ps. The specification of an information model is mandatory before we can talk about vendor-independent network management. The information model is specified by the management information tree (MIT) or management information base (MIB), which defines all managed objects in a system. The managed objects contain all resources that the man- agement system can access. Each managed object has a unique identification that consists of a sequence of names (or numbers) starting from the root and having multiple options at each level. For example, at the second level after the root we have one branch for the ISO (1) and another for the ITU-T/CCITT (0) and an object identifier contains ISO if this is specified to be the right path to our system and its managed objects. The highest levels of the MIT are standardized, but the compatibility of the systems from dif- ferent vendors requires detailed standardization down to the managed object and its behavior. For example, if we want to get information about whether subscriber 1 of an exchange is busy, we must have a complete specification of what kind of message, transmitted to the exchange, will produce the wanted response regardless of the manufacturer of that exchange. The lower-level protocols define the structure of the messages, and the information model must specify in detail the information content of the management message with which the The Telecommunications Network: An Overview network element responds. For example, all exchanges should respond with exactly the same message if subscriber 1 is busy. Much work remains to standardize the network management functions of the present systems in the public telecommunications network and new systems require their own standards for network management. However, the Internet community has achieved detailed MIB specifications for many LAN and Internet systems. This has made many NMS software tools, which can manage multivendor local networks, available for LAN environments. In this chapter we have looked at telecommunications ne