IS managers see another picture. You observe the Internet straining to display raggedy streaming video in small screen windows-a far cry from the "business quality" sound and pictures your bosses will expect over your intranet. You have a justifiable fear that providing the necessary bandwidth to achieve acceptable quality will swamp your facilities.

Brace yourselves. Networks aren't just for data anymore. Multimedia is the watchword for the millenium. In addition to two-way videoconferencing, whiteboard collaboration, application sharing and file exchange, new demands exist for video streaming, interactive training and network telephony.

In this chapter, we primarily examine two-way videoconferencing, interactive training, collaboration tools, and video streaming. For related topics, see other chapters in NETWORK COMPUTING Online's Network Design Manual, such as Computer Telephony for the Enterprise and Building a Frame Relay Network, in the Wide Area Systems and Services section.

The first section of this chapter is a primer: How Do VT Systems Work? It describes audio- and video-compression and decompression techniques, and examines the standard algorithms that allow communication among equipment from different manufacturers. We'll focus on H.323, the International Telecommunications Union's (ITU's) architecture for "Visual Telephone Systems" and Equipment for Networks that provide a Non-Guaranteed Quality of Service. We'll also explain how the H.323 architecture accommodates H.320 (operation over ISDN) and H.324 (operation over POTS [plain old telephone system] lines).

The next section, Calling, Answering, and Managing a Conference, describes what goes on during call setup over a LAN, LAN/WAN or switched telephone network, with and without proxies, firewalls, gateways and gatekeepers. We'll help you understand bandwidth requirements and bandwidth management for different levels of performance and conference quality.

The last section, How Does the Transport Affect Conference Appearance and Performance?, covers design and scaling issues that apply to the backbone, and also identifies end-user delivery networks worthy of your consideration.

Before we jump into the primer, it's important to clarify our use of some relevant terms. Videoconferencing traditionally has been associated with "room systems", equipment placed in conference rooms for two-way audio/video meetings. Examples include high-end systems like VTEL Corp.'s 227 and PictureTel Corp.'s Concorde. Most "room systems" follow H.320 standards, have far-side camera controls, and are used for conversations that may be supplemented with document cameras and VCR feeds. By introducing gateway equipment, H.320 "room systems" can be connected to a LAN and participate in conferences with H.323 terminals.