ormance problems such as bottlenecks. 2.9 Summary The purpose of this chapter was to introduce the main aspects of OSS that will be covered in later chapters. An overview was given of each of the following topics: telecom network operations and maintenance traffic management OSS for Telecom Networks management of transport network infrastructure telecom network configuration management fault management for telecom networks telecom network security support for telecom network planning. ATM Network Management - The ATM Forum Model 3.1 Introduction to Asynchronous Transfer Mode (ATM) Asynchronous transfer mode (ATM) is a cell-based transmission or transport tech- nology. Cell-based means that information is carried in packages (or "cells") of some particular size. Transmission or transport is the carrying of information through a telecom network from a sender to a receiver. ATM works by setting up a connection between the endpoints for the duration of a communication session. It emerged with the aim of becoming the basic infrastructure for all broadband communications. ATM integrates essential features, such as QoS and traffic loss prioritisation. ATM scales to very large telecom networks without a loss in quality. The scalability of ATM along with its widespread implementation has made it a "future-proof" option for telecom network infrastructure. ATM is still the technology in most widespread use around the world for the core of telecommunications transport infrastructures.2 Nonetheless, network manage- ment remains a major challenge faced by ATM technology. ATM networks require more management procedures than pre-ATM networks. For example, ATM manage- ment does not concentrate only on the physical level, that is, monitoring the traffic through a wire or the status of a switch port, with a view to dealing with defects, fail- ures and malfunctions in wires, switches and other hardware. In fact, ATM focuses mainly on the logical level, with the overall goal of offering the preferred QoS and traffic control mechanism