Congruent Bidirectional Segment Routing Tunnels for Path Consistency
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Solution Overview
Problem
Segment Routing (SR) tunnels are inherently unidirectional, lacking congruency between forward and reverse paths, leading to issues such as propagation delay and tunnel faults, particularly impacting real-time communication services like voice and video.
Innovation Solution
Implementing congruent bidirectional SR tunnels by modifying Segment Identifier (SID) configurations at source nodes to ensure forward and reverse traffic directions follow the same path, using a deterministic approach with master/slave logic and recursive Equal Cost Multi-Path (ECMP) selection to guarantee path congruency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional unidirectional SR tunnels are used, then path selection flexibility is improved, but propagation delay consistency and fault tolerance deteriorate
Solution Approach 1:
The patent applies asymmetry by introducing direction-aware path selection where forward and reverse tunnels can independently choose paths based on asymmetric metrics. The system allows different path selection behaviors for different directions while maintaining the ability to achieve congruency when needed, resolving the contradiction between flexibility and consistency.
Solution Approach 2:
The patent implements dynamic path selection where the routing decision can change based on the communication direction and current network conditions. The system dynamically adjusts whether to use congruent or independent paths based on service requirements, enabling both flexibility and consistency as needed.
2Ease of manufacture
If conventional unidirectional SR tunnels are used, then implementation simplicity is improved, but fault tolerance deteriorates
Solution Approach 1:
The patent segments the bidirectional tunnel into two independent unidirectional tunnels that can be configured separately. This segmentation maintains implementation simplicity while enabling independent fault management and tolerance mechanisms for each direction, resolving the contradiction between simplicity and fault tolerance.
Solution Approach 2:
The patent implements beforehand cushioning by pre-configuring fallback paths and redundancy mechanisms in case of tunnel failures. The system prepares alternative routing options in advance, ensuring continuous operation during faults without complicating the basic tunnel setup.
3Reliability
If congruent bidirectional SR tunnels are implemented, then propagation delay consistency is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the path selection metrics and SID configuration parameters to achieve congruency. The system changes routing parameters such as cost metrics, next-hop selection criteria, and SID assignment to ensure consistent paths in both directions, resolving the contradiction between consistency and complexity.
Data Source
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AI summary
Systems and methods provide congruent bidirectional Segment Routing (SR) tunnels, namely congruent and fate-shared traffic forwarding for bidirectional SR tunnels. A bidirectional SR tunnel, as described herein, includes two unidirectional SR tunnels where the forward and reverse traffic directions follow the same path through the network when forwarded based on prefix and adjacency Segment Identifiers (SIDs). The term "congruent" is used herein to refer to the fact that the two unidirectional SR tunnels, i.e., the forward and reverse traffic directions, follow the same path through the network but in opposite directions. The guarantee of congruency is based on modification of the Segment Identifier (SID) configuration at the source nodes of each tunnel. Accordingly, the present disclosure maintains compatibility with existing Segment Routing configurations with the modifications solely at the source nodes.