LLN Border Router Hot Standby Using a Virtual DODAG Root
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Solution Overview
Problem
Low-power and lossy networks (LLNs) face communication and memory bottlenecks at the LLN Border Router (LBR), which can lead to network instability due to frequent failures, and existing detection methods only address LBR crashes without handling degraded functionality or providing efficient fallback mechanisms.
Innovation Solution
Implement a virtual DODAG root with sentinel nodes that monitor LBR functionality and perform load balancing, allowing for hot standby and fallback without disbanding the DODAG, using consensus-based detection to elect a new LBR when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single LBR is used to represent the bottleneck in an LLN network, then the network structure is simple and easy to manage, but the network stability deteriorates due to frequent LBR failures and lack of fallback mechanisms
Solution Approach 1:
The patent implements hot standby LBRs that are pre-configured and ready to take over if the active LBR fails. This preliminary preparation of backup routers eliminates the need for complex reformation procedures when failures occur, thus improving reliability without significantly increasing network complexity
Solution Approach 2:
The patent changes the operational state parameters of LBRs by introducing different roles (active, standby, candidate) and states. This allows the system to dynamically adjust the functionality and participation level of each LBR, improving network stability through state-based failover while maintaining manageable complexity
2Device complexity
If existing detection methods are used to detect LBR crashes, then the detection process is simple, but the detection capability is insufficient as it does not address degraded functionality or provide efficient fallback mechanisms
Solution Approach 1:
The patent implements a feedback mechanism where sentinel nodes continuously monitor the active LBR's functionality by analyzing DODAG information objects. This continuous feedback loop enables detection of both complete crashes and degraded functionality, improving detection capability while maintaining relatively simple detection procedures
Solution Approach 2:
The patent introduces sentinel nodes as intermediary elements between the active LBR and the rest of the network. These sentinels perform the detection function, separating the monitoring task from other network operations and enabling more sophisticated detection capabilities without complicating the overall system architecture
3Reliability
If the DODAG is disbanded and reformed when LBR failure occurs, then a new LBR can be selected, but the network experiences disruption and the reformation process is complex and time-consuming
Solution Approach 1:
The patent pre-configures hot standby LBRs with all necessary routing information and DODAG parameters before failures occur. This preliminary preparation allows immediate takeover without requiring time-consuming reformation procedures, thus reducing loss of time while ensuring reliable fallback capability
Solution Approach 2:
The patent creates copy instances of the DODAG structure and routing information in the standby LBRs. These copies are maintained in real-time or near-real-time, allowing the standby to immediately assume the active role without needing to reconstruct the DODAG, thereby eliminating reformation time while maintaining fallback reliability
4Productivity
If the active LBR stores per-node state information for each node in the LLN, then routing decisions can be made efficiently, but the LBR becomes a memory bottleneck
Solution Approach 1:
The patent segments the memory storage function by distributing per-node state information across multiple LBRs (active and standby). Each LBR maintains a portion of the routing information, eliminating the single-point memory bottleneck while preserving efficient local routing decision-making capability
Solution Approach 2:
The patent introduces sentinel nodes as intermediaries that assist in maintaining and managing routing information. These sentinels can store and forward routing data, reducing the memory burden on the active LBR while maintaining efficient routing decisions through coordinated information access
Data Source
AI summary
A process can include determining respective link state information corresponding to a plurality of links between two or more border routers and a plurality of child nodes of the two or more border routers, the border routers and the child nodes included in a Destination Oriented Directed Acyclic Graph (DODAG) of a Low-Power Lossy Network (LLN). Consensus information indicative of a current status of each border router of the two or more border routers can be determined based on the respective link state information. The consensus information can be used to update an election of one or more active border routers from the two or more border routers to utilize as a virtual DODAG root for the LLN. Traffic directed to the virtual DODAG root can be routed to an active border router of the two or more border routers based on the updated election.