Timothy
Parker Consulting Incorporated
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Server-based RAS solutions Last column we discussed a small, 3-port RAS unit from MultiTech that suffices for small companies and small home businesses. As promised, we now move on to those RAS units offering up to 16 ports for either remote access or local serial use. As mentioned in previous columns, these units come in two flavors: those tied to the network and those attached to a server. Let's deal with the latter first. For the most part, server-based RAS units are seldom more than a traditional multi-port serial card with a breakout box sporting either standard DB9 or DB25 serial ports, or a set of RJ45 ports. Connecting modems to these units requires external modems and serial cables wired from the modem to the connector. Since the connectors tend to vary a little as to sex (male or female), size (DB9 or DB25), and wiring (DCE or DTE) you have to be careful choosing cables. Although some companies do market their cards specifically as modem servers, all can be used for any serial devices, including terminals, direct connections to other computers, and the usual serial devices. Before looking at these multi-port cards, a quick mention of one of my favorite solutions. Comtrol's RocketModem is a single ISA full-length card that contains either four or eight modems. Designed primarily for Windows NT, the RocketModem is notable for its complete ease of installation, configuration, and use. The RocketModem installs itself as a bank of normal COM ports. I usually use the eight-port RocketModem and install them as COM3 through COM10 since most motherboards already offer two serial ports. Multiple RocketModem can be installed in the same computer, with increasing COM port numbers. The only problem to this approach is that some applications do not recognize COM port numbers above COM4, so check applications carefully before resorting to this solution. As mentioned, the RocketModem provides either four or eight modems. The backplane has standard sockets for telephone cords, eliminating both a physical stack of modems and tangles of serial rods. For this reason alone, I like the Comtrol product: it makes server backplanes that much more tidy and manageable. The modems on the current version of the RocketModem are 33.6kbps units with fax capabilities, supporting every protocol you can think of except K56Flex (which may be available in newer RocketModems). An onboard fast CPU reduces server impact of the eight modems noticeably. Traditionally I'll install the RocketModem with some ports dedicated for incoming and outgoing network-wide fax use (there are a number of network fax packages available, as well as traditional solutions like Symantec's WinFax), and leave the rest of the ports configured for dial-in, dial-out, or combined use, depending on the network. With eight modems on the board expansion is easy if only a few lines are needed to start. The downside to the RocketModem is that your modems are fixed and can't be upgraded without replacing the whole board (not a big deal since new modem standards are unlikely in the new near future) and you're buying eight modems up front. Alternatively, a number of excellent 16-port serial port card-based systems are available (with many companies offering four and eight port versions, too). I often use units from Comtrol, Digi International, and Stallion Technologies. Perhaps the fastest of these new cards designed for RAS is from Digi. The AccelePort Xr is a plug-in multiport card. The ISA or PCI board is connected by an umbilical to either an RJ45 or DB25 breakout box supporting eight lines or a simple octopus cable with four arms terminating in eight DB25 connectors. The only documentation included with the AccelePort Xr is a single page of hardware installation instructions. Everything else is on CD-ROM as on-line manuals. Drivers for the AccelePort Xr are available for Windows 95 and Windows NT, SCO UNIX and UnixWare, NetWare, and generic SVR4 UNIX. The drivers install easily and work well with both Windows NT and SCO UNIX, my usual RAS operating systems. The ends of the octopus cable can be plugged into any standard serial device such as a modem or terminals, although extension cables will be required in many cases. The AccelePort Xr has an on-board RISC processor which speeds the processing of traffic to the point where each line can support throughput in excess of 900kbps. No modems will require that capability, but the speed does allow for convenient mixing of ISDN and analog modems, as well as fast direct connections to serial devices. Standard serial multi-port systems work just fine, despite some manufacturer's attempts to downplay them in favor of more expensive "RAS" versions. Don't fall for the ploy unless the RAS system has some features that enhance their capabilities, such as more cache RAM or better on-board CPUs. I've relied on five year old Stallion multiport cards in many servers, using the sixteen ports to drive external modems with no problems at all. Not all multiport cards support Windows NT, favoring UNIX, but a little digging and you'll find drivers for quite a few. Comtrol's RocketPort system offers excellent drivers for Windows NT with an eight-port serial break-out box, for example. Next column we catch up with network based RAS and serial port units. |
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