SR-TE Stitching Label Replacement for Backup Path Switching
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Solution Overview
Problem
In Segment Routing-Traffic Engineering (SR-TE), when a stitching node on the primary path fails, the previous-hop node cannot process the stitching label, leading to packet forwarding failures due to the inability to switch the packet to a backup path.
Innovation Solution
The stitching node advertises the stitching label and its label stack across the network, enabling the previous-hop node to replace the stitching label with the stitching label stack, allowing the packet to be switched to a backup path for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fast reroute technology is used to forward packets through backup paths when a node fails, then network reliability is improved, but packet forwarding fails when the faulty node is a stitching node because the previous-hop node cannot process the stitching label
Solution Approach 1:
The stitching node advertises the stitching label and stitching label stack list to the previous-hop node in advance through IGP protocols before any fault occurs. This preliminary action ensures that when a fault happens, the previous-hop node already has the necessary information to process the stitching label and switch packets to backup paths without failure.
Solution Approach 2:
The stitching label stack list acts as an intermediary mechanism that bridges the gap between the stitching node's label processing capability and the previous-hop node's forwarding needs. By replacing the stitching label with the stitching label stack list at the previous-hop node, the system enables the previous-hop node to indirectly access the stitching node's label processing functionality.
2Productivity
If the stitching node processes the stitching label, then correct packet forwarding is achieved, but the previous-hop node cannot forward packets correctly because it cannot process the stitching label
Solution Approach 1:
The stitching node advertises not only the stitching label but also the complete stitching label stack list to multiple nodes in the network including the previous-hop node. This universal dissemination of label information enables both the stitching node and previous-hop node to handle packet forwarding, making the system more versatile and less dependent on a single node's processing capability.
Data Source
AI summary
This application discloses a transmission path fault processing method and apparatus, and a system, to resolve a problem that a packet fails to be forwarded because a previous-hop node of a faulty node cannot process a stitching label. The method includes: receiving, by a first network device, a stitching label and a stitching label stack list corresponding to the stitching label that are sent by a stitching network device; determining, in a process of sending a packet through a primary path, that the stitching network device is faulty, where the packet includes a label stack list, and the stitching network device is a next-hop network device of the first network device; and replacing, by the first network device, the stitching label in the label stack list with the stitching label stack list, and switching, based on the updated label stack list, the packet to a backup path for sending.