elements. Discussing all the different kinds of communication networks is outside the scope of this chapter. This chapter is intended to provide an overview on some of the popular communication networks that are used in telecom. The architecture, elements, and a brief description of element functionality is handled. The networks that are discussed briefly in this chapter are: ATM, UMTS, MPLS, GSM, GPRS, CDMA, IMS, and WiMAX. Based on the information presented in this chapter, the reader will be able to correlate components in any telecom network and hence have a basic understanding to manage the elements in the network as well as identify functionalities required in the management system. Independent of the network being handled, a management protocol needs to be used for data collection and information exchange between the network and management solution. This will ensure that the management solution interacting with elements in the network is nonproprietary and scalable. It should be noted that a telecommunication network can be a simple computer network, the Internet or a PSTN (public switched telephone network) and not restricted to the networks discussed in this chapter. 9.2 ATM Network The ATM (asynchronous transfer mode) is a packet switched network where data traffic is encoded into fixed size cells. It is connection oriented and requires a logical connection established between the two endpoints before actual data exchange. It can be used for both telecom and enterprise networks. An ATM network consists of the following main components (see Figure 9.1): Set of ATM switches: The core layer of the network usually has only ATM switches. ATM links or interfaces: Logical or physical link are used to connect components. ATM routers/hosts: The routers are used to connect to connect a switch with external networks and connections. They are also referred to as the ATM end system. There are two types of interfaces supported by an ATM switch: Network-node interfaces (NNI): This is the interface between two ATM swit