Using Windows NT RAS, I tested a beta version of the InterChangeVS 2000 in Network Computing's Syracuse University Real-World Lab® and found that the slim black box alleviates the need to add hardware to servers, and provides additional modem reporting. On the other hand, its performance could be improved.

After several days of working with the InterChangeVS 2000 on our network, I found its presence unobtrusive and liked that I could add the product without having to open up the server, insert hardware, and configure DIP switches and hardware interrupts. The software configuration was easy to manage and worked well.

Traffic Moving Smoothly Connecting the InterChangeVS 2000 is as simple as cabling it up to the phone lines and the network and turning it on. An extension of the server, the InterChangeVS 2000 requires drivers on the server so that the two devices can communicate. Adding the driver software is just like adding a network adapter in Windows NT.

After the driver software is installed, simply add the Remote Access Service that comes with NT or Routing and RAS services, which you can download from Microsoft Corp.'s Web site to NT. Because no provisions exist for workstations sharing the modems over the network, you will need to turn to third-party applications, such as Novell NetWare Connect, for network modem sharing.

The VS 2000 communicates with the NT RAS device via a proprietary Ethernet protocol. It communicates at the MAC (Media Access Control) layer, so the NT RAS and InterChangeVS 2000 must be in the same broadcast domain. After sniffing the Ethernet with a Network Associates Sniffer, I discovered that the VS 2000 is very chatty. This product encapsulates incoming modem traffic into 46-byte packets and sends them to the NT RAS device over Ethernet. The device drivers on the NT RAS take the packets and pass them to NT RAS for processing. In turn, the NT RAS device sends traffic back to the VS 2000 in 580-byte packets.

Even the transfer involves a number of small packets. However, the InterChangeVS 2000 traffic only accounted for 3 percent to 5 percent of overall network utilization during testing. In performance testing on a quiet network, the VS 2000's performance hovered around 30 Kbps. To gauge how well the modems transferred data across the network, I tested with no software compression--only V.42 compression--on the NT RAS server. After I added traffic to create about 20 percent utilization on the Ethernet protocol, performance varied only slightly.

Minimal Management Once the software is installed on a Windows NT server, programs on the server provide minimal modem management. You can test, reset and view numerous statistics about the modems, which is much more functionality than Windows NT alone offers. I set up a report to examine the hourly transmit and receive bits and to look for any errors. The report format looks like a spreadsheet, with the modem names flowing down the side and assorted statistics spanning the top. While RAS management is not the VS 2000's primary focus, I would have appreciated some functionality to query the modems for AT configuration and S Register information.

During testing, I also set up reports that wrote modem data to the test file every hour. Alternatively, I could have imported this file into a spreadsheet. For more customized reporting, I also had the option to write only the data that was presented to the screen.

Send your comments on this article to Mike Fratto at mfratto@nwc.com.