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Dial-up network control comes of age.


As datacomm environments become more complex, users are discovering a greater need for network control.

Network-control systems spurred leased-line modem and T1 markets.

Dial-up network needs were largely unmet until recent advances provided inteligent networks that allow for a new realm of possibilities.

In the past, dial-up modems were never thought of as a major access point to networks or an alternative to leased-line modems, primarily for three reasons:

* They were slower than leased-line modems.

* Poor line quality held down maximum speeds.

* They lacked central control.

These shortcomings have now been solved by a new generation of dial-up modems.

Speed And Accuracy

Dial-up modems were originally limited to 300-2400 b/s, but new data-compression techniques such as MNP Level 5 broke the speed barrier to achieve reliable transmission at 19.2 kb/5--a feat previously associated with leased-line modems.

Helping matters further, the CCITT (an international standards-setting organization) is evaluating a new compression standard, V.42bis, which would nearly triple dial-up modem speed and ensure greater intervendor compatibility.

After three years of bitter fighting among modem vendors, the CCITT in 1988 approved the recommendation for V.42, the first international error-correcting standard for all dial-up modems.

With V.42 in place, modem vendors who in the past promoted their own method for error control will be forced to incorporate the new standard in their modems or face obsolescence.

V.42 will enable dial-up modems to overcome their biggest limitation, errors caused by poor line quality.

Other technologies make dial-up modems even more reliable:

* Trellis code Modulation improves connections by improving the signal-to-noise ratio, speeding transmission by reducing the need to retransmit data.

* Viterbi decoding demodulates the Trellis-encoded signal.

The best of today's dial-up modesm let you run advanced diagnostics on modems at local or remote sites, eliminating the need for expensive technicians in place.

The new capabilities of dial-up modems hav provided users with many new applications for these modems as part of "intelligent" central-site systems.

Over the next three years, the central-site modem market will grow at 18%, while the stand-alone market grows only 9%.


Because intelligent central-site systems let you do a lot of things:

* Test a rack of more than 500 modems from one site. It's now easier to administer and service a large installation of devices from one place.

* Monitor the status of any modem in the network. You're aware of any potential network-device problems before they reach the end user.

* Manage multiple resources such as dial, leased, and digital products all in one system. It's hard to manage multiple resources in separate chasses. Computer room floor space is at a premium. A single chassis saves space.

* Save big money. Dial lines let you eliminate the need to rent a 9600-b/s leased line. Dial-up V.32 modems cost you less than an analog leased line or DDS (AT&T's Dataphone Digital Service Network) 9.6kb/s data line. Daily connect time for San Francisco to New York is 4.16 hours or less; if it's more, dial-up loses cost-effectiveness.

* configure modems. Users can configure one modem and copy the configuration, through the controller, to all like modems in a second. You no longer have to manually configure each modem.

* Receive alarms from equipment in the system. Find and verify problems before they reach the end user.

* Run nondisruptive hardware health checks. You get info about faulty modems or phone-line problems. If a business has a rotary system, people trying to access a modem may run into one that won't answer and won't shift to another. an intelligent chassis lets you "busy out" that modem while the user goes to another.

When you want to add new firmware, tell the modems to busy out when their current call is done. save users the frustration of calling into a modem system that rings and never answers. Users get a busy signal and can try calling back again. after you finish your work, the modems are available for use.

* Provide inventory control. Many systems let you keep an inventory of all products in the chassis. You don't have to take each modem card out every time inventory is taken to check the serial number, etc. Inventory management takes place at the central site, so you need only one person to do it. That means more efficient asset management.

* Lock cofigurations. Users must occasionally alter a modem's configuration to work with a particular application. The lock-configuration capability ensures that once users have completed their applications, the configuration reverts to its original setting.

Using Central-Site Nets

Specific applications for intelligent central-site modem networks include centralized host-based applications.

One example of this is remote data collection or unattended polling.

During off hours, when phone rates are low, you can originate a call to several of your remote sites, through an intelligent chassis, to collect data on inventory, sales, etc.

Point of sale (Pos) is another centralized host-based applications.

In addition to traditional POS applications, intelligent chassis systems make retial store customer credit-card verification easier and more profitable.

Sales people use a customer's card to access the host computer at the credit-card company.

At the host site, a number of intelligent chasses filled with modems answers these hundreds of calls.

Successful calls are extremely vital.

Many stores will not approve a purchase without a successful verification of the purchaser's credit.

An unsuccessful call means a lost sale both to the store and to the credit-card company.

Intelligent chassis systems make communications with the host significantly more reliable.

If a power supply fails, the intelligent chassis can send an alarm to the data-communications manager's terminal.

Or else the intelligent chassis can send an alarm to the chassis controller display.

With the chassis, the data-communications manager can conduct tests on the products in the chassis during off hours so that they'll be ready to go at 8 a.m. when regular business hours begin and most accessing is done.

Modem Pooling

Companies formerly purchased a modem for each potential user.

Today, companies can better utilize their resources by sharing modems in an interligent chassis and creating modem pools.

These consist normally of about 30-50 modems per 100 users.

The determination depends upon usage at your company, of course.

Users signal through the company's PBX (private branch exchange) that a modem is needed.

The system links the users with the modem.

After the modem is used, the system returns to the pool for use by another user.

What about the future?

Further developments in dial-up modem technology will continue to broaden the scope of user applications.

As dial-up modems become more powerful, the industry will see them replace more and more functions formerly associated with leased lines.
COPYRIGHT 1990 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Likier, Marty
Publication:Communications News
Date:Feb 1, 1990
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