Optimal PNNI complex node representations for restrictive costs

The Private Network-to-Network Interface (PNNI) is a scalable hierarchical protocol that allows ATM switches to be aggregated into clusters called peer groups. To provide good accuracy in choosing optimal paths in a PNNI network, the PNNI standard provides a way to represent a peer group with a structure called the complex node representation. It allows the cost of traversing the peer group between any ingress and egress to be advertised in a compact form. Complex node representations using a small number of links result in a correspondingly short path computation time and therefore in good performance. It is, accordingly, desirable that the complex node representation contains as few links as possible. In earlier work, a method was presented for constructing the set of the optimal complex node representations in the restrictive and symmetric cost case, under the assumption of a restricted set of optimal paths and a corresponding minimal path computation time. Here this method is extended to constructing the set of the optimal complex node representations appropriate for deployment in a heterogeneous environment where no uniform policy is used to derive them. These representations are not confined by a reduced optimal path constraint, and consequently use the absolute minimum possible number of links, resulting in a minimum path computation time.