Segment Routing Adjacency Segment Node Protection
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Solution Overview
Problem
Existing segment routing technologies face challenges in providing fast reroute protection against node failures when the active segment is an adjacency segment, as current methods primarily focus on protecting node segments rather than adjacency segments.
Innovation Solution
The solution involves extending Interior Gateway Protocol (IGP) messages to carry information about node protection for adjacency segments, allowing a path computation engine or segment routing tunnel head-end to select strict paths that include protected adjacency and node segments, and enabling any node to act as a point of local repair to pre-compute and pre-program backup paths for downstream node failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If segment routing is used to provide fast reroute protection, then reliability against node failures is improved, but device complexity increases due to the need for path computation engines and extended IGP messages
Solution Approach 1:
The patent implements pre-computation of backup paths and pre-programming of reroute information in IGP messages before failures occur. Path computation engines calculate alternative paths in advance and store them at network nodes, enabling immediate switching to backup paths when failures are detected, thus improving reliability while managing complexity through advance preparation
Solution Approach 2:
The patent introduces path computation engines as intermediary components that separate the complex path computation function from regular network nodes. These specialized entities handle the sophisticated calculations and algorithms needed for failure protection, allowing standard nodes to simply execute pre-computed rerouting decisions, thereby distributing complexity appropriately
2Speed
If backup paths are pre-computed and pre-programmed, then rerouting speed is improved during failures, but loss of time occurs during the setup phase for computing and distributing backup path information
Solution Approach 1:
Backup paths are computed and distributed in advance during normal operation when network traffic is stable and computation resources are available. This preliminary setup phase occurs before failures happen, so the time investment is made during low-stress periods, enabling instant rerouting when needed without adding delay to failure response
Solution Approach 2:
The path computation process operates continuously in the background during normal network operation, maintaining updated backup paths as network topology changes. This continuous operation ensures that backup paths are always current without requiring separate computation cycles, thereby minimizing the time penalty while maintaining readiness for immediate rerouting
3Ease of operation
If extended IGP messages are used to carry adjacency segment protection information, then ease of operation is improved for network management, but device complexity increases due to message processing requirements
Solution Approach 1:
The patent extends existing IGP message structures to carry multiple types of information including adjacency segment identifiers, backup path information, and protection flags within standardized message formats. This multi-functionality allows a single message type to handle various protection scenarios, reducing the need for multiple specialized message types and simplifying overall message processing despite the increased information content
Solution Approach 2:
The patent modifies IGP message parameters to include optional fields for adjacency segment protection information. These parameters can be selectively included or excluded based on network configuration and protection requirements, allowing nodes to process only the necessary information for their specific role, thereby managing complexity through selective parameter processing
Data Source
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AI summary
In one embodiment, a device in a segment routed network identifies an adjacency segment between the device and another device in the network. The device also identifies a merge point in the network. A first network path extends between the device and the merge point via the adjacency segment. A bypass network path that does not include the adjacency segment also extends between the device and the merge point. The device generates an interior gateway protocol (IGP) message that identifies the adjacency segment and the merge point. The device provides the IGP message to one or more other devices in the network.