Expandable LAN Simplifies Insurer's Data Processing.
Until very recently, the Tampa facility was located in a three-building complex, where staff handled inquiries primarily by telephone. The inquiries concerned opening new insurance polices, status changes on existing policies, and policy claims. The company serviced the mounting workload with 150 Incoterm terminals that needed to be replaced.
With the three-building complex, the terminals were interconnected by point-to-point cable and multiplexers to terminal processing units. Information was then transmitted over wideband, multiplexed data communication networks to the company's telecommunications center in Philadelphia, and to its mainframe computer site nearby (see Figure 1). In this configuration, each time a terminal was relocated, new wires had to be installed at significant cost.
In December 1983, Colonial Penn expanded its southeast regional office and moved to a single, two-story building in Tampa. Before the move took place, the company evaluated local-area networks (LANs) to simplify and accelerate the handling of southeast regional inquiries and data communications with its Philadelphia telecommunications and computer sites. The LAN sought would allow the use of inexpensive, easy-to-install transmission lines, provide simple and reliable information flow controls, plus have expansion and advancement capabilities. Emphasis was also place on "open" LANs, which, unlike "closed" LANs, don't require that data terminal equipment and software be obtaineed from a single supplier.
Colonial Penn selected the Private Local Area Network (PLANET) provided by Racal-Milgo in Miami. This LAN performs predominately as a transport mechanism for a variety of terminal devices made by different manufacturers but attached by standard interfaces. It offers resource sharing and flexible switching capabilities, which are optimized by the token passing of a software packet that enables total protocol transparency.
There are only four basic physical elements in this LAN: a terminal access point (TAO), a cable access point (CAP), a processor called the Director, and a central-site unit combining TAP and CAP functions that's called High-Density PLANET.
The transmission medium is an inexpensive, readily available twin coaxial calbe ring, which permits distances of up to 300 meters between terminal access points.
The LSI/microprocessor-based TAP serves as an intelligent node that enables data terminals access to the cable. Each TAP will connect to RS-232 or V.24/V.28 devices such as terminals and computer ports. Up to 250 TAPs (500 interfaces) may be connected to a single ring. A CAP is a small device that provides access to the ring by connecting to the coaxial cables and to the TAP digital signals. When not connected to a TAP, the CAP simply passes signals on arund the ring.
The Director, which provides the ring's central intelligence, is an LSI/microprocessor device that performs all the connecting, monitoring and managing functions of the system. It may be installed at any position in the network. It uses a nonvolatile cassette memory cartridge containing six kilobytes of low-power, CMOS RAM memory to duplicate part of its internal memory and provides power failure--safe memory for the system's strategic elements. Any asynchronous ASCII terminal is suitable for the with the Director, as is any serial asynchronous ASCII printer having data rates up to 9600 b/s for log printing functions. Operates at Approximately 10 Mb/s
The LAN operates at approximately 10 Mb/s and accepts any standard terminal, computer or communications device using RS-232 or V.24/V.28 interfaces at speeds up to 19.2 kb/s (synchronously or asynchronously). No amplifiers of physical plant components are needed. Network response times are short and guaranteed, a fact that makes the network suitable for polling systems, process control, digitized voice and a wide variety of other applications.
The ring topology lends itself to many possible future enhancements, such as fiber-optic and broadband links. And because of the network's protocol independence, a mixture of different manufacturers' equipment can co-exist with simultaneous transmissions at differing speeds, protocols and applications. The network provides several features, including security, timeshare queuing, auto-baud, port contention and selection.
A PLANET ring is now installed on each floor of our new Tampa office building. The rings interconnect 200 Honeywell 7311 terminals to the protocol converters. If a terminal is relocated today, the prior necessity of installing new wires at considerable cost is eliminated. The terminal is simply unplugged from one TAP and plugged into another. The LAN also provides our staff with a distributed switch having built-in port contentions (see Figure 2).
Significantly, we've also arranged to give our PBX access to the ring. Automated call distribution routes telephone inquiries to the correct operator and cuts down call times, making much better use of the staff's time and talents. The connection to the PBX allows supervisory staff to monitor and change call routing from the same terminals that access the entire system.
The network application is quite simple. When terminal operators take their telephone inquiries, they must connect to a particular port at the mainframe computer near Philadelphia. The connect command connects the operator to the first availabe port ona protocol converter for further transmission over the telephone lines to the Philadelphia site. There is also a TAP dedicated to a 9600-b/s modem circuit, which allows network managers in Piladelphia to connect to the Director for remote monitoring and administration.
An upgrade in the installation was the replacement of 100 TAPs at the protocol-converter side of the network with High-Density PLANET (see Figure 3). HDP allows for the simplification of cabling and the conservation of rack space. It also provides for a more cost-effective approach and gives us what constitutes a centralized/distributed matrix switch, which allows any network device to connect with any other. This switching capability may be reconfigured electronically, a most-important consideration in view of network design changes or expansions. Minis Are Replacing Converters
In fact, as this article is being written, our company is making significant network changes. It is replacing the protocol-conversion equipment with two local minicomputers (see Figure 4). In this configuration, Honeywell DPS 6s will provide for local processing, remote printing, quicker response times by using X.25 protocol, reduced telephone line costs, and on-site redundancy. This configuration would have proven cost prohibitive with many LANs, but it can be readily accomplished with ours merely by redefining TAP ports.
Another change under way is the addition of tail circuits running to satellite offices in Colonial Penn's southeast region. The first will be in Sarasota, Florida (see Figure 5), where data will be exchanged via low-speed modems. The remote PLANET users will have at their access all of the switching, contention and reconfiguration features available with the main installation. Five additional satellite-office tail circuits are planned for the very near future.
In addition to achieving the goals of inexpensive, easy-to-install transmission media, simple and reliable flow controls, short and guaranteed response times and advancement capabilities, our LAN installation took place with virtually no interruption to on-line systems. We've identified only 20 minutes downtime from the beginning of the initial installation. Uptimes now approach 100 percent.
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|Date:||Dec 1, 1984|
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