Modified No-Path DAO Signaling for LLN Route Invalidation
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Solution Overview
Problem
Existing No-Path DAO signaling mechanisms in Low-Power and Lossy Networks (LLNs) are inefficient, leading to stale routing entries, increased control overhead, and reduced success probability due to asynchronous operations and reliance on outdated network information, particularly when nodes switch parents.
Innovation Solution
Implementing modified No-Path DAO signaling where a common ancestor node generates the NPDAO based on mismatch detection and refreshed DAO messages from alternate paths, ensuring NPDAO traverses downstream along the previous path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target node sends NPDAO upstream via its current parent to invalidate the routing path, then the routing path can be invalidated, but the NPDAO message may be lost if the link to the current parent is broken or the parent node has failed
Solution Approach 1:
The patent introduces an intermediary mechanism where the common ancestor node acts as a mediator to detect parent switching and generate NPDAO messages. Instead of relying on the target node to send NPDAO through potentially broken links, the common ancestor node monitors DAO messages and autonomously generates NPDAO when it detects a parent switch, thereby mediating the route invalidation process and improving reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the common ancestor node monitors incoming DAO messages to detect changes in the target node's parent. By continuously observing the routing information and comparing it with stored state, the system can detect parent switches and trigger appropriate NPDAO generation, creating a closed-loop feedback system that improves route invalidation reliability.
2Reliability
If NPDAO is sent upstream to invalidate routes, then routing paths can be invalidated, but the process is asynchronous and relies on outdated network information
Solution Approach 1:
The patent applies preliminary action by having the common ancestor node proactively monitor DAO messages and detect parent switches before the target node attempts to send NPDAO. By detecting the parent switch early through observed DAO message changes, the system can initiate route invalidation immediately, eliminating the asynchronous delay and reliance on outdated information.
Solution Approach 2:
The continuous monitoring of DAO messages by the common ancestor node creates a real-time feedback loop that provides up-to-date network information. This feedback mechanism ensures that route invalidation decisions are based on current network state rather than outdated information, improving both accuracy and timeliness.
3Loss of information
If routing entries are maintained for all nodes in LLNs, then complete routing information is available, but memory resources are consumed on resource-constrained nodes
Solution Approach 1:
The patent extracts the route invalidation function from the resource-constrained target node and relocates it to the common ancestor node which has more resources. By having the common ancestor node generate and propagate NPDAO messages, the system removes the burden of maintaining complete routing information and performing route invalidation from memory-constrained nodes, thereby reducing their memory consumption while preserving routing information completeness through the ancestor's capabilities.
Data Source
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AI summary
Apparatus and method for optimized route invalidation using modified no-path DAO signaling are disclosed. According to the present invention, a node switching its current parent is adapted to send a regular Destination Oriented Directed Acyclic Graph (DODAG) Advertisement Object (DAO) message. Using the changed signaling, the common ancestor node generates an NPDAO on behalf of the switching node on receiving a refreshed DAO from an alternate path. The common ancestor node according to the present invention reuses a same PathSequence from the regular DAO based on which the NPDAO gets generated. The common ancestor node detects routing anomaly using next hop mismatch on reception of the DAO to generate the NPDAO on behalf of the target node. The No-Path DAO traverses downward/downstream along the previous path, unlike any other DAO messages traverses upstream according to convention approaches. The present invention provides a new signaling mechanism for route invalidation in constrained networks.