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Staking out ISDN's rightful place in data communications.

If you've ever mentioned ISDN around serious data people, you know how it goes. They react as if they just bit into a lemon.

Face it, ISDN's 64 kb/s B channels don't impress people who work in mega numbers, dealing with local area networks that carry anywhere from 10 to 100 Mb/s. But then, your role isn't to impress these folks, it's to help them solve problems.

The problem develops when you move away from the local area. LAN speeds are wonderful when you're in the same building or on a campus. But you can't get those speeds once you move a distance away.

To establish an inexpensive remote connection to a LAN today, either for a statellite office or a work-at-home application, in most cases you're talking use of 9.6 kb/s modems: not a speedy way to move data.

When you compare ISDN's 64 kb/s speed with 9.6 kb/s, you can see that an ISDN link from a remote site to a LAN doesn't sound so dreadfully slow after all. You also have to remember that while an Ethernet LAN may have a nominal 10 Mb/s speed, you'll rarely get that full speed out of it, and that speed may be divided up among scores of users.

These are among the points that Jeffrey Neil Fritz of West Virginia University (WVU) makes in his recent book, Sensible ISDN Data Applications.

WVU has been using ISDN to move data since 1989, and realizes that while the strategy has its limitations, it also fills a valuable niche.

"ISDN has applications that are appropriate both to heavy LAN users and casual data users," Fritz writes. "These middle ground applications hold the secret to ISDN's success.

"ISDN data excels in providing solutions for today's data communications needs which are not easily accomplished through other services. LAN extension, for example, is nearly impossible to accomplish with analog services.

"Other digital services are far too expensive to allow residential connection for work-at-home applications. The alert data communications manager will seek middle ground--deploying unique applications where ISDN's worth is clearly demonstrated."

Fritz calculates that on a 10 Mb/s Ethernet LAN, most users see real throughput of 300 kb/s by the time the bandwidth is shared among large numbers of users and throughput is limited by network interface cards and concentrators.

With data compression algorithms and sophisticated transfer protocols to boost speeds, Fritz says, single ISDN B channel throughput could reach 100 kb/s. The difference between 300 kb/s at the main office and 100 kb/s remotely isn't that significant in most applications.

WVU also tested all kinds of equipment over the years, and Fritz offers some thumbs-down and thumbs-up advice. For instance, his best choice among desk sets is the Telrad IDS 287. He says it's the only one he has found that has full 2B+D capability plus 64 kb/s sync and 38.4 kb/s async B channel communications.

Fritz's book, at 103 pages a quick afternoon read, is easy to get through and strong on laying out the problems WVU faced and how ISDN solved some of them. He also tells of the technological obstacles and glitches that accompanied the increased use of ISDN.

Sensible ISDN Data Applications is published by WVU Press, P.O. Box 6069, Morgantown, WV 26506-6069. Phone 304-293-5040. The book is $29.95.
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Integrated Services Digital Networks
Author:Tanzillo, Kevin
Publication:Communications News
Date:May 1, 1993
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