With the advent of high-speed networks, it is possible to build multimedia distributed applications that involve a geographically dispersed group of users. Development of such applications requires support for coordination and temporal synchronization of traffic over related streams. For instance, one must consider the problem of coordination in a multipoint communication where more than one sender may transmit data at the same time. Also, a multimedia application may need to synchronize traffic over multiple connections, each carrying traffic from a different medium. When a participant scrolls through an image browser (or a shared editor window) and says, "look at the middle of the display", the statement should be heard at the same time (or just after) the scrolling is completed. Such temporal relationships must be captured in the delivery of traffic over related flows. Existing transport and/or session layer protocols do not explicitly include communication abstractions t...