LFA Selection Control via Local Tagging and Weighting
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Solution Overview
Problem
Existing IGP protocols face limitations in selecting the desired alternative path for Loop Free Alternatives (LFA) due to lack of control over LFA selection, requiring changes to the IGP protocol that may not be feasible in all implementations.
Innovation Solution
A method and system that allow administrators to override the LFA selection process using a local tagging mechanism, enabling control over LFA selection for a given destination node by using a tag and weight, without requiring enhancements to the IGP protocol, by selecting a next candidate node from neighbor nodes, checking for tag matching, and replacing stored LFA with the preferred node based on weight comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If existing provisioning software is used to control LFA selection, then some control over LFA provisioning options is enabled, but the desired alternative path cannot always be selected and IGP protocol changes may be required
Solution Approach 1:
The patent introduces a local tag as an intermediary mechanism that sits between the existing IGP protocol and the LFA selection process. This tag, stored in the local routing information base, acts as a mediator that guides LFA computation without requiring modifications to the IGP protocol itself, thereby enabling fine-grained control while avoiding protocol complexity
Solution Approach 2:
The patent changes the parameter space of LFA selection by introducing configurable tags and weights that can be set by operators. These parameters (tag values and weights) allow flexible control over which LFAs are preferred without altering the underlying IGP protocol behavior, enabling precise control through parameter adjustment rather than structural protocol changes
2Reliability
If RFC 5286 LFA computation is used, then the best protection possible is provided for any destination, but operators cannot override the selection process to choose specific alternative paths
Solution Approach 1:
The patent makes the LFA selection dynamic by allowing operators to configure tags and weights that can change the preferred path based on operational requirements. The LFA computation remains adaptable by considering both the automatic best-protection criteria from RFC 5286 and the operator-defined preferences through tag matching, enabling the system to dynamically adjust between automatic optimization and manual control
Solution Approach 2:
The patent implements a feedback mechanism where operator-configured tags and weights influence the LFA selection process. The LFA computation feedback loop now incorporates operator preferences through tag matching, allowing the system to adjust its path selection based on both automatic protection metrics and operator-defined requirements, creating a closed-loop control system
3Ease of operation
If existing provisioning software is used, then LFA provisioning options can be controlled, but changes to the IGP protocol may be required which are not feasible in all implementations
Solution Approach 1:
The patent segments the LFA control functionality into a separate, independent layer that operates alongside the IGP protocol without requiring integration into the protocol itself. By placing tag configuration and LFA computation control in the routing information base and LFA computation module respectively, the solution separates concerns and allows provisioning control to be implemented independently of IGP protocol modifications
Solution Approach 2:
The patent enables the LFA computation process to self-adjust based on locally stored tags and weights without requiring external protocol changes or complex provisioning software. The network device uses its own local routing information base and LFA computation logic to automatically select preferred LFAs based on operator-configured parameters, making the system self-sufficient and avoiding the need for external protocol enhancements
Data Source
AI summary
The method and system to computes an LFA next hop as a backup for a primary path next hop that enables an administrator to control LFA selection for a given destination node using a tag and a weight. The method includes checking whether an interface of a next candidate node has a tag with a tag value matching a tag value of a primary SPF path for the destination node. The method further includes checking whether the destination node has any LFA, checking whether a stored tag differs from the tag value of the primary SPF path, and checking whether the interface of the next candidate node is preferred based on a comparison of a weight values, and replacing a stored LFA for the destination node with the next candidate node. Where conditions are met a stored LFA is replaced with the next candidate node.