ISDN Videoconferencing

Many more LAN and dedicated-wire videoconferencing systems are in use than ISDN-based systems today. LAN-based systems, such as Sun's ShowMe, SGI's In Person, Insoft's Communique, Apple's QuickTime Conferencing and Intel's ProShare, can connect the telecommuter to distant LANs or the Internet via baseband Internet connections. In this configuration, the teleworker's PC, Mac or UNIX workstation can access remote resources as well as perform videoconferencing.

SGI and Sun are particularly good videoconferencing platforms since they often have the horsepower and built-in ISDN and video capture capabilities to make installation as easy (and inexpensive) as adding a camera and software to a networked workstation.

If you implement desktop videoconferencing on your LAN, beware: Ethernet was not designed for streaming audio and video traffic, and bandwidth may be a problem (although many vendors have monitoring software that keeps traffic at a safe level). Find out how much network bandwidth is consumed by the selected system, especially for multipoint systems. To check things out, take a "sniffer" snapshot of your network before and after installation. If you were maxing out your network before, it's probably not a good idea to add videoconferencing. At least monitor the network as systems are being added and isolate the traffic by keeping it on a routered segment as much as possible.

New network technology will make desktop videoconferencing less stressful. ISO-Ethernet combines 96 ISDN lines with a 10BaseT Ethernet network. Special cards and hubs keep the ISDN and 10BaseT signals separate, so connecting video over the ISDN "channels" has no effect on the Ethernet. Switched Ethernet provides 10Mbps to every desktop, and the fast Ethernet technologies (100BaseT and 100VG-AnyLAN) provide more bandwidth.

Finally, ATM might eventually be the standard for transporting multimedia communication in both the local and wide areas however, it doesn't appear so today. ATM is lossing its support to advances in Windows, Apple OSX and the many flavors of UNIX - namely Linix.

If you cannot put desktop videoconferencing systems on your network or you want very high-quality video, a number of systems, such as those from Datapoint, C-Phone and Avistar, provide excellent video (true 30fps) and collaborative capability over a dedicated "video" network. This network could be made up of coaxial, fiber or unshielded twisted-pair (UTP) cables.

Typically the LAN is used for data-sharing (whiteboard and file transfer), and the dedicated twisted-pair is used for video and audio. A video hub or switch is used to connect the desktop systems, and in some implementations can act as a "server" for phone book and network control. This device also interfaces the video network to a shared third-party codec (coder-decoder), which is used to extend the reach of the conferencing system to the wide area via a digital services such as ISDN, Switched 56, T1 and so on. Most dedicated UTP systems use analog video over the dedicated video network and rely on the codec to achieve standards (H.320) compatibility over the WAN. Unfortunately, unless you can set up a separate channel via a modem or the Internet, you may lose your collaborative tools going over the codec.

Dedicated systems are pricey, but if you need good video for meetings or training in the local area and have enough people to justify the cost, they deliver excellent results.