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T1 benefits, fractional costs.


Lewis Homes Management Corp., Upland, Calif. (30 miles east of Los Angeles), develops lots of housing in the fastest-growing areas of California and Nevada.

Managing major projects simultaneously requires constant communication between corporate office and regional project offices.

Monitoring construction and sales and ensuring continuous flow of materials keeps faxes busy and the telephone lines hot.

An on-line data network links an AS400 computer in Upland to multiple terminals at four regional offices.

From Upland, multidrop analog circuits once served El Centro/Las Vegas and Sacramento/Reno.

Each regional office had a 9.6-kb/s IBM modem connected to an IBM 5394 controller, which managed data flow for the regional site's terminal devices.

As the need for additional terminals grew, a second controller was added at each regional location with a modem sharing device. Capacity strained as the number of users doubled.

Polling cycles became longer.

Response times suffered noticeably.

Multidrop topology, though easily implemented, was expensive.

Line costs for the two circuits were $4500 a month.

Lewis Homes was paying more than $19,000 per month in line costs and tolls for inter-office communications.

All Maxed Out

"We knew we had to do something fairly quickly," says Hugh Scheffy, vice president/controller for the company.

"With the amount of traffic being generated, terminals were becoming unusable at times all across the system," he adds.

Working with Jim Holmes, network-design engineer for Trident Data Systems, he investigated alternatives.

The first thing they figured out was that the traffic could not justify full T1 service to all points.

But ITI MetroMedia offered a package that included FT1 service to the three most distant sites.

To economically access these low-cost digital services required a T1 access loop to the IXC POP.

From there, discrete DS0s could be broken out by the IXC's DACS and routed via its tandem switch to the various sites.

With T1 access to the POP, point-to-point 56-kb/s digital service could be provided to Sacramento, Reno, and Las Vegas at less than $4000 a month for all three links.

Due to tariff vicissitudes, the 185-mile link to El Centro would have cost too much, so they decided to retain that leg of the 3002 circuit as a point-to-point connection.

Holmes designed a system that would take advantage of the 56-kb/s digital service to double data bandwidth to 19.2 kb/s and use the remaining bandwidth to set up four tie trunks to carry voice and fax between Upland and the three most remote regional offices.

Voice/data muxes from Pacific Communication Sciences meld the voice and data circuits onto a single DS0.

The output of each of the three voice/data muxes is fed to a DSU/CSU, then combined using a Telco Systems channel bank.

Using an enhanced network-management software package operating on a PC, each voice/data mux is addressable; it can be controlled individually, or commands can be issued globally to all units in the network.

Bandwidth allocation, line configuration, a full range of diagnostic tests, and even software/firmware upgrades can all be performed from the same terminal. The hybrid network saves Lewis Homes over $5000 a month.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Lewis Homes management Corp.'s hybrid network
Publication:Communications News
Date:Jan 1, 1991
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