t/server (perhaps preceding it in many cases) came seemingly small differences in applications. For instance, in the early 1990s, users began to attach files to electronic mail messages. Large differences came next-organizations added Web browsers to the standard desktop configuration. Suddenly the network was bursting at the seams with media-rich information pulled down from the Internet. As network throughput steadily declined, companies set out to build their own, internally- oriented versions of the Web-intranets became the rage. In some enterprises, the term network management may be an oxymoron. Yet even as companies struggle to accommodate an overabundance of bits, the usage model is changing again. Early adopters are deploying MPEG-compressed playback and interactive video applications over their networks. This often introduces congestion to a LAN segment. When such dense traffic traverses WAN links, traffic jams are almost assured. Fortunately, most organizations, before launching new applications, adapt their LANs and WANs to cope with the load. Adapting the network for streaming media means migrating toward infrastructures (hopefully enterprise-wide) that match service quality to traffic requirements. Before we talk about how this is done, we should review the differences between connection- oriented and connectionless networks. Connection-Oriented vs. Connectionless Networks Phone calls and circuit-switched videoconferences establish a path between parties for the duration of an exchange. Until the communication concludes and the connection is dropped, no one else can use the circuit. A busy signal is returned to those who try. This type of arrangement is said to be connection-oriented. Connection- oriented networks work well for time-dependent transmissions-streaming media-that require a constant bit rate (CBR). Applications in this class not only require a CBR, they need a guarantee that they will receive it. The term used to describe this type of service is isochronous. Isochronous service provides