Locally-Optimized Tree Bypass in LLN RPL Topologies

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Solution Overview

Problem

Existing tree-based topologies in Low-Power and Lossy Networks (LLNs) face inefficiencies in implementing bypass paths that optimize data packet forwarding, particularly in large-scale DODAGs with thousands of RPL nodes, due to processing burdens on the DAG root and limited routing information, leading to sub-optimal paths and scalability issues.

Innovation Solution

A method where a destination network device initiates the generation of a locally-optimized tree within the existing tree-based topology by propagating confined advertisements, allowing local RPL nodes to determine their own optimizations and join the tree, thereby bypassing the root device and optimizing data packet forwarding without centralized calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If centralized path calculation is implemented at the DAG root to optimize P2P routing, then routing optimization is achieved, but processing burden on the root device increases and scalability is limited

Engineering Contradiction:

Improverouting optimizationVSAvoidprocessing burden on root device

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the centralized routing optimization problem into localized segments by enabling intermediate RPL nodes to independently calculate and install P2P bypass paths within their own sub-DAGs. This segmentation distributes the processing burden from the root device to local nodes, allowing each node to handle only its relevant routing optimization tasks while maintaining overall network optimization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements local quality by allowing each RPL node to independently perform routing optimization for its own sub-DAG based on locally available topology information. Instead of requiring centralized root device processing for all P2P paths, each node optimizes routing quality locally by calculating bypass paths through its children and grandchildren nodes, reducing the root device's processing burden while maintaining routing optimization.

Inventive Principle:

Principle #3Local quality

2Productivity

If bypass paths are implemented to optimize P2P routing, then routing efficiency improves, but processing burden on the DAG root increases

Engineering Contradiction:

Improverouting efficiencyVSAvoidprocessing burden on root device

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies self-service by enabling RPL nodes to autonomously calculate and install P2P bypass paths within their sub-DAGs without requiring centralized root device intervention. Each node independently performs routing optimization by examining its local topology information, calculating optimal bypass paths through its descendants, and installing routing tables locally, thereby improving routing efficiency while eliminating the processing burden on the root device.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent implements preliminary action by having RPL nodes pre-calculate and install P2P bypass paths within their sub-DAGs before actual data transmission occurs. Nodes proactively examine their local topology, identify potential bypass paths through children and grandchildren nodes, and prepare routing tables in advance, enabling efficient P2P routing without requiring real-time root device processing.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If localized optimization is implemented at each RPL node, then scalability improves and processing burden is distributed, but routing information availability is limited

Engineering Contradiction:

ImprovescalabilityVSAvoidrouting information availability

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The patent applies partial action by having each RPL node perform routing optimization only for its own sub-DAG using locally available topology information from DIO messages. Nodes don't need complete global network information to effectively optimize P2P paths within their local scope, as most P2P traffic occurs within or near their sub-DAG. This partial optimization approach enables scalability while working within the constraints of limited local routing information.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10938707B2Peer-to-peer optimization in existing tree-based topology based on generating locally-optimized tree using confined advertisements

Publication Date: 2021.03.02 CISCO TECHNOLOGY INC

AI summary

In one embodiment, a method comprises determining, by a network device, a hop-by-hop path in a low-power and lossy network having a tree-based topology originated at a root network device, the hop-by-hop path comprising identified network devices for forwarding a data packet from a source network device to a destination device in the tree-based topology; and causing, by the network device, the destination device to initiate generation of a locally-optimized tree that bypasses the root network device and optimizes forwarding of the data packet from the source network device to the destination device, based on confined advertisements within the tree-based topology relative to the identified network devices.