Synchronous Digital Hierarchy Optical Metropolitan Network Ring Traffic Analysis

As a result of the Synchronous Digital Hierarchy (SDH) standards, new network topologies are being introduced into existing networks. These new topologies include unidirectional and bidirectional rings in an environment which was previously dominated by point to point interconnections in meshed structures. Analysis of the traffic statistics of existing Plesiochronous Digital Hierarchy (PDH) metropolitan networks using various SDH network topologies is required in order to be able to determine optimal SDH network topologies. Existing bandwidth switching methodologies must be included in this analysis to determine the effects of these bandwidth routing methodologies. Several proposed hierarchical metropolitan optical transmission network architectures are examined in this paper in order to be able to determine strategies for the introduction of SDH capabilities into existing networks. An actual metropolitan network is used as a case study to evaluate traffic flow in several proposed hierarchical ring network topologies. These topologies include both unidirectional and bidirectional rings in three different hierarchical structures: a three level, a two level, and flat network hierarchies. The transmission requirements for these hierarchies with a central switching constraint are analyzed. The results indicate that existing centralized switching methodologies reduce the bandwidth carrying capacity advantage of bidirectional rings over unidirectional rings in hierarchical topologies.