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MMCX is both less and more than a native H.323 MCU. We tested it as a promising implementation of the H.323 holy grail--universal connectivity. It aims to support any H.323-compliant desktop device or IP phone, H.320 ISDN conferencing system, proprietary PBX digital set, and cellular or analog telephone that is accessible through the PSTN. The MMCX is an inverse multiplexer, gatekeeper and gateway with transcoding rolled into one box, and connection points for a TCP/IP LAN, Primary Rate ISDN and Definity PBX--and it's aggressively priced by the port ($500 per connection).

However, assessed purely as an H.323 MCU, the MMCX falls short. We found it capable of registering and connecting two Intel ProShare 500s, because the PS500 can adapt to G.711 audio and H.261 video, the only algorithms the MMCX can handle. But it can't function with NetMeeting 3.01, and it can only support multipoint to three or more connections if the endpoints run proprietary MMCX client software that requires a full-duplex sound card.

MMCX is on a traditional track for support and management. It requires a Unix-fluent guru to set up and provision the system, but the rack-mountable server can be tucked away in a wiring closet for 24x7 operation. MMCX hardware can be managed and monitored using a 3.0 or later Web browser from anywhere on the network.

Lucent will have a winner if MMCX software can be upgraded to support H.323 V.2, and provide multipoint service among true H.323 endpoints.

Lucent MultiMedia Communications Exchange (MMCX), starts at $18,500, Lucent Technologies, (800) 821-8204, (800) 247-7000. www.lucent.com/dns

RadVision MCU-323 V1.5

The rack-mountable device we tested also includes a hardware implementation of the RadVision gatekeeper, GK V1.2.8. As an MCU, the RadVision solution is unsophisticated and rather simple. The MCU cooperates with the gatekeeper to manage numeric-coded service classes, such as 80 = 128 Kbps participants, 81 = 256 Kbps, 82 = 384 Kbps and so on. To join a conference, the endpoint user enters a hybrid number--the first two digits represent a service class, and the next four or more represent a numeric "pass code" to identify the desired conference.

Conference services are limited. The MCU only provides video follows voice support of G.711 audio and H.261 video. If the endpoints will honor certain H.323 control commands, RadVision will impose device-level bandwidth limits specified in the conference's service class. If necessary, an operator can work through an "advanced" command-line interface in the ONLAN 323 device-management software from anywhere on the network; it allows the operator to adjust low-level parameters that control voice-activated switching thresholds, dwell times on current views and more. For a trained network technician, all RadVision elements are "tweakable."

If you have a significant investment in H.320 videoconferencing systems, one benefit of the RadVision MCU is it works well with devices such as the LIU-323, which also incorporates a RadVision gatekeeper. The LIU-323, which also is private-labeled by Madge Networks, is a widely deployed H.323/H.320 gateway device. We tested the Rad-

Vision MCU-323 on a network that included an LIU-323 packaged as a Madge LVG EN LAN Video Gateway (see "How We Tested," page 82). They coexisted beautifully. RadVision's design uses common gatekeepers set up in zoned neighborhoods, which operate like area codes for local or cross-campus call management.

For organizations with investments in RadVision hardware gatekeepers, we had special tests directing all the server-based MCUs to ignore their own gatekeepers and use RadVision's as a central service. We uncovered some suspicious registration failures all the affected manufacturers are investigating. (For details, see "Gatekeeper and Endpoint Side Tests," at www.networkcomputing.com/1018/1018f3side3.html.)

For organizations that may wish to adopt a uniform gatekeeper to support diverse H.323 devices, we tested RadVision's new NGK-100 package, a robust software implementation of the RadVision gatekeeper. We found it to be fully compatible and interoperable with hardware versions--and it experienced the same registration failures. But the NGK-100 software offers a much improved operator's GUI, compared with the ONLAN 323 software that controls hardware implementations.

RadVision MCU-323 Multipoint Conferencing Unit, $22,500 for a 15-user license, (201) 529-4300; fax (201) 529-3516. www.radvision.com or info@radvision.com

Dave Brown is an independent consultant in network design and videoconferencing. Send comments on this article to

him at Dave@dbec.com.