Seamless Multipath Retransmission in Source-Routed Tunnels
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Solution Overview
Problem
Non-storing mode in RPL protocols for Low Power and Lossy Networks (LLNs) lacks a mechanism for backtracking source-routed messages, requiring rerouting at the source when link failures occur, which is inefficient and not seamless.
Innovation Solution
A device, such as a root node, encapsulates and transmits packets with a tunnel header indicating a source route, and upon receiving a destination unreachable message, determines the failed link, recovers the original packet's Hop Limit, and re-transmits it on an alternate source route, ensuring seamless multipath retransmission without visible side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If source-routing is employed in non-storing mode RPL, then routing control is simplified, but rerouting efficiency deteriorates when link failures occur
Solution Approach 1:
The patent performs preliminary actions by having intermediate nodes along the source route buffer incoming packets and prepare alternate paths before link failures occur. When a link failure is detected, these pre-positioned packets can be immediately retransmitted through alternate paths without requiring source node intervention, thus resolving the contradiction between simplified routing control and efficient rerouting.
2Adaptability or versatility
If backtracking mechanism is used in storing mode, then alternate path exploration is enabled, but it cannot be applied to source-routed messages
Solution Approach 1:
The patent introduces intermediate nodes along the source route as mediators that perform backtracking functions. These intermediate nodes buffer packets and explore alternate paths when link failures occur, enabling the backtracking mechanism to work with source-routed messages without requiring changes to the source node or destination node, thus resolving the contradiction between adaptability and device complexity.
3Adaptability or versatility
If rerouting occurs at the source node, then routing flexibility is maintained, but network overhead and latency increase
Solution Approach 1:
The patent performs preliminary actions by having intermediate nodes buffer packets and prepare alternate paths before source node rerouting is needed. This allows rerouting to occur locally at intermediate nodes without requiring source node involvement, thus maintaining routing flexibility while significantly reducing rerouting latency and network overhead.
4Reliability
If seamless error recovery is implemented, then network integrity is maintained, but packet buffering requirements increase
Solution Approach 1:
The patent applies local quality by having only intermediate nodes along source routes perform buffering and error recovery functions, rather than requiring all nodes or the source node to provide these services. This localized approach maintains seamless error recovery capability while minimizing overall packet buffering requirements in the network.
Data Source
AI summary
In one embodiment, a device receives a destination unreachable message originated by a particular node along a first source route, the message carrying an encapsulated packet as received by the particular node. In response, the device may determine a failed link along the first source route based on a tunnel header and the particular node. Once determining an alternate source route without the failed link, the device may re-encapsulate and re-transmit the original packet on an alternate source route with a new tunnel header indicating the alternate source route (e.g., and a new hop limit count for the tunnel header and an adjusted hop limit count in the original packet).