SR Header Cache Index for Service Function Forwarding
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Solution Overview
Problem
In segment routing (SR) service function chains, when a service function (SF) does not support SR, the service function forwarder (SFF) fails to restore the SR header due to modifications in the 5-tuple of the service packet, leading to failed packet forwarding.
Innovation Solution
The SFF generates cache index information for the SR header, includes it in a packet sent to the SF, and ensures that the cache index information is not modified, allowing the SFF to accurately restore the SR header by matching it with locally cached headers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SFF uses the 5-tuple of the service packet as an index to query and restore the SR header, then the SR header can be restored, but the packet forwarding fails when the SF modifies the 5-tuple
Solution Approach 1:
The patent introduces cache index information as an intermediary element between the SR header and the service packet. The SFF generates cache index information based on the SR header and includes it in the service packet before sending it to the SF. The SF processes the service packet without modifying the cache index information, and returns it to the SFF. The SFF then uses this unchanged cache index information to query and restore the SR header from the cache, ensuring successful packet forwarding even when the SF modifies the 5-tuple of the service packet.
2Adaptability or versatility
If the SFF removes and caches the SR header before forwarding to the SF, then the SR header can be restored later, but the SFF cannot successfully query the cached header when the 5-tuple is modified
Solution Approach 1:
The patent extracts the cache index information from the SR header and places it in the service packet separately. This allows the SR header to be cached using the extracted cache index information as the key, while the service packet carries this index information independently. When the SFF needs to restore the SR header, it queries the cache using the unchanged cache index information from the returned service packet, ensuring accurate retrieval even when the 5-tuple has been modified by the SF.
Data Source
AI summary
A packet transmission method includes: receiving, by a first network device, a first packet sent by a previous-hop device of the first network device, where the first packet includes an SR header; generating, by the first network device, cache index information of the SR header, and storing the cache index information and the SR header; generating, by the first network device, a second packet based on the first packet, where the second packet includes the cache index information but does not include the SR header; and sending, by the first network device, the second packet to a second network device.