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Marathon Oil ends line rasp.


Dave Hoxworth will always remember the challenge of calling Marathon Oil's research facility in Littleton, Colo., from Lafayette, La., where he was in charge of Marathon's offshore oil rig communications.

"There was so much noise on the line you could hardly hear," says Hoxworth, imitating the grating sound. Three "hops" over the leased line network each added noise. Calls went through Houston; to Findlay, Ohio, Marathon's biggest plant; to Littleton.

The call paths haven't changed, but the network has and the line noise is gone. Marathon installed T1s to link its eight major facilities.

Hoxworth is now in Findlay, where he was part of the team responsible for putting Marathon onto T1s and vastly improving the quality of its voice communications.

"The network has allowed our users to be much more efficient--to be able to hear when you call somebody."

Also, it increased Marathon's flexibility in network configuration, and has provided quality service to some relatively remote locations.

On the network are the Findlay facility and data center; Houston headquarters; Littleton research center; Lafayette, La., and Midland, Texas, production offices; Robinson, Ill., and Detroit refineries; and Springfield, Ohio, EMRO (non-Marathon brands) subsidiary operations headquarters. Numerous other sites are connected to each of those nodes via leased lines, and in some cases microwave or VSATs.

Marathon's network has a mix of about 60% voice, 40% data. Before the T1 upgrade, data was sent over separate lines, so it was not affected by the poor quality of the lines. But the change to T1s greatly increased Marathon's capacity for data.

"Prior to the T1s we essentially had two separate networks," explains Hoxworth. "What really made the thing pay for itself was the ability to pull both of those into the single pipe."

Another T1 network benefit was the establishment of a 112-kb/s connection between Houston and Littleton. The Colorado research facility has a powerful Cray computer used for modeling underground oil reservoirs based on seismic and other data provided by remote facilities.

Big File Transfers

Modeling means transfers of "enormous" data files to and from Littleton.

At Findlay is an IBM 3090 mainframe and an IBM 3725 front-end processor. There is also a 3725 at Houston.

What convinced Marathon to go with T1s was a pilot installation of a T1 between Lafayette and Houston.

At Lafayette, Marathon had what amounted to its own telco, with microwave and two-way radio links to offshore rigs. Once the T1 was in place, when anyone called Houston the line was perfectly quiet. As soon as connections went over the leased lines beyond Houston, the noise returned.

Part of the problem was attributable to TASI (time assignment speech interpolation) equipment around the network. The analog multiplexing gear "basically took 20 lines of traffic and put it on 14 physical lines, by interleaving the conversations. It was a financial success, but quality suffered," he says.

Experience with the Houston-Lafayette T1 "really opened up the doors for using T1 in other locations and ultimately for taking it to network-wide application. We could point not only to the economic advantages of the T1 but the quality advantages," he says.

When Hoxworth was brought to Findlay as telecomm planning analyst, he began work on a network upgrade study. It favored a T1 private network. USX, parent of Marathon, uses the EPSCS (Enhanced Private Switched Communications Service) virtual network.

The savings--$37,600 a month--that T1s offered over EPSCS made the decision clear. But it didn't hurt that AT&T puts its T1 POP across the street from Marathon's Findlay office, in an Ohio Bell central office.

By choosing T1 over virtual networks, Marathon gave up the chance for company-wide seven-digit dialing. Now network users must follow two- or four-digit tandem dialing codes representing calling destinations, plus a four-digit extension number. Those tandem codes vary depending on where a user is located.

Usage of the Marathon network expanded much faster than expected. Hoxworth had projected 20% growth, but says the quality brought onto the network users who had been making off-network calls to company sites previously.

"Now that we have a network they can hear on, most of these calls are made over the network. Unfortunately, the network has filled up to 100% capacity on each loop T1." Spur T1s are still operating at 50% or less.

Marathon's alternatives were adding another T1 between Houston and Findlay, or ADPCM (adaptive differential pulse code modulation) to compress the voice traffic and make more efficient use of the T1 capacity.

Freeing Bandwidth

Marathon is implementing ADPCM around the loop, preferring the one-time equipment charge to the continuing cost of another T1.

"ADPCM will free up bandwidth for some of our upcoming needs. We are in the process of adding locations to the network, which will ultimately increase traffic, and ADPCM will probably keep us going for some time."

Newbridge Networks ADPCM equipment is being installed. Throughout the company, Marathon uses Newbridge T1 gear, including the MainStreet 4602 network management system.

In addition, Marathon plans to add T1 links to incorporate newly merged Texas Oil and Gas offices into the network. Those changes will create a second loop that will ease strain on the rest of the network and provide redundant paths for traffic.

When there is trouble on the network, data traffic is automatically rerouted but voice traffic is not.
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.

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Title Annotation:sixth of seven articles on T1 communications
Author:Tanzillo, Kevin
Publication:Communications News
Date:Oct 1, 1990
Previous Article:T1 backbone cures school growth pains.
Next Article:Voice and data via satellite.

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