The present document provides an information model for the performance monitoring of Synchronous Digital Hierarchy (SDH) network. This model describes the managed object classes and their properties for the performance monitoring function@ as defined in ITU-T Recommendation G.784 and EN 301 167 and as related to SDH Network Elements (NEs). These objects are useful to describe information exchanged across interfaces defined in ITU-T Recommendation M.3010 Telecommunications Management Network (TMN) architecture for the management of the performance monitoring function. PDH performance monitoring functions are used to monitor specified performance events of specified termination points managed objects as defined in EN 300 371 and to report these performance data@ as well as quality of service alarms to its managing system according to a given schedule. ITU-T Recommendation M.2120 defines maintenance of transport network@ ITU-T Recommendation G.784 defines the management of SDH based NE. The present document defines the object model based on ITU-T Recommendation Q.822 according to the requirements described in ITU-T Recommendation G.784@ EN 301 167 and ITU-T Recommendation M.2120. This model uses generic mechanism defined in ITU-T Recommendation Q.822. The present document defines: - an information model@ as related to the performance monitoring function for the Plesynchronous Digital Hierarchy (PDH). The present document does not define: - the protocol stack to be used for message communication; - the network level management processes; - the application contexts; - the conformance requirements to be met by an implementation of this information model; - information models for other systems or equipment. The information model defined here (and the corresponding message set) is concerned with the management of NEs@ the equipment by which they are implemented and the functions contained within them. More precisely@ it applies to an equipment domain visible at the element manager to element interface and is only concerned with information available within that domain. Information proper to the domain of a network level management process is not included within this model.