Weighted SRLG Path Selection for Network Traffic Protection
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Solution Overview
Problem
Existing Loop-Free Alternate (LFA) path selection implementations in Interior Gateway Protocol (IGP) networks suffer from deficiencies in Shared Risk Link Group (SRLG) protection, as they only consider local links, leading to potential traffic diversion over failed links and lack of flexibility in selecting backup paths.
Innovation Solution
The proposed solution involves determining three shortest path trees: a first shortest path tree based on normal IGP metrics, a second shortest path tree after removing a protected element, and a third shortest path tree which is a weighted version of the second tree, penalizing links sharing the same SRLG value as the protected element. Traffic enforcement is then performed based on a comparison of these trees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If local SRLG protection is implemented considering only directly connected links, then the protection mechanism is simple to implement, but the backup path may still cross failed links sharing the same SRLG value
Solution Approach 1:
The patent transitions from local SRLG protection (considering only directly connected links) to remote SRLG protection (considering all links in the network). This dimensional expansion allows the backup path selection to account for SRLG values of remote links, ensuring that the backup path does not cross failed links sharing the same SRLG value, thereby resolving the contradiction between implementation simplicity and protection effectiveness
Solution Approach 2:
The patent introduces a new parameter dimension by incorporating remote SRLG values into the backup path selection process. By modifying the path selection criteria to include SRLG values of all links (not just local ones), the system achieves more effective SRLG protection while maintaining a relatively simple implementation through existing shortest path tree algorithms
2Productivity
If backup paths are selected without considering remote SRLG values, then the path selection process is computationally simple, but traffic may be diverted over failed links
Solution Approach 1:
The patent performs preliminary computation of shortest path trees with penalized remote SRLG values before actual backup path selection. By pre-calculating the third shortest path tree with SRLG penalties and comparing it with the first shortest path tree, the system identifies valid backup paths that avoid failed links, achieving both computational efficiency and traffic protection reliability
Solution Approach 2:
The patent replaces complex real-time path analysis with a pre-computed comparison approach. Instead of analyzing all possible backup paths in real-time, the system pre-calculates shortest path trees with and without SRLG penalties, then compares them to identify valid backup paths, significantly improving computational efficiency while maintaining protection reliability
3Adaptability or versatility
If all available backup paths are considered without SRLG weighting, then path selection flexibility is high, but the optimal protected path cannot be guaranteed
Solution Approach 1:
The patent introduces SRLG weighting as a new parameter to the path selection process. By assigning penalty values to links based on their SRLG values and computing the third shortest path tree with these weights, the system can prioritize paths that avoid links sharing SRLG values with protected links, ensuring optimal protected path selection while maintaining flexibility through the segment routing architecture
4Reliability
If remote SRLG values are incorporated into backup path selection, then SRLG protection effectiveness is improved, but the computational complexity increases
Solution Approach 1:
The patent performs preliminary computation of shortest path trees with penalized remote SRLG values before actual backup path selection. By pre-calculating the third shortest path tree with SRLG penalties and comparing it with the first shortest path tree, the system identifies valid backup paths that avoid failed links, achieving both computational efficiency and traffic protection reliability
Solution Approach 2:
The patent creates a copy of the network topology (third shortest path tree) with modified SRLG penalty values applied to remote links. This copied structure allows the system to evaluate backup paths with remote SRLG considerations without fundamentally changing the existing path computation infrastructure, thereby managing computational complexity while improving protection effectiveness
Data Source
AI summary
A method includes generating a first shortest path tree for traffic routing in a network, the first shortest path tree identifying a corresponding shortest path from the network node to other nodes in the network and generating a second shortest path tree for traffic routing after removing an element from the network. The second shortest path tree identifies a corresponding shortest path from the network node to the other nodes in the network with the element removed. A third shortest path tree is generated, which is a weighted version of the second shortest path tree with a weight value added to any node or link in the network sharing a SRLG value with the element removed from the network. Network traffic is enforced based on a comparison of the third shortest path tree with at least one of the first shortest path tree and the second shortest path tree.