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To view the Report card.Video and data traffic can be multiplexed across a frame relay backbone at Layer 2--encapsulated directly as frame relay frames--or at Layer 3-- wrapped up in IP packets. Direct frame relay encapsulation provides maximum control over WAN delivery, whereas video over IP is more versatile and is independent of the underlying network. Either approach demands well-engineered networks. Disturbances caused by a poorly planned, equipped or managed network will pull the plug on videoconferencing instantaneously.

It's this specter of unreliable service that has delayed adoption of what otherwise would be a very attractive, cost-effective solution. Many IS managers won't consider an application that isn't supported by their equipment vendor, and bundled video solutions for frame relay are available from only a handful of companies: ABL Canada, ACT Networks, Memotec Communications and Motorola.

Our Test Focus
To get a clearer picture of the job these solutions do, we brought three of these vendors' products into our Real-World Labs®--unfortunately, we were unable to get Motorola's Vanguard 6560 MPRouter Pro, shipped from Canada, through U.S. Customs in time to include it. Motorola says the Vanguard 6560 MPRouter Pro supports high-quality videoconferencing via a V.35 serial interface, with onboard video framing. However, it does not yet support H.320, and works only with VTEL's HDLC (High-Level Data Link Control) protocol. Thus, it would not have operated with the PictureTel reference platform we used in our tests. We did, however, get a look at Motorola's Remote VU, a low-end solution suitable for low-bandwidth applications, such as remote surveillance (see "RemoteVU: High Quality at the Low End," page 54).

Some users may be tempted by video over IP, since it offers more flexibility than any frame relay-specific solution. But you'd best tread carefully around this option: Consider it only if your IP network can meet the tight quality of service (QoS) requirements necessary for videoconferencing--and that's a big "if." For a real-world view of video over IP as a frame relay alternative, we also tested the RADVision VIU-323 H.323/H.320 transcoder.

An investment in either the Layer 2 or Layer 3 approach can generate an astonishingly quick payback. Because frame relay pricing is not sensitive to distance, the payback occurs even faster between more remote locations. For example, a three-hour connection between New York and Los Angeles using 384K ISDN Switched Digital Services (FCC Tariff #4) would cost $800. With frame relay, you could nail up the call all month long for the same price.

Our tests focused on the role of the FRAD (frame relay access device), because it operates at the most critical point in the network--the interface between the WAN and your site. It's your traffic cop when unruly, bursty applications threaten to cut off video calls.

The bottom line: Videoconferencing can work beautifully over frame relay--but only if you carefully select and configure your equipment. Pay close attention to traffic prioritization and bandwidth allocation, and be sure you correctly allocate CIRs (Committed Information Rates) across the WAN.