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Data Network Expansion Can Be Done Painlessly.

If you're a data network manager for a growing company, you know the frustration of running cable each time a new user joins the data network, of having more users than computer ports, of having multiple computers and users who need access to the information in two or more of them, connecting remote sites and on and on.

Between 1982 and 1983, our employee population at Tellabs grew from 750 to 1100--an increase of almost 50 percent. This rapid growth rate posed several challenges, not the least of which was establishing and maintaining a data communitcation network.

Prior to mid-1983, we had two large computer systems. One was used by the engineering department for software design, and the other was used by the data processing, accounting and sales administration departments for accounting and inventory recordkeeping. As our company grew, so did our collection of computers, as well as the number of users requiring access to the information stored in them.

We needed a centralized information system that was accessible to key people in every department. Little Fuss or Expense

Using a little creativity and several of our own data communication products, we were (and still are) able to expand our network as needed without a lot of fuss--or expense.

Prior to last year, when a new user requested access to one of our computers, our technicians had to run cable from the user's terminal, up through the dropped ceiling, to the computer room. When the number of requests for access reached several each week, running cable in the ceiling became increasingly tedious. And the mass of black cables running to the ceiling was a real eyesore. data/voice systems that allow us to use our existing telephone system to transmit data. Data-over-voice systems use high-frequency carrier techniques to transmit data over telephone wiring without disturbing voice signals. We used our own 310 Datavoice System; it can transmit data at speeds of up to 9600 b/s over a maximum range of 5,000 cable feet.

We no longer run cable to accommodate new users. We simply plug the user's terminal and telephone into the Datavoice system's terminal interface unit (a compact case that fits under the telephone), plug the interface unit into the telephone jack, and the user installation is complete. At the other end, in the PBX room, voice is split from data by the system's dual-channel termination unit. Voice goes to the PBX, data goes to the computer. The system allowed us to hook up 25 users in a single day without running an inch of cable.

At the rate we were adding new users, it wasn't long before we used up all our available computer ports. Yet additional departments needed access. Our Quality Assurance Department needed bill-of-material records, our Technical Marketing Services Department required proposals and other product-related data, our Publications Department needed access to customer addresses for mailing list updates, and so on.

We could have purchased larger computers, but that wasn't practical--our systems were only a year old. Another alternative would have been to purchase hardware to increase the number of ports on our computers. But this type of hardware is expensive, and there's a limit to the number of ports that can be added. Provided Own Field-Trial Site

Just about the time this problem emerged, we were testing a new data communication product offering--the 331 Xplexer, a data switching system. So we decided to field-trial the product in our own network. We used the Xplexer as a port selector to allow a given number of users to share a smaller number of ports. Capitalizing on the premise that not all users wil use the computer at the same time, the Xplexer functions as a network time-sharing device. When a user wixhes to access a computer, he or she dials up the computer and is switched to an available port. If all ports are busy, the user is placed in a queue until a port becomes available.

The Xplexer solved our problem economically and efficiently. We grouped users according to department and according to expected frequency of usage, and we assigned ports accordingly. If we want to rearrange groups or assign new users to groups, it's simple. The Xplexer is menu-driven and can be reconfigured from the network manager's terminal.

When our family of computers grew from two to five, we found that quite a few users access to the information in more than one computer. Had we used dedicated terminals, those users would have needed a separate terminal for each computer they wished to access. But that wasn't practical in terms of economy or space.

Again, the Xplexer solved our problem. In addition to being a port selector, it's a data switch that permits users who require access to more than one computer to simply dial up the appropriate computer from any terminal in the network. Password protection lets us restrict access to confidential information. Reduced Lines to New Facility Last year, we completed the construction of a new engineering facility located adjacent to corporate headquarters in Lisle, Illinois. When the engineering department moved from headquarters to the new facility, another data networking problem was created: users in the headquarters building required access to the computers in the engineering building. Of course, running cable from each terminal at headquarters across (or under) a section of parking lot to the engineering building was not practical. We solved this problem by using a combination of statistical multiplexers (Tellabas 330 Dataplexers) and 331 Xplexers.

Dataplexers allow many lines to be multiplexed, or concentrated, onto a single link. The Xplexer is a statistical multiplexer as well as a data switch, so we use it in applications that require both multiplexing and switching. These products allowed us to greatly reduce the number of links required to provide users at headquarters with access to engineering's computers.

In addition to solving the urgent problems just described, the Xplexer provided other capabilities that have increased our efficiency. It allows users in different departments to share printers, thereby reducing equipment costs. It allows the writers in our Corporate Communications Department to access a computer for word processing and to transfer documents electronically to our typesetter, saving the time ordinarily required to key in user manuals and other documents. It allows our users to share the modem pool, again reducing equipment costs. We're currently planning to use Dataplexers and Xplexers to provide enhanced network capabilities to users at our regional locations in Florida, Nevada and Connecticut, and to our Canadian headquarters near Toronto.
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Copyright 1984 Gale, Cengage Learning. All rights reserved.

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Author:Ghebelian, M.; King, T.
Publication:Communications News
Date:Dec 1, 1984
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