Modem pooling in an Ethernet network

Many small businesses need access to the Internet but find the cost of a dedicated line prohibitive. The alternatives are to have an extra phone line and a modem at every desk or to implement a method for sharing modems and phone lines among users on an as-needed basis. LantraServer from Stallion Technologies is a standalone device that lets Windows NT Workstation, NT Server, and Windows 95 users share up to eight modems or other serial devices in an Ethernet network.

LantraServer, which is slightly bigger than my Day-Timer, is an Ethernet device initially developed for UNIX platforms. In early 1997, Stallion released its port driver for NT. After you configure LantraServer with an IP address and define the server's COM ports, the port driver makes these Ethernet-based COM ports visible to any NT system running Remote Access Service (RAS).

Although LantraServer supports a variety of serial devices, my testing focused specifically on configuring and sharing modems with network-based systems. The test bed consisted of two Intel NT 4.0 servers with Service Pack (SP) 3, RAS, and Dial-Up Networking (DUN). One server had an internal modem. Installing LantraServer was straightforward because of its clearly written documentation.

Configuring LantraServer
LantraServer configuration is a four-step procedure. First, you assign an IP address and network mask to the server and reset the device to store the new IP settings. To set the IP address, use the supplied cable to connect port 1 on LantraServer to a serial port on an NT server. Next, from Start, Programs, Accessories, Hyperterminal, execute the HyperTerminal application. Now, connect to the serial port, plug in the power cord to LantraServer, reset the device, and wait for the LantraServer to time out. LantraServer tries to acquire an address automatically via BOOTP and RARP but fails. After pressing Enter a couple of times, you see a prompt to enter the IP address and subnet mask, as shown in Screen 1. Next, ping LantraServer to verify its presence on the network. You might want to add a name for this device to your Domain Name System (DNS) table so that you can ping it by name and address.

Second, configure the ports you want to use as remote NT COM ports with Stallion's Web-based LantraServer Setup utility. Start your browser and enter the IP address you assigned to the server in the previous step (e.g., Select all the COM ports you plan to use remotely and click Configure. These simple steps complete LantraServer's network and remote port configuration.

Third, use the Network Extensible Remote Port (NERP) driver to make the network-based ports visible to NT. Install NERP as a network service from the floppy that ships with LantraServer, and follow the simple prompts to configure the ports that you will attach modems to. Reboot your system to load the NERP driver. This step also adds a NERP Manager icon to the Control Panel. The NERP Manager displays the status, settings, and configuration of the remote ports; lets you add and remove ports; and monitors port activity when connections are active. When you change the configuration or add or remove ports, be sure to restart the NERP driver, which takes only a few seconds and works every time.

Fourth, if you want mobile users to call in to the modem pool, you need to include the newly created COM ports in RAS. You can install RAS and include the COM ports as part of the RAS installation procedure. If you already loaded RAS, modify the service to include the new ports by installing new modems on the COM ports defined in the previous step. You must reboot to complete the RAS and remote COM port installation. If you have more than one RAS server that will access or manage remote modems, be sure that you allocate separate ports to each RAS server (e.g., COM4-COM7 on one server and COM8-COM11 on the other).

Following these simple steps, I completed LantraServer's network and remote port configuration. After I configured the remote ports in RAS, creating new DUN connections that selected one of the new COM ports was a snap. The drop-down list of available modems included the remote ports, and calling out was easy. The dial-in side was just as easy. I had one server with an internal modem call the server with the remote modems (configured to take incoming calls), and the connection was established immediately.

LantraServer is easy to configure. The NERP driver 1.01 works flawlessly when you're making remote ports visible to RAS. I consider this capability a great accomplishment because I have fought with RAS and modem ports repeatedly over the years. The Web-based setup and configuration utility is a nice touch and a great improvement over a UNIX-style command-line interface.

To improve LantraServer, I have a few suggestions for Stallion. One change is critical and three other changes would be nice to have.

The critical change relates to the absence of an uninstall program for the NERP driver. During testing, I installed the NERP port driver on three systems. To my dismay, after I removed the NERP network service, I had to manually delete files from the system root (winnt\system32\nerp.hlp, nerpcfg.dll, nerpmgr.cpl, nerpmgr.exe). Also, the NERP icon remained in my Control Panel after I removed the service. It took a few more minutes to locate and remove the Stallion Registry keys (HKLM\Software\Stallion) and the Control Panel applet in HKLM\Software\Microsoft\Ncpa. This oversight is major, and Stallion needs to correct it as soon as possible.

My first suggestion in the nice-to-have category is to include a power switch on LantraServer. Currently, the only way to power down the unit is to unplug the power cord and plug it back in. I had to power down a couple of times during the testing process.

Second, you cannot minimize the NERP Manager applet—it is either open or closed. During testing, I repeatedly opened and closed the applet; I would have preferred to minimize it while I was adding, removing, monitoring, and changing port configurations.

Third, the written documentation and text in the Web Setup utility reflect a strong UNIX orientation. Many NT users have never worked on a UNIX platform and will find the terminology confusing or misleading. Links from the Help subscreens back to the main Help screen would make finding information easier for new users.

A Convenient Device
LantraServer is a convenient way to manage eight modems, although I expect performance of network-based serial ports to lag behind multiport modem boards that plug directly into EISA or PCI slots. If you buy this product, remember to load the NERP driver on each system that will use a remote modem for dial-out access.

To leverage LantraServer, you can activate Multilink Point-to-Point Protocol (MPPP) in RAS and let remote users connect at much higher speeds using the same modem pool. This activation requires that the remote users have two modems and an MPPP client. I did not test MPPP, but this protocol seems like a logical way to extend the power of modem pooling for higher speed connections. For details on how to configure MPPP, see my article, "Tech Stories from the Trenches," December 1997.

Contact: Stallion Technologies 408-477-0440 or 800-347-7979