After a week with this switch, we can understand why a GDC representative handles the installation and configuration duties for these devices. The APEX MAC1's modular architecture lets cards and software be shared up and down the entire APEX family of switches, which starts with the MAC1 we tested and moves all the way up to the high-density, carrier-class APEX DV2. Unfortunately, the MAC1 lugs a lot of heavy administrative baggage from the larger systems, and we can't recommend it for the low end.

As you might expect from a device of this class, the APEX MAC1 performed quite well in our tests. Data performance was good, with throughput matching that of the Mariposa ATX-100 with lower latency for larger packet sizes (1,024 bytes and greater). Voice quality also was good, though we detected some hiss using the 8-Kbps G.729A codec.

The APEX MAC1 uses ATM Adaptation Layer 2 to encapsulate voice traffic, and voice efficiency was quite good. In particular, voice activity detection features reduced typical conversation loads dramatically, consuming only 2 to 5 cells in the direction toward the talking party. These features kicked in much faster than on any other tested unit.

Although the data performance was generally good, we were disturbed that the devices would occasionally cease to pass traffic under load (see "GDC APEX MAC1: Instability Under Load," above). This behavior repeated itself several times during our testing. It was likely due to the shaper settings used during the test and could potentially be configured out--but we didn't encounter this problem with any other device we tested.

Lucent Technologies PacketStar Access Concentrator 10
The PacketStar product team was the first to successfully ship a low-cost ATM access concentrator with a T1 network interface, but now it's struggling to keep up with the rest of the crowd. Its two-year-old unit is showing signs of age. We suspect the company's recent acquisition history is largely to blame. The product was originally developed as the VR 1000 by Data Labs, which was acquired by Yurie Systems in November 1997. Six months later, Lucent spent around a billion dollars to buy Yurie.

But so far, Lucent has done little to update the PacketStar, and the resulting stagnation is causing the company to blow its lead in this market. The software on our test units still displayed the Yurie label, as did much of the documentation. In fact, a good deal of it is still labeled Data Labs. That aside, many of the features found in our other test units--voice compression, SVC support and fax recognition--aren't available in the PacketStar. Until Lucent addresses these shortcomings and demonstrates better data performance, we can't recommend this product. We expect Lucent to bring the PacketStar up to date by year's end.

In our tests, the PacketStar exhibited lackluster performance, consistently delivering the lowest throughput of any device. We detected some echo on the voice calls; the PacketStar does not perform echo cancellation. We also experienced problems getting the PacketStar to seize a channel for voice calls, resulting in dead air or busy signals at the call originator.

The PacketStar is configured through a primitive command-line interface, with no ability to refresh itself automatically for alarm-monitoring purposes.

The most troubling aspect of our Lucent experience was our difficulty in getting technical support through normal channels. When we called the Netcare Service Center and mentioned that the unit had a voice port, the representative referred us to a voice service line. But when we called the voice support number back, we were told Lucent had no record of the product in its database. Finally, we gave up and called the product management team, which arranged to get us technical support on the device.

Physically, the PacketStar is available in two models--it comes standard with a T1 ATM UNI port, Ethernet port and two slots. The PacketStar Access Concentrator 10x is two PacketStar Access Concentrator 10s stacked on top of each other, sharing some components but remaining effectively partitioned.

The PacketStar's one bright spot is its price. Listing at $7,290, it's the least expensive of this group. Unlike the Mariposa device, it supports Frame Relay Network and Service Interworking (FRF.5 and FRF.8). It also supports IP routing, using static routing only.

Send your comments on this article to David Willis at dwillis@nwc.com.