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Browser-Based Conference Management
An encouraging software development strategy being adopted by these H.323 MCU manufacturers is to use standard Internet browsers (we ran our tests with Microsoft's Internet Explorer 4.0 with Service Pack 1 and Netscape Communications Corp.'s Netscape Communicator 4.6.1), not only for conference administration and scheduling, but for direct control and monitoring of the MCUs and gatekeepers. This usually means that MCU server equipment can be tucked away in a wiring closet, and still be managed from anywhere on the intranet by conference administrators.

Sophisticated Java-based Web design techniques are used by the three manufacturers that host their MCUs on Windows NT 4.0 Server systems: PictureTel, White Pine and VideoServer. To accommodate the PictureTel 330, we had to upgrade to Microsoft Internet Information Server (IIS) 4.0, and use Sun Java 1.01 plug-ins. (We also had to work around a Microsoft installation bug in IIS 4.0; the details are in "Side Tests of H.323 Gatekeepers and Endpoints" at www.networkcomputing.com/1018/1018f3side3.html). Then, to accommodate an early beta release of White Pine's MeetingPoint 4.0, we had to install the Java 1.1.1 plug-ins. Note that White Pine's "gold" release in early July eliminated that requirement.

Gatekeeper Gaffes
An important architectural component of H.323 that may be new to operators of ISDN-supported H.320 systems is the gatekeeper. In switched-circuit telephony systems, endpoints are hardwired to a "phone number." On a LAN, endpoint devices can disappear and reappear with dynamically assigned IP addresses. One or more gatekeepers must be available on the network to register and remember current locator information about each endpoint. Three important pieces of information can be supplied: the current IP address (e.g., 100.201.102.203), an E.164 ID (a few numeric digits or a full North America dialing plan number that can be sent through a gateway for connections with H.320 endpoints); and an alias--a string of characters that may resemble a name or e-mail address. A gatekeeper simplifies the process of calling from one H.323 endpoint to an MCU or another endpoint. You can specify who it is you want to reach with an easy-to-remember name or extension number.

The most vexing problems we encountered while testing these H.323 MCUs involved noncompliance with capabilities exchanges, or erroneous registration, admissions and status (RAS) signaling among endpoints, MCUs and gatekeepers. The H.323 architecture provides a rich, elaborate behind-the-scenes language for setup, capabilities exchange and control among participating H.323 devices. This summer, we saw all the participants failing in one way or another to agree on capabilities exchange requests, or making confusing mistakes in registration syntax and grammar. However, we believe that the major manufacturers will have most of these problems resolved in new software versions released this fall, or by early next year.

You can protect yourself by fully investigating the audio and video codec options supported by a prospective MCU manufacturer, and then testing the actual endpoint hardware and software you plan to use for your most important videoconferences.

MCU Categories
Under the H.323 architecture, two design approaches may be followed: Decentralized MCU requires all participants to multicast to one another. This avoids concentrations of video traffic on some segments of a network, but requires a distracting form of "baton passing" to manage a conference. Centralized MCU is the approach used by all manufacturers whose products we tested. All endpoints send their video to a designated MCU, which selects the party that is talking, and sends that video back to the others.

However, central-design MCUs can be cascaded to reach groups of participants, and a form of decentralization can be achieved by placing them in different segments of the enterprise network. White Pine, for example, designed MeetingPoint to support hundreds of simultaneous conferees, up to 25 per MCU. Standalone servers, operating in linked domains, copy the presentation generated in a head server, where the conference is managed.

Our grades reflect our belief that, although designs are distinctly different, each type of H.323 MCU has something to offer. Buyers have intriguing trade-offs among price, reliability and feature sets. The yardsticks we use depend on implementation category.

Rack-mounted solutions may best serve an organization that views videoconferencing as a utility to be managed by a technical staff well-versed in telephony and comfortable with Unix-like command structure interfaces. But once configured, Lucent and RadVision equipment can be left alone 24x7 in a wiring closet and managed with PC software from anywhere on the network.

Of the server-based solutions, VideoServer Encounter NetServer most closely resembles the utility model. The only contender to offer mixed-mode (audio and video) conference management, it gains performance by manufacturing its own server case, which accommodates up to four MCU hardware boards. Lower-cost PictureTel NetConference and White Pine MeetingPoint software-only implementations use appropriate Windows NT 4.0 servers that you can buy or may already have.

There's a danger in do-it-yourself MCU deployments with apparently lower up-front prices. Post-installation support and the need to deal with poorly met user expectations can cost plenty. Encounter includes installation and the first year of maintenance in its price structure, which we convert to "cost per (videoconference) seat" in our features table (page 96).

To make NetConference and MeetingPoint somewhat comparable, we added the estimated cost of server hardware to each manufacturer's software license prices: $1,200 for eight to 10 users, and $2,000 for 24 or 25 users.