1. A method executed in one or more processing modules for identifying a set of type-A nodes from a set of nodes m of a network having a working association with a set B of nodes b of said network, said nodes m are nodes that are not precluded from installing a processing module of said processing modules, hereinafter also referred to as potential type-A nodes, comprising the steps of: identifying a subset T of nodes b that are t-good, where a node m k is good for node b j if all lowest-cost paths from node b j to node m k leave node b j on one and the same link, and node b j is t-good if at least t of the potential type-A nodes are good for b j , where t is a preselected positive integer not greater than the number of said potential type-A nodes; then, choosing a subset of said potential type-A nodes as type-A nodes, such that that for each t-good node b in T, at least one node of the type-A nodes is good for node b; then, choosing zero or more additional ones of said potential type-A nodes as type-A nodes to cause a pair of two distinct type-A nodes m i and m j to exist for each t-good node b in T that is not also a type-A node, such that no node other than node b is on any lowest-cost path from b to m i and on any lowest-cost path from b to m j ; then, if there are nodes b in B that are not t-good, choosing zero or more additional ones of said potential type-A nodes as type-A nodes to provide, for each node b p in B that is not t-good, (a) one type-A node if said node b p in B that is not t-good is also a potential type-A node, or (b) a pair of type-A nodes, m i and m j , such that no node other than said node b p is on any lowest-cost path from b p to m i and on any lowest-cost path from b p to m j .