June 30, 1997
Don't ignore the fine print on ISDN
By Bob O'Donnell
Solutions that really work are a wonderful, though seemingly rare phenomenon in the
world of IT, particularly when it comes to telecommuting. This is unfortunate because more
and more workers are starting to do partial or even full-time work out of their homes or
tiny satellite offices.
Luckily, there is a robust answer for most applications and most users: ISDN. It's not
as glamorous as Asymmetrical Digital Subscriber Line, fractional T1 lines, and a host of
other oft-discussed subjects, but ISDN is available, it's relatively cost-effective (at
least, in many parts of the United States), and it works. Even better, if you've got a
dedicated connection and aren't stuck using an overburdened router, it's pretty darn fast.
In fact, in subjective tests that I've been able to enjoy recently, I'd say it feels
almost as fast as the shared T1 lines found in many corporate environments.
Getting ISDN configured with a desktop or laptop machine isn't exactly a picnic, but
new products, such as the 3Com Impact IQ terminal
adapter now permanently ensconced in my home office, are making the process easier .
Typing Service Profile Identifier numbers, selecting the appropriate telephone switch, and
other meaningless minutia will soon be a thing of the past.
But there are still some hidden gremlins in the world of ISDN, particularly if you're
hooking up external adapters to PCs Ð which I'm willing to bet is how most people use
them. The biggest issue revolves around PC serial ports. For some unknown reason, even
today's fastest Pentium II desktops are saddled with leisurely 115Kbps serial ports as a
result of the 16550 universal asynchronous receiver/transmitters (UARTs) that drive them.
Macintosh serial ports, on the other hand, have supported 230Kbps connections for years.
Ironically, the 16550-driven PC ports are sometimes referred to as "fast" ports;
I've even seen 16550-based upgrade cards touting these benefits.
But when you try to hook up an ISDN terminal adapter capable of 128Kbps or 230Kbps (via
compression), to these "fast" ports, you throw a speed bump at your ISDN line's
performance. Unless you buy a $50 or $75 serial-port card driven by the newer and truly
faster 16650 or 16750 UARTs (both of which are available as parts for less than $5), the
throughput you achieve on your ISDN line is going to be nowhere near where it should.
None of the marketing materials for external ISDN adapters are very forthcoming about
this situation. In fact, most highlight the fact that their products support as much as
230Kbps throughput but don't add that you have to add a card to achieve that speed. Only
after you open the box and see the flyers for faster serial port cards that allow you to
achieve the "true potential" of your terminal adapter do you realize what's
going on.
The problem isn't entirely with the terminal-adapter vendors. Microsoft hasn't written
drivers for the faster UARTs in either Windows 95 or Windows NT, which means you also need
to get a third-party driver if you want to use a really fast serial-port card. Also,
system manufacturers and motherboard designers seem unwilling to spend a few more dollars
to speed up the overall throughput potential of their machines. As we move into an era in
which Internet connection speeds are becoming critically important to the normal computing
experience, I find these developments disappointing and even a bit disturbing.
Thankfully, there are some good solutions. I ended up buying Pacific CommWare's 16750-based TurboExpress Port 920
ISA serial-port card and its accompanying TurboCom/95 Pro drivers, both of which have
worked very nicely. (In fact, the bundled TurboCom Re:Ports utility is a great
troubleshooting tool.) My only resentment is that I had to make the purchase at all.
Personal computer processor speeds are reaching more impressive levels everyday, but
until computer system bandwidth capabilities are raised, much of that processing power
will go to waste. And that's a real shame.
©
Copyright 1997, by InfoWorld Publishing Corp., a
subsidiary of IDG Communications, Inc. Reprinted from InfoWorld,
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