were not built for multimedia and, in particular, for appli- cations that involve video communications, multimedia collaboration, and/or interactive-rich media. Curiously, it is through the use of sophisticated computer applications and devices that we have been able to determine what the human information-processing model comprises: There is a very strong tendency for us to rely on the visual information stream for rapid absorption and longer retention. More than 50% of a human's brain cells are devoted to processing visual information, and combined with the delights of sound, smell, and touch-despite our enormous dependence on the written word-we're very active in processing the cues from the physical world. By changing the cues, we can change the world. Digital-rich media, in every conceivable sort of format-including audio, animation, graphic, full- motion video, application, whiteboards, and communities-will increasingly depend on multimedia. Video and multimedia applications require substantial bandwidth, as well as minimal latencies and losses. The table on the following page is a snapshot of the per-user bandwidth requirements for various services. Chapter 10 Next-Generation Networks Application Bandwidth Requirement E-mail and Web (not optimum support) 56Kbps Web as an always-on utility, crude hosted 500Kbps applications, 15-second video e-mail Hosted applications, reasonable videophone 5Mbps Massive multiplayer/multimedia communities 10Mbps Scalable NTSC/PAL-quality video 100Mbps Digital high-definition video-on-demand 1Gbps (uncompressed) Innovation applications (3D environments, 10Gbps holography, and SO on) Digital video and digital audio also require minimal, predictable delays in packet transmission, which conventional shared-bandwidth, connectionless networks do not offer. (Chapter 3, "Establishing Communications Channels," discusses connec- tionless networks in detail.) They also require tight controls over losses, and again, connectionless networks do not account for this. As more people simulta