The Optical Transport Manager for PDH uses object classes to represent low-order SONET/SDH devices and populates them to the repository during discovery. The VMware Smart Assurance repository models the topology of the low-order SONET/SDH network being managed. This topology is used to build the codebook, which is the basis for root-cause analysis.
The PDH domain includes all of the low-order circuits with “SDH” link paths of VC11, VC12, and VC2. These are the lower-bandwidth devices with speeds of 1.5M, 2M and 6M respectively. High-order devices and protocols are populated to the SONET/SDH domain.
The Optical Transport Manager for PDH uses the relationships in the low-order SONET/SDH topology and cross-correlates with Optical Transport Manager for SONET/SDH domain to calculate the impact that a root-cause problem in one element has on the elements and services that are connected to, or depend on it.
Protection Schemes on page 95 provides more details.