Connecting With Small Office ISDN On A Budget
By Dave Brown
Telecommuters need excellent data communications if they're to get the feeling that working from a small office/home office (SOHO) is as good as being connected directly to the enterprise. But do they really need ISDN? Is plain old telephone service (POTS) enhanced with 33.6-Kbps and 56-Kbps modems good enough?
In reality, the analog telephone network is slow and noisy. Fewer than 50 percent of circuits in the continental United States are clean enough to allow the more sophisticated modems to approach their theoretical performance levels. None of the 56-Kbps devices on the market (neither 3Com Corp.'s X2 or Rockwell International's K56flex) achieve uncompressed throughput rates greater than 45 Kbps--even on the cleanest circuits.
 Basic Rate Interface (BRI) ISDN remains an attractive alternative--if you live in an area where the service is available. It can be installed on a second pair of telephone wires in your home or small-business office (see "Typical SOHO ISDN Installation" on page 184).
The next step toward cost-effectiveness for ISDN will come in the form of Always On, Dynamic ISDN (AO/DI) service. Under that rubric, e-mail and "pushed" information feeds will travel on the "D" channel in X.25 packets. When a Web browser or any other application needs more bandwidth for heavier data downloads or graphics, one or both of the B channels will be fired up to add 64 or 128 Kbps to the session's capacity. If you take the plunge and go through ISDN's significant learning curve now, it will be a relatively small step to move up to AO/DI or dramatically higher speeds when Asymmetric Digital Subscriber Line (ADSL) becomes available in a fe
w years.
But Isn't ISDN Expensive?
ISDN is not that expensive if you do a real
istic cost-benefit analysis and put a value on the increase in productivity that high-speed telecommunications can provide. You'll need to research specific ISDN pricing for your area. Tariffs are different in most states; they may even be different among localities. Start with your local telephone company and ask for a toll-free number to a regional ISDN marketing center with consultants who can check on availability and quote exact prices for ISDN to your specific location.
Take a look at the May 15 Buyer's Guide, "Making the Connection with ISDN Routers," (page 130) and the June 1 feature, "SOHO to the Enterprise" (page 48) for discussions of routed remote LAN solutions. Although they cost more than terminal adapters (TAs), routers often are preferred because they support multiple users and can be programmed to manage connections to keep ISDN costs to a minimum. In the Buyer's Guide charts starting on page 188, we're listing 45 ISDN TAs and PC Cards from 26 manufacturers that support point-to-point con
nections from one-PC offices to enterprise servers and Internet service providers (ISPs).
Most of these devices cost less than $500 and are designed to support only one BRI line. A few can support much higher speeds. At the high-priced end, Digi International's Digi DataFire PRIme ($3,795) accepts Primary Rate Interface (PRI) ISDN (1.544 Mbps). ISDN*tek's CyberSpace Enterprise Quad Plus Card ($2,995) has plugs for four BRI lines that can be bonded to maintain a 512-Kbps connection. The same capability is available on Netaccess' Instant RAS QuAD BRI card ($2,499).
To download an Adobe Acrobat .pdf format version of the ISDN Buyer's Guide charts, click here.
Updated October 8, 1997
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