Browse Prior Art Database

Hybrid Dual Threshold Algorithm for Managing Link Performance Counters

IP.com Disclosure Number: IPCOM000108506D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 5 page(s) / 229K

Publishing Venue

IBM

Related People

Irvin, DR: AUTHOR [+2]

Abstract

Past and present techniques for managing link-performance data rely on comparing, at certain intervals, the contents of a counter that accumulates transmission errors or some other proxy for degraded transmission quality to a fixed, numerical threshold that marks the minimum acceptable level of performance. When the value of the counter exceeds this threshold, an alert indicating the failure or impending failure of a link component is sent to the network operator, so that the operator may act to remedy whatever cause of degradation is at work. (Image Omitted)

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Hybrid Dual Threshold Algorithm for Managing Link Performance Counters

       Past and present techniques for managing link-performance
data rely on comparing, at certain intervals, the contents of a
counter that accumulates transmission errors or some other proxy for
degraded transmission quality to a fixed, numerical threshold that
marks the minimum acceptable level of performance.  When the value of
the counter exceeds this threshold, an alert indicating the failure
or impending failure of a link component is sent to the network
operator, so that the operator may act to remedy whatever cause of
degradation is at work.

                            (Image Omitted)

      The degradation of a link may arise from an abrupt failure of a
link component or from the gradual deterioration in quality of the
underlying transmission channel.  Gradual deterioration is often
driven by some form of electromagnetic noise, where that noise is
described by a stochastic process.  Stochastic noise, however, is
always present as an interfering component that operates in the
background of transmission channels; consequently, the distinction is
not always clear between a healthy transmission channel that is
experiencing temporary difficulty as the natural result of the random
fluctuations expected of noise, and a troubled channel that is
experiencing the early stages of noise-driven failure.

      The numerical value of the fixed threshold must be chosen so
that the need for sending an alert can be determined under five
different operating conditions:
       .   A healthy channel operating within its nominal bounds of
operation,
       .   A healthy channel temporarily perturbed outside its
nominal bounds of operation by the chance occurrence of noise,
       .   A channel operating in the gray-area of stable but
mediocre performance just below the threshold,
       .   A channel that is driven through stages of degraded
performance toward failure by a systematic increase in the
interfering noise, and
       .   A channel that is in a state of complete failure.

      The desire to pass judgement on these five operating conditions
in the presence of random noise puts conflicting requirements on the
fixed threshold.  If the threshold is set too low, then the normal
noise fluctuations present in the healthy channel will result in the
sending of false alerts, which distract the network operator and
provide incorrect and unneeded information.  If the threshold is set
too high, then states of gray-area performance may not be detected at
all, and states of progressive deterioration that drive toward
failure may be detected only after a considerable delay.  The
invention disclosed here improves the capability of a
network-management application to judge numerical data on link
performance and to decide whether an alert indicating the failure or
impending failure of the link should...