MPLS Fast Reroute Bypass Tunnel Path Flow Formulation
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Solution Overview
Problem
Existing Fast Reroute (FRR) mechanisms in MPLS networks face challenges in efficiently defining bypass paths that meet various network constraints, such as Quality of Service guarantees and resource limitations, due to the computational complexity of arc-flow formulations.
Innovation Solution
A path-flow formulation is introduced to identify candidate bypass LSPs that meet specific constraints, followed by an optimization step using linear or integer linear programming to select bypass LSPs, allowing for user-selectable non-linear constraints and reducing computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If arc-flow formulation is used to define FRR bypass LSPs, then bypass paths can be established, but computational complexity increases and ability to accommodate network constraints is limited
Solution Approach 1:
The patent transforms the bypass LSP definition problem from an arc-flow formulation to a path-flow formulation, changing the mathematical parameters and variables used in the optimization model. This parameter change enables the problem to be expressed as a linear programming problem with flow variables on paths rather than arcs, reducing computational complexity while maintaining the ability to define bypass LSPs that satisfy network constraints
2Ease of manufacture
If arc-flow formulation is used to define FRR bypass LSPs, then bypass paths can be established, but ability to accommodate network constraints is limited
Solution Approach 1:
By changing from arc-flow to path-flow formulation, the patent enables the incorporation of user-selectable non-linear constraints (such as hop limits, diversity constraints, and shared risk group constraints) directly into the linear programming model. The path-flow variables allow these constraints to be expressed as linear inequalities, significantly improving the adaptability of the bypass LSP definition process to various network requirements
3Reliability
If spare link subscribed bandwidth is allocated to bypass LSPs, then network survivability is improved, but link spare subscription increases
Solution Approach 1:
The patent merges the bandwidth allocation decisions for multiple bypass LSPs into a unified linear programming optimization problem. By combining the constraints and objectives for all bypass LSPs simultaneously, the model identifies opportunities to share spare link capacity across different bypass paths, reducing the total link spare subscription required while maintaining network survivability through diverse protection paths
4Productivity
If optimization step is performed to select bypass LSPs, then bandwidth allocation is optimized, but computational processing time increases
Solution Approach 1:
The patent extracts the bypass LSP selection and bandwidth allocation problem from the complex arc-flow formulation and formulates it as a standalone linear programming problem with clearly defined variables, constraints, and an objective function. This extraction allows the use of efficient LP solution algorithms that can quickly compute optimal bandwidth allocations even for large networks, reducing computational processing time while maintaining optimization quality
Data Source
AI summary
A path-flow formulation of defining MPLS FRR bypass LSPs is presented. The path-flow formulation comprises first identifying a set of candidate bypass LSPs, each of which meets various network constraints and has an explicit route around a network facility to be protected. The constraints may include Quality of Service (QoS) guarantees, implementation requirements, network element resource limitations, and resiliency requirements. The constraints may be user-selected, and may be non-linear. The set of candidate bypass LSPs form a linear programming (LP) problem, or an integer linear programming (ILP) problem if the allowable number of bypass LSPs is constrained. In an optimization step, LP solutions are used to select the bypass LSPs from among the candidate bypass LSPs by allocating bandwidth to them.