Our tests revealed that the L2W-323 can transcode audio and video to maintain a conference with no measurable degradation. RADVision's codecs operate at high enough performance to handle the loads that any of today's H.323 LAN-connected desktop videoconferencing systems are capable of generating.

Managing the Connection L2W-323 management is accomplished via a serial port using a VT-100 terminal emulator or through RADVision's configuration software, which runs on a LAN-connected PC. The software automatically discovered our L2W-323, which required a password before allowing access. After a configuration change, the state of the L2W-323 could be stored in a file on the managing PC.

Compared with the PictureTel LiveGateway, RADVision's event logging and troubleshooting is awkward. Management is accomplished using the management PC to open a telnet session on the L2W-323, and then watching the event messages roll by on the screen. If you want to capture information for later analysis, you must start and stop logging on the management PC's telnet accessory.

From a user's point of view, placing a call on the L2W-323 feels very much like dialing a telephone. DVC workstations that use H.323 LAN protocols automatically attempt to register with H.323 gateways found on their network segment (users don't have to log on to a gateway before using it). RADVision's Gatekeeper software can be set to accept registration requests from any end point or only from end points that have been predefined as members of a zone.

The software also lets you build tables of Gatekeeper IP addresses in other zones so that calls between area codes can be completed.

Making the Call To complete DVC-to-DVC calls within the enterprise LAN, the L2W-323 can operate in multiple zones, using a zone prefix that acts like a telephone area code. For example, if your zones are numbered 1, 2, 3, etc., and every DVC within a zone is assigned a specific extension number (for example, 678), then you place a call into Zone 2 by supplying the string "02678."

Service prefixes are used to distinguish calls that go off the LAN, via ISDN, to an H.320 system. For readability, an administrator can design them with multiple characters (for example, "8-" "7-" and "6-," perhaps with the meanings "8-384 Kbps H.320," "7-128 Kbps H.320," or "6-Voice call"). To place an off-LAN call, you might supply the string "7-12012221111,7-12012221112."

The L2W-323's Gatekeeper is highly configurable for directing incoming calls. Predefined services include forward, forward on busy and forward on no answer. You might point the latter two to an attended operator station. Or, with supplemental automatic call director equipment, voice greetings can be provided.

RADVision also offers specialized products for specific LAN/WAN applications. The L2W-20 accepts up to 384-Kbps direct connections to H.320 systems, encapsulating bitstreams for transmission over a LAN instead of ISDN. The VIU-323 is a self-contained terminal adapter that converts H.320 to H.323 at the point of connection to a LAN, and the MCU-323 is an unattended multipoint conferencing unit that supports up to nine simultaneous voice-only or multimedia calls. With the addition of RADVision's Gatekeeper software, the MCU-323 becomes a multipoint call control device that may supplant the L2W-323 for distributing two-way audio and video in training applications.

PictureTel Corp. LiveGateway and LiveManager

PictureTel's server-based gateway solution offers excellent performance, logging and solid management capabilities. Although LiveGateway can be set up in a pool configuration to serve an enterprisewide LAN, this solution is best-suited for workgroup environments; it's typically sold in bundles consisting of two or four LiveLAN H.323 DVC units, a LiveGateway unit and the LiveManager gatekeeper software. PictureTel offers an excellent solution if you're new to H.323 desktop videoconferencing, but have invested in H.320-based room systems.

Our testing revealed that the LiveGateway can transcode audio and video to maintain a conference with no measurable degradation. Like RADVision, PictureTel's codecs operate at a high enough capacity to handle the loads that any of today's H.323 LAN-connected desktop videoconferencing systems are capable of generating.