodes of both sets if neither the nodes of the first nor the nodes of the second set carry a dominant unique identifier.