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Another point worth noting: These FRADs can be a bit expensive. Our top ticket unit tips the scales at just over $11,000, as we tested it. More troubling, however, is the fact that none conforms to the FRF.11 specification for voice over frame relay, which means that interoperability won't be a reality for some time. Additionally, all of the units tested for this roundup use proprietary methods of segmenting, prioritizing and compressing voice packets.
After all the calls were placed, data collected and CMOS scores compiled, ACT Networks NetPerformer SDM-9300 took top honors. Offering the best quality voice and top-notch data throughput, the NetPerformer is tough to beat.
ACT Networks NetPerformer SDM-9300
 The best feature of NetPerformer is its voice quality. Despite the number of IP packets we blasted through the unit, NetPerformer maintained consistently higher CMOS scores. And NetPerformer provides this high quality without sacrificing too much of its data performance. To handle voice efficiently over congested links, a FRAD can segment and prioritize the voice packets over the data packets and mark data packets as discard eligible or withhold them until the voice or fax packets have been safely delivered.
Every unit we tested offers the ability to tune various voice and data attributes. NetPerformer employs an effective voice-compression algorithm along with its prioritization and segmentation methods. More packets than usual were transmitted across the frame relay circuit--even during idle moments--because of segmentation of normal FRAD-to-FRAD internal management and communication frames. These frames are much smaller (30 to 80 bytes, for example) than normal data frame
s, and produce an almost insignificant data overhead, even for large enterprise networks.
Optimizing Voice Quality
Data and voice packets were efficiently compressed and delivered between FRADs, even when there was congestion. NetPerformer's optimization schemes had a profound effect on the quality of voice received at the other end of our test network. We noticed roughly 35 percent of data frames marked discard eligible by the NetPerformer when moving IP data across the WAN at 56 Kbps. This throughput was measured while simultaneously conducting voice conversations over our circuit with a CIR (committed information rate) of 28 Kbps. Other units operated in a similar fashion, indicating they were prioritizing and segmenting voice frames effectively over the data frames. The other units performed these functions to a degree, but NetPerformer was able to achieve the best CMOS scores.
Interface Routines
Although NetPerformer does not have a GUI application for management, setting up and mai
ntaining the unit was quick and easy. ACT Networks provides a step-by-step routine to configure its attributes--such as voice properties and IP routing. But all was not perfect, and during the course of our tests we found that a few of the recommended "extended commands" were undocumented or impossible to locate.
We configured the unit to an acceptable level of performance without them, but some of these commands were important to the fine-tuning of the voice and data packetization. NetPerformer's interface didn't come close to the GUI management offered by Acclaim, but it was quicker and easier to use than Motorola's.
MICOM Communications Corp. Marathon 3K Integration Multiplexer
 MICOM's Marathon 3K Integration Multiplexer offers solid voice and data performance at a great price. Its voice quality is second only to NetPerformer. And like NetPerformer, Marathon 3K's voice performance didn't sacrifice data throughput
performance at heavy loads. Marathon 3K's data throughput wasn't as good as that of our top data performer, Motorola's Vanguard 320, but among the devices tested Marathon 3K's performance can be considered exceptional.
Awkward Interface
MICOM's configuration and management console is similar to the one offered by Motorola for its Vanguard 320. It, too, offers a text-based menu configuration for voice. However, we found its dual configuration interface awkward. The routing function for the Marathon 3K is handled separately by a plug-in card, which has its own command-line interface.
Although you can get to this interface from the main text menu and jump back when you are through, it's still confusing because each interface uses a different command syntax.
With a little practice, we were able to configure and manage the Marathon, but the process took some time to learn, and it is not as intuitive as the GUI offered by the other devices tested.
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