What is Host-Multicast

This article discusses the use of policies to control calls—whether in traditional telephony or in its more modern versions such as mobile telephony or Internet telephony. Call control is as old as telephony. It allows subscribers and the network to manage calls. Trivially, users initiate calls by dialing and terminate calls by hanging up. However, modern telephony offers many more options for managing calls. For example, they may be forwarded if the user is busy or away. Conference calls may be set up. Voicemail and answering services can be used to take messages. The solutions in conventional telephony are, however, relatively limited. This article investigates the relevance to call control of the kinds of policies used to manage computerized and networked systems. As will be seen, policy-based management of call control offers a much more flexible approach.