A Hybrid Spanning Tree algorithm for efficient topology distribution in PNNI

Abstract

The ATM Forum's PNNI standard specifies a flooding mechanism to distribute topological state information amongst nodes participating in a PNNI network. While the flooding mechanism provides robust topology distribution, we show by simulation that it can disproportionately overload lower-bandwidth links and, due to its inherent redundancy, can generate considerable computational overhead due to the processing of redundant topology updates. To address these issues, we introduce the Hybrid Spanning Tree algorithm, a spanning tree-based topology distribution mechanism that has low computational maintenance and can support policy that restricts topology distribution control traffic from being carried over lower-bandwidth links. Unlike other spanning tree proposals, the Hybrid Spanning Tree algorithm provides a simple and practical migration path to smoothly transition PNNI nodes executing the flooding algorithm to those of the Hybrid Spanning Tree algorithm.