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Browse Prior Art Database

Two Stage Method for Managing Link Performance Counters

IP.com Disclosure Number: IPCOM000110533D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 5 page(s) / 226K

Publishing Venue

IBM

Related People

Irvin, DR: AUTHOR

Abstract

The method described here provides an improved way to detect the onset of degradation in the transmission integrity of a digital communication link. Earlier algorithms having this purpose are variations on one central theme: in these older systems, a count of transmission errors is kept over a short interval of time and compared to a numerical threshold on the expiration of that interval. The result of this comparison is then used when appropriate to trigger an alert that indicates unacceptable transmission integrity. These older tests necessarily suffer as a result of the forced trade between their sensitivity to detect degradation and their propensity to dispatch false alerts.

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Two Stage Method for Managing Link Performance Counters

       The method described here provides an improved way to
detect the onset of degradation in the transmission integrity of a
digital communication link.  Earlier algorithms having this purpose
are variations on one central theme: in these older systems, a count
of transmission errors is kept over a short interval of time and
compared to a numerical threshold on the expiration of that interval.
The result of this comparison is then used when appropriate to
trigger an alert that indicates unacceptable transmission integrity.
These older tests necessarily suffer as a result of the forced trade
between their sensitivity to detect degradation and their propensity
to dispatch false alerts.

      To alleviate the problems that result from this forced trade,
we propose an improved method for managing link performance counters.
The new method has two stages.  One stage compares in the traditional
way a numerical threshold and the count of errored seconds kept over
a short interval of time.  This short-interval stage holds its
traditional role in the method described here, which is to detect
catastrophic changes in transmission integrity.  The other stage
serves as a post-processor that accumulates and transforms data
gathered over a long interval of time from the repeated operation of
the first stage, and compares the resulting composite indicator to a
second numerical threshold.  The purpose of this long-interval stage
is to detect the onset of subtle long-term transmission impairments.

      The short-interval stage of the method described here
incorporates a known algorithm taken from the prior art; such a
short-interval algorithm is integrated into the new two-stage method,
as shown in Figs. 1 and 2.  This particular short-interval algorithm
is shown only for illustration; other embodiments of the two-stage
method described here may incorporate improved versions of the
short-interval algorithm such as the one given in [*].  Beyond this
generic short-interval algorithm, however, two new ideas are proposed
that are not drawn from the prior art, encompassing link-performance
management: (1) the specific operation of the long-interval stage of
the two-stage method, and (2) the coupling of two stages to monitor
the performance of a digital transmission link, where one stage
serves as a post-processor operating on data gathered by the repeated
operation of the other.

      The two-stage method of managing link-performance counters
described below offers three improvements over earlier
performance-monitoring algorithms:
1.  The new method is more sensitive to detecting subtle long-term
degradations in transmission integrity.
2.  The new method can distinguish transient channel impairments from
long-term channel impairments.
3.  The new method offers the option of adjusting its two thresholds
in new ways to suit the user's preference for trading sensitivity
against t...