Adaptive Route Reoptimization for Unstable LLN Topologies

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Solution Overview

Problem

In Low Power and Lossy Networks (LLNs), nodes only maintain links in the upward direction and detect link failures reactively, leading to continued traffic being sent down invalid paths when no data packets are sent, as they do not proactively notify the root of link failures in the downward direction.

Innovation Solution

Adaptive route reoptimization is triggered based on network stability metrics, with the frequency of reoptimization inversely corresponding to stability, allowing proactive route repairs and maintaining network reliability by adjusting the rate and scope of route optimizations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If reactive link failure detection is used in LLNs, then resource consumption is reduced, but link validity in downward direction cannot be ensured

Engineering Contradiction:

Improveresource consumptionVSAvoidlink validity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by proactively triggering route reoptimization based on network stability metrics before link failures occur. The root node monitors stability metrics and initiates route reoptimization proactively, rather than waiting for reactive failure detection. This ensures downward link validity is maintained while avoiding continuous proactive keepalive mechanisms that would consume excessive resources.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by making the route reoptimization frequency adaptive rather than fixed. The reoptimization frequency adjusts dynamically based on observed network stability metrics - increasing when instability is detected and decreasing when the network is stable. This dynamic approach balances resource consumption with reliability, solving the contradiction between reactive detection limitations and resource constraints.

Inventive Principle:

Principle #15Dynamics

2Reliability

If proactive route reoptimization is performed frequently, then network reliability is improved, but control overhead increases

Engineering Contradiction:

Improvenetwork reliabilityVSAvoidcontrol overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses dynamics by implementing adaptive reoptimization frequency based on network stability metrics. Instead of frequent fixed-interval reoptimization, the system monitors stability metrics and adjusts reoptimization frequency dynamically - performing reoptimization more often when instability is detected and less often when the network is stable. This reduces control overhead while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies feedback by using network stability metrics to inform route reoptimization decisions. The root node monitors stability metrics (such as link quality, packet loss rates, or routing changes) and uses this feedback to determine when proactive reoptimization is necessary. This feedback mechanism ensures reoptimization occurs reliably when needed while avoiding unnecessary control traffic during stable periods.

Inventive Principle:

Principle #23Feedback

3Quantity of substance

If nodes maintain upward links only, then resource usage is minimized, but downward path validity cannot be detected

Engineering Contradiction:

Improvelink maintenance resourcesVSAvoidlink failure detection

Core Design Contradiction:

Quantity of substanceVSLoss of information

Solution Approach 1:

The patent applies preliminary action by proactively triggering route reoptimization before downward link failures occur. Instead of relying on nodes to maintain downward links or detect failures reactively, the root node proactively initiates route reoptimization based on stability metrics, ensuring downward path validity is maintained without requiring nodes to expend resources maintaining upward-only links continuously.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary approach by introducing network stability metrics as a mediator between link maintenance and failure detection. Rather than requiring direct bidirectional link maintenance or reactive failure detection, the stability metrics serve as an intermediary indicator that triggers proactive reoptimization, indirectly ensuring downward path validity without increasing direct link maintenance resources.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9277482B2Adaptive reoptimization rate for unstable network topologies

Publication Date: 2016.03.01 CISCO TECHNOLOGY INC

AI summary

In one embodiment, the network stability of a communication network is determined based on one or more network metrics related to stability, and then based on the network stability, a particular frequency at which to perform route reoptimization is determined, where the frequency inversely corresponds to the network stability. As such, distributed route reoptimization is triggered in the communication network at the adaptively determined frequency.