Network Element Wait-to-Restore Timer for Intermittent Failure Protection

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Solution Overview

Problem

In optical communication networks, intermittent failures on working paths lead to periodic traffic loss due to traditional protection switching configurations that redesignate faulty paths as active, causing repeated protection switches and increased disturbances.

Innovation Solution

Implementing a method where network elements transition to a waiting-to-restore state upon fault clearance, maintaining the protection path active until a timer expires, thereby reducing unnecessary switches and traffic disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional protection switching configuration redesignates working path as active after fault clearance, then path utilization is improved, but traffic loss increases due to intermittent failures

Engineering Contradiction:

Improvepath utilizationVSAvoidtraffic loss

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary action by implementing a wait-to-restore timer before redesignating the working path as active. This timer delays the path transition until after the intermittent failure has fully cleared, preventing premature switching that would cause traffic loss. The timer ensures the working path is stable before becoming active again.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention applies beforehand cushioning by maintaining the protection path as active during the wait-to-restore period. This creates a cushioning effect where the protection path is ready to immediately carry traffic if the working path fails again, preventing traffic loss during the transition period.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If protection switch is implemented for each intermittent failure, then traffic loss is reduced, but protection switch frequency increases causing more disturbances

Engineering Contradiction:

Improvetraffic loss reductionVSAvoidprotection switch frequency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The wait-to-restore timer implements preliminary action by delaying the protection switch back to the working path until the failure condition has fully cleared. This prevents premature switching that would trigger another protection event, thereby reducing the overall frequency of protection switches while still protecting against traffic loss.

Inventive Principle:

Principle #10Preliminary action

3Speed

If working path is immediately restored after fault clearance, then system responsiveness is improved, but intermittent failures cause repeated protection switches

Engineering Contradiction:

Improvesystem responsivenessVSAvoidpath stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9013977B2Method and system for reducing traffic disturbance in a communication network caused by intermittent failure

Publication Date: 2015.04.21 FUJITSU LTD

AI summary

A method may include: (i) in response to clearing of a fault on a working path of a protection switching group to which a first network element is interfaced: (a) transitioning, by the first network element, its state to a first state in which a protection path of the protection switching group is active; and (b) initiating, by the first network element, a wait to restore timer, the wait to restore timer having a duration such that upon expiration of the timer, the first network element is configured to switch the working path to active; and (ii) in response to receiving a message from a second network element interfaced to the protection switching group indicating that a failure has occurred on the working path: (a) maintaining, by the first network element, its state in the first state; and (b) continuing, by the first network element, the wait to restore timer.