SR-TE Path FRR Extension After IGP Convergence
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Solution Overview
Problem
Existing solutions for fast re-route protection of Segment Routing Traffic Engineering (SR-TE) paths fail to effectively continue traffic forwarding after the Interior Gateway Protocol (IGP) converges on a transit node failure, leading to dropped traffic due to deleted forwarding entries.
Innovation Solution
Implement methods and protocols to extend fast re-route protection by enabling non-neighbor upstream endpoint nodes to replace or remove failed segment identifiers (SIDs) and utilize Interior Gateway Protocol (IGP) shortest paths after IGP convergence, distributing binding protection information through path computation element protocol (PCEP) to ensure continued traffic forwarding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing fast re-route protection mechanisms are used for SR-TE paths, then traffic can be protected against transit node failure before IGP convergence, but traffic is dropped after IGP convergence due to deleted forwarding entries
Solution Approach 1:
The patent pre-computes and stores backup paths and alternative segment identifier lists before failure occurs. When a transit node fails and IGP converges, the upstream endpoint node already has the alternative path information ready, allowing immediate traffic redirection without waiting for post-failure route computation.
Solution Approach 2:
The patent introduces an intermediary mechanism where the upstream endpoint node acts as a mediator between the failed transit node and the rest of the network. It intercepts packets destined for the failed node, removes the failed node's segment identifier, and forwards packets along the alternative path, effectively mediating the traffic flow around the failure.
2Adaptability or versatility
If forwarding entries are deleted after IGP convergence on transit node failure, then routing tables are updated to reflect current network state, but traffic forwarding is interrupted
Solution Approach 1:
The patent applies local quality by making the upstream endpoint node special - it retains and processes alternative path information locally while other nodes follow standard IGP convergence behavior. This localized special handling allows the system to maintain routing table accuracy globally while preserving traffic forwarding continuity at the critical upstream endpoint.
Solution Approach 2:
The patent changes the parameter of segment identifier list manipulation - instead of simply deleting the failed node's segment identifier as conventional approaches do, the system replaces it with an alternative segment identifier list that routes traffic through different nodes, thereby changing the forwarding behavior to maintain continuity.
3Reliability
If conventional FRR mechanisms are implemented, then neighbor upstream nodes can protect traffic, but non-neighbor upstream endpoint nodes cannot extend protection coverage
Solution Approach 1:
The patent makes the upstream endpoint node universal by giving it dual functionality: it serves as both the endpoint that initiates SR-TE paths and as a protection mechanism similar to neighbor upstream nodes. This multi-functionality extends protection coverage beyond just neighbor nodes to include non-neighbor upstream endpoints, thereby improving reliability without proportionally increasing complexity.
Data Source
AI summary
A method comprises receiving a packet, where the packet comprises a binding SID (BSID) of a node and a first list of segment identifiers (SIDs) of a Segment Routing Traffic Engineering (SR-TE) path that includes a first node SID of a non-neighbor upstream endpoint node of the node and a second node SID of the node, the BSID is associated with a second list of SIDs; determining that the second node SID is a failed node SID of the node; removing, in response to the determining, the first node SID and the second node SID from the packet; replacing the BSID in the packet with the second list; and sending the packet to a next hop node on an interior gateway protocol (IGP) shortest path to a destination node after the IGP has converged.