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Browse Prior Art Database

Selection of Optimal Speed for Modem Operation During Degraded Conditions

IP.com Disclosure Number: IPCOM000089513D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Moore, R: AUTHOR

Abstract

This article describes a technique to enable the selection of full speed or half speed to maximize throughput in a modem network in degraded conditions.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

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Selection of Optimal Speed for Modem Operation During Degraded Conditions

This article describes a technique to enable the selection of full speed or half speed to maximize throughput in a modem network in degraded conditions.

At present, in 4-wire multidrop modem networks, facilities exist that test whether the lines and/or modems leading to terminals are "go" or "no go". This information is not sufficient, however, to determine the degradation suffered by a modem network or whether it is still worthwhile trying to use the modem network.

A notion of "value" that is to be annexed to each terminal and, through it, to its attached modem is introduced. This "value" is defined as the degradation percentage in the modem network operation if a terminal is nonaccessible.

The allotment of "value" to a terminal is judgmental by the customer, or the result of experience in this type of application, or allocation by terminal type, or by any other valid means.

Consider a typical insurance office installation in town which uses a distributed computer in a nearby town which also is the head office of The insurance group. Such an installation could comprise: - 6 communication terminals (one of which is also the control terminal), - 1 medium-speed printer, and - 1 card reader/punch.

The communication terminals are chiefly used for inputting data to the data base in the remote computer. The printer is used for printing policies and patent notices as well as paychecks, etc. The card reader/ punch is used for loading applications and files, for modifications and for maintaining a hard file in the insurance office.

Now consider the following possibilities: 1. A communication terminal fails. 2. The control communication terminal fails. 3. The card reader/punch fails. 4. The printer fails.

What are the effective degradations in modem network performance as a result of each type of failure? 1. The customer's input capability drops by 20%, or, stated another way, the input operation may take 20% longer to do. But the operation is not stopped. The value equals .20. 2. The customer's input capability is affected by, say, half the previous figure, but the control capability of his installation is lost. He can continue the same function but cannot change it or stop it. The customer may evaluate this failure at 50%. The value is 0.50. 3. The customer no longer has the capability of leading or modifying the remote data base at speed, nor does he have the capability to dump the remote data base on c...