Essay About Simplification Of Fault Isolation And Traditional Approaches

Communications Magazine
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A Symptom-Driven
Expert System for
Isolating and
Correcting Network
Faults
Todd E. Marques
March 1988-Vol. 26, NO. 3
IEEE Communications Magazine
Introduction
To day a single data network c m c onsist of d o ~ e n s of geographically distributed switching nodes
and concentrators, and can support numerous nichespecific
communications protocols, terminal devices,
and network access facilities. The task of isolating
faults within large and complex networks can be
extremely demanding. Competency in this area requires
a general command of data communications princ iples
and sectionalization strategies, as well as specific
knowledge about the operations and diagnostic capabilities
of a wide variety of network components. The
demands of this task are likely to grow as new and varied
product offerings are deployed, and as the sheer size
and topological complexity of networks increase.
This article discusses recent work geared toward the
simplification of fault isolation within data net+-orks.
Traditional approaches to task simplification have
focused on properties of the user interface. The use of
color, graphics, pan and zoom, and many othcr coding
and display techniques can provide users with the critical
information required to make sound and timely
decisions. Yet the judgment processes, which c Iearly
are among the most difficult aspects of man) tasks,
remain the purview of the user. Thus, i t is not clear
that advanced interface techniques actually reduce the
skill level required to perform complex problem solving
tasks such as fault isolation. The approach
reported in this paper focuses less on the presentation
of key information and more on the interpretation of
key information.
SturKeeper@ Network Troubleshooter is a real-time
interactive expert system that was developed to simplify
the task of fault isolation by mechanizing many of thc key
judgment processes. Based on a symptom description and
situation-specific background data supplied by the user,
Troubleshooter identifies all suspicious components,
formulates a plan designed to minimize the amount of
time taken to isolate the fault, executes the plan, and
terminates after the fault has been isolated and corrected.
The system is designed to be used by individuals
with widely varying skill and experience levels.
As shown in Fis. 1, Troubleshooter is positioned
between a clerk, technician, or administrator staffing a
help desk and a conventional operations system (OS).
Troubleshooter interacts with the OS much like a
human user. It has access to the entire OS command
set as well as all reports and displays available to any
other authoriLed user. Troubleshooter determines which
OS commands should be executed in a given situation,
executes the commands, and interprets OS responses.
System input consists mainly of (i) symptom descriptions
that either are reported to the help desk by network
end-users, or are derived from network-generated messages,
and (ii) specific inquiries about the operational
state of a designated component. System output consists
of (i) a diagnosis that identifies the physical address of
the faulty network component, describes the fault, and
provides evidence upon which the diagnosis is based,
(ii) rrsults of any system-initiated proceduies intended
to clear the fault, and in the event that human intervention
is drcmed neccssary to clcar the fault, (iii) adLice on
the appropriate corrective procedures.
6 0163-6804/88/000S-0006 $01 .OO 0 1988 IEEE
Fzg. 1. TroubleJhooter: An Intrllzgent Front-End to an
Erzstzng 0prratzon.c SyJtfm.
Initial Task Domain
Troubleshooter is currently operational in the Datakit@
Virtual Circuit Switch (VCS) networking environment.
Datakit VCS provides data communication
between host computers and terminals of various types.
Datakit VCS networks may range from a simple star
configuration where hosts and terminals are interconnected
via a single node, to a wide area network consisting
of many nodes linked by digital data service or
high speed fiber