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, therefore, desirable that the complex node representation contain 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, such as bandwidth, under the assumption of minimal path computation time. In the present paper, this method is extended for constructing the set of the optimal complex node representations which are not confined by a reduced path computation time constraint, and consequently use the absolute minimum possible number of links.