Why three users replaced modems with CO LANs.
Their old network consisted of buffered teletypewriters and leased lines linked at 300 bits per second. They replaced the TTYs with a minicomputer and remote PCs and updated the dedicated network with New York telephone's Intellipath CO LAN service.
Their experience demonstrates how central office data service offers a fast, reliable and economical alternative to low-speed analog modems.
New York Telephone used Northern Telecom's DMS-100 switch and DiaLAN technology to provide 9600 bps CO LAN service to all 14 precincts and headquarters. Each location uses integrated voice and data multiplexers (IVDMs) to connect the personal computers to the network.
Using DiaLAN, the department transmits general orders, missing-person reports, and other electronic messages. Because DiaLAN is a data-over-voice service, the phone lines used for the data network are still available for voice calls.
Buffalo's police department demonstrates the value of a fresh look at central office data services: CO LAN and Switched 56. CO LAN has been around for over five years, but the name is misleading. It implies that CO LAN competes with traditional premises-based LANs, but rarely is the service used in their place.
What CO LAN and CO-based data services in general offer is viable alternative where analog modems have traditionally been used.
What CO data is
CO-based data is switched data communications provided through the telephone company CO. It allows users to exchange data over voice lines at speeds from 300 bits per second to 64 kb/s.
Because the transmission is all digital, the advertised speed is really delivered. The speed degradation common with "high speed" (9.6, 14.4 and 19.2 kb/s) modems is eliminated.
Two CO data services -- Data Over Voice, and Switched 56 -- have been around the longest.
Data Over Voice uses integrated voice and data multiplexers to combine one voice channel and one or two data channels on one standard twisted pair line.
Switched 56 uses digital data units to drive transmission speeds up to 56 kb/s in a non-CCS7 multi-office environment or 64 kb/s in a single office or CCs7-linked multi-office environment.
Both services offer total network administration and maintenance by the phone company.
WLR Foods, the country's eighth largest poultry producer, has 10 locations in Rockingham County, VA. The include feed mills, hatcheries, processing plants, and offices.
To provide communications between nearly 100 remote terminal devices and the company's NCR computer, WLR used analog modems operating at 2400, 4800, and 9600 bits per second, and a combination of dial-up and leased lines.
The company was not a centrex user until Contel of Virginia approached them with the benefits of CO data.
The company is now implementing CO data services to provide a higher speed, lower cost network.
Contel provides Data Over Voice service in lieu of dial-up, analog modems to connect WLR's single terminal sites.
Larger concentrations of users, connected to the mainframe via multiplexers, will be served by Northern Telecom's Datapath 56 kb/s service.
WLR currently connects its Broadway chicken processing facility to its main office at Hinton, 20 miles away, over a 56 kb/s leased line.
The line is shared by three Codex multiplexers serving over 40 terminals and a 19.2 kb/s modem serving a high-speed printer.
The company plans to use four 19.2 Datapath lines to connect these devices to the mainframe.
"By replacing the leased line with Datapath, we'll save around $ 400 per month and provide our users a larger pool of bandwidth at the same time," says Jim Howes, manager of MIS for WLR Foods.
The National Institute of Environmental Health Sciences employs nearly 1000 people in a 20-building campus in Research Triangle Park, N.C. It is home to a successful LAN bridging application of CO data service.
NIEHS is served by CO data from GTE South's nearby CO.
"We've used Switched 56 service to create an extended Ethernet LAN," says Charles Tate, an electronics engineer. "We get reliable, high speed service and we're saving money over a leased line arrangement."
3Com bridges are connected to the Ethernet LAN at each site. The bridges are connected to high speed data units that switch through the public network via DMS-100 Datapath service, providing 56 kb/s LAN bridging for some 200 users.
The applications for CO data services are many and varied. And they're growing.
With inexpensive IVDMs, Data Over Voice can be used instead of dial-up modems. Group IV fax, video conferencing, leased line backup, and disaster recovery are up-and-coming applications for switched 56 service.
How can users get more benefit from CO data? How can telcos sell more of the service?
The answer to both questions is to recognize the breadth of applications possible. Users like the benefits of high performance, all-digital reliability, telco network management, and low cost.
Telcos are reaching out to non-centrex customers.
Perhaps we should stop using the term "COLAN." It's CO data...which means communication with any device, anywhere, anytime.
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|Title Annotation:||central office local area networks, Buffalo Police Department, WLR Foods, National Institute of Environmental Health Sciences|
|Date:||Jun 1, 1991|
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