Videoconferencing over an enterprise IP network is very appealing. It makes better use of an organization's funds rather than sinking additional investments in ISDN lines. ISDN has been the only reliable way to connect video-enabled workstations and conference-room-based systems, however, the technology isn't readily available in many parts of the country, and it's still expensive.

To view the Report card. But, solid H.323-standard LAN-operable DVC (desktop videoconferencing) solutions are here. Intel Corp.'s Business Videoconferencing System and PictureTel Corp.'s LiveLAN are the two market-leading systems in this space, and we found them to be bandwidth-conscious.

The H.323 standards architecture is broad. It specifies gateways and gatekeepers that enable connections among LAN-based DVC units, ISDN-connected H.320 units, analog telephone-connected H.324 devices, and ISDN and POTS telephones. One rapidly emerging branch of this market includes gateway and billing server systems devoted to Internet telephony.

At Network Computing's University of Wisconsin-Madison lab, we tested a new class of product in this market: the H.323 video gateway. These devices transcode H.323 on a LAN to H.320 on the WAN. We tested PictureTel's LiveGateway 3.0 and RADVision's OnLAN L2W-323 Gateway. First Virtual Corp. has announced a gateway, the VGate, but it was not available in time for our testing. Madge Networks also offers a unit. However, it's a private-labeled RADVision L2W-323 Gateway.

Meeting Our Expectations We expect videoconferencing solutions to pass "executive muster." Pictures must look good, even when enlarged to full screen on a desktop system or on a 35-inch (or larger) monitor in a room-based system. All of our testing was conducted at 352x288 pixels or full CIF (Common Intermediate Format), which is the high-sharpness standard in H.320 and H.323 systems.

We also expect high-quality audio that doesn't degrade video performance. This suggests the use of the new G.723 audio-encoding and H.263 video-coding protocols, defined in the H.323 suite. G.723 requires about 16 Kbps for audio and leaves the rest of the available bandwidth for video. On the other end of a connection, a gateway usually is confronted with an H.320 system that uses H.261 video and the lowest-common denominator 64-Kbps G.711 audio standard. Therefore, a gateway must transcode the protocols on the fly without introducing noticeable delays. The two units we tested met our expectations.

The PictureTel LiveGateway and RADVision L2W-323 are distinctly different devices, but each earns high marks when measured against the requirements of the market niches for which it was developed; RADVision's solution is a rack-mountable unit naturally suited for operating one or more video PBXes in a large enterprise. PictureTel's NT-supported individual adapter cards are designed primarily for a workgroup setting. Both systems have more than adequate internal processors that transcoded the fastest audio/video streams our test H.323 DVC terminals could generate.

RADVision OnLAN L2W-323 Gateway

We liked this PBX-like rack-mountable system for its industrial-strength design and control features, which can help you protect mission-critical enterprise applications from H.323 traffic. The OnLAN L2W-323 can handle call routing and limit unauthorized access. It offers interfaces to user applications for automatic call direction, billing and call detail reports using a simple API that hides the details of H.323.