Vision of videoconferencing

Take a relatively immature technology and subject it to extremely rapid growth, and you're bound to encounter problems. That's the state of videoconferencing today. Cost of implementation, call reliability, image quality, network stability and interoperability among multiple vendors' products remain obstacles in the path of successful deployment.

Today, the majority of business-quality videoconferencing takes place over ISDN lines. In the future, we'll see IP take over more teleconferencing traffic, while plain old telephone service (POTS) videoconferencing will likely remain a consumer-only application.

Migration to LAN-based videoconferencing raises new concerns for telecom and IT managers worried as much about LAN performance as conference quality. To capture the corporate market, vendors have devised comprehensive workgroup videoconferencing systems that promise to simplify configuration and operation.

But local conditions aren't the only issues facing network managers. Moving from the LAN to the WAN using the Internet adds another set of problems, the foremost being quality. If you've experienced video over the Internet, you probably saw something that looked like a familiar face on the other end, little or no motion and broken audio - essentially, a pretty useless business tool. The unfortunate reality is that today's public Internet is no place for real-time traffic.

The International Telecommunication Union (ITU) has attempted to improve video over the Internet. In 1995, the ITU ratified the H.323 standard for video over IP transport. Since then, the standard has been refined, improved and adjusted to work with changing LAN landscapes, but the core standard is designed for a far more constant bandwidth environment.

ITU's H.323 standard is just one of its videoconferencing standards. H.320 covers ISDN, which has the widest installed base right now.

H.324 covers POTS video, which is unable to deliver the quality that business conferences demand.

H.310/H.321 covers ATM. For sites with an ATM network, ATM video is an excellent solution. ATM's bandwidth allocation features are well-suited for carrying real-time traffic.

The momentum, however, is clearly behind IP videoconferencing. Users are beginning to look at IP video for the same reason they look at voice over IP - to try and bring down telecom charges. Calls over ISDN can cost a bundle.

Making IP work

IP video can make sense as a corporate solution if all the correct pieces are in place. The first consideration is clearly bandwidth because the available bits determine audio and video quality. You need to consider how many simultaneous calls are likely. A 100Base-T backbone is the minimum requirement if many simultaneous calls are expected. It's not hard to imagine outgrowing the 100M bit/sec backbone quickly, particularly in larger organizations.

Video technology has reached the point where, given proper bandwidth, image quality can beat that of broadcast television. Maximum frame rate is a feature that users have come to equate with video quality. Frame rate defines how many times the screen can be redrawn in a single second. While this is a contributing factor to video quality, it is not the sole definition. A system that can support 30 frames per second may only do so when there is little motion on the screen. Also, if resolution is poor, how fast images are being pushed through the pipeline is irrelevant.

The average video call requires about 700K bit/sec to run at acceptable levels. The real concern is when users start using the technology en masse. Communi-cating with remote sites is problematic, as most organizations have limited bandwidth over the wide area.

One alternative for communicating with distant locations is through ISDN gateways. These devices can convert H.323 LAN systems to H.320 ISDN and call out to circuit-switched locations. This gives users the flexibility of H.320 compatibility as well as the option of dial-up access to remote locations.

A many-tiered market

Videoconferencing systems differ dramatically in price. On the low end are incomplete packages that require a multimedia PC. When you are supplying the PC, be sure to provide the optimal configuration for the processor, memory and operating system.

On the higher end are turnkey solutions that include a PC and all the trimmings. These so-called workgroup systems are generally better suited for conference rooms than for desktops.

A third type of system is the portable unit. These systems are self-contained like workgroup systems but are generally not PC-based and are specifically engineered for mobility. Some are as light as five or 10 pounds. They typically require a monitor or TV, and some require a separate inverse multiplexer for high data-rate calls.

Look for a product that offers T.120 data sharing, especially with IP-based systems. These let you transfer files, share applications and perform whiteboard functions during conferences. Microsoft's NetMeeting is becoming the most frequently used data-sharing tool, but software such as DataBeam's FarSite and Picture-Tel's LiveShare are also good solutions. Be careful, however - though the technologies are based on a standard, T.120 products are not always compatible.

Videoconferencing was once a market dominated by one or two endpoint vendors, but those days are over. Looking ahead, we expect more vendors to develop IP-based video solutions as demand increases. Workgroup systems will dominate the market; legacy and new systems will continue to evolve and support multiple transport algorithms. Network managers, prepare for heightened videoconferencing traffic.

RELATED LINKS

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