Segment Routing K-Shortest Paths with MSD-Aware Yen Enumeration
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Solution Overview
Problem
Segment Routing networks face issues with Maximum Segment Depth (MSD) constraints, where the shortest path calculated by conventional CSPF algorithms cannot be encoded in an acceptable number of segments, rendering it useless for deployment.
Innovation Solution
Implement a modified Yen's algorithm that enumerates multiple CSPF paths, considering MSD constraints, to find k-shortest paths that satisfy the MSD requirement, using pruning criteria to exclude paths that exceed the MSD limit and optimize path exploration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional CSPF algorithm is used to compute the shortest path, then the path length is minimized, but the number of segments exceeds the Maximum Segment Depth (MSD) constraint making the path unusable
Solution Approach 1:
The patent applies dynamics by making the path computation process adaptive and iterative. Instead of a static single-path CSPF algorithm, the system dynamically adjusts by enumerating multiple paths (k-shortest paths) and adaptively selecting those that satisfy MSD constraints. The algorithm evolves from computing one shortest path to computing multiple candidate paths and selecting valid ones based on segment depth criteria.
Solution Approach 2:
The patent changes the parameter of path enumeration from k=1 (single shortest path) to k>1 (multiple paths). By modifying the path computation to generate and evaluate multiple candidate paths with different segment depths, the system can select paths that satisfy MSD constraints while maintaining reasonable length. This parameter change transforms the problem from finding one optimal path to finding multiple acceptable paths.
2Reliability
If multiple CSPF paths are enumerated to satisfy MSD constraint, then MSD compliance is improved, but the computational complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the k-shortest paths before selecting the final valid path. Instead of computing paths on-demand during route selection, the system proactively generates multiple candidate paths in advance, filters them against MSD constraints, and prepares a sorted list of valid options. This preliminary computation separates the path enumeration task from the path selection task, improving overall efficiency.
Solution Approach 2:
The patent extracts the path enumeration and validation functions as separate, independent components. The k-shortest path computation is extracted as a distinct step that produces candidate paths, which are then independently filtered and validated against MSD constraints. This extraction allows the system to reuse the same enumeration logic for different MSD values and network conditions without recomputing everything.
3Adaptability or versatility
If k-shortest paths algorithm is implemented, then viable path options meeting MSD constraints are provided, but the algorithm complexity increases compared to standard CSPF
Solution Approach 1:
The patent applies segmentation by dividing the path computation process into distinct phases: (1) enumerate k candidate paths using modified Yen's algorithm, (2) validate each path against MSD constraints, (3) sort and select valid paths. This segmentation of the computation process into modular steps makes the complex k-shortest path algorithm more manageable and maintainable, while also allowing for optimized implementation of each individual phase.
Data Source
AI summary
Systems and methods for k-shortest paths computation in Segment Routing considering segment depth include receiving a request for a path in a Segment Routing network from a first node to a second node with the path having a pruning criteria; determining a shortest path utilizing a Constrained Shortest Path First (CSPF) algorithm with a sorting criteria used as a metric in the CSPF algorithm; utilizing a modified Yen's algorithm to determine one or more additional paths based on diversions from the shortest path, wherein the modified Yen's algorithm explores the diversions based on the pruning criteria; and providing the shortest path and the one or more additional paths as a response to the request, each of the shortest path and the one or more additional paths pass the pruning criteria.