Patterns of Internet use have been evolving rapidly in recent years, shifting from delay- and bandwidth-tolerant applications like Web browsing, electronic mail, and file transfer toward more delay- and loss-sensitive applications like audio and video streaming or broadcasts [1], as well as real-time services such as Internet telephony or videoconferencing [2, 3]. At the same time, people are increasingly expecting these services to be available anywhere, anytime, and through any access technology. These developments are the onset of a converged Internet, embracing wireless home and enterprize networks, hotspots in coffee shops and airport lounges, as well as wide-area cellular networks.

The new heterogeneity in access technologies and the increasing mobility of Internet users calls for an efficient mechanism to handle active communication sessions among different points of attachment to the Internet. Users may change their point of attachment during movements, for better service quality through a different access technology or provider, to save access costs, or for fail-over or load balancing. The base Internet Protocol (IP) does not provide such flexibility. It was mainly designed for stationary nodes with fixed IP addresses. Much effort has hence gone into mechanisms that transfer an active communication session from one IP address to another when a mobile node changes its point of attachment to the Internet. Figure 14.1 illustrates such a redirection ...

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