Deterministic SRv6 S-BFD Reply Path via Segmented Headers
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Solution Overview
Problem
Segment Routing over Internet Protocol version 6 (SRv6) networks face challenges with unidirectional TE tunnels, making Seamless-Bidirectional Forwarding Detection (S-BFD) and ping replies unreliable due to indeterministic return paths, which can lead to failed monitoring of network availability and fault detection.
Innovation Solution
The implementation of deterministic reply paths for S-BFD and ping packets using standard IPv6 headers and SRv6 extensions, including the use of SRv6 return paths and a new Type-Length-Value (TLV) for controlled ICMPv6 reply frames, ensures that replies follow the same path as requests, eliminating the need for additional control streams and simplifying configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If unidirectional TE tunnels are used in SRv6 networks, then forwarding efficiency is improved, but monitoring reliability deteriorates due to indeterministic return paths
Solution Approach 1:
The patent segments the routing path into forward and reverse components by encoding separate segment lists in the monitoring packet header. The forward path uses one SRv6 tunnel while the reverse path uses another, allowing independent optimization of each direction. This segmentation resolves the contradiction by enabling unidirectional forward tunnels for efficiency while establishing a separate controlled return path for monitoring reliability.
Solution Approach 2:
The patent performs preliminary action by pre-encoding the reverse path segment list in the monitoring packet before transmission. The headend node prepares both forward and reverse segment lists in advance, ensuring the reply packet will follow a deterministic path back without requiring real-time route determination. This preliminary configuration guarantees monitoring reliability while maintaining forwarding efficiency.
2Reliability
If additional control streams are implemented for deterministic reply paths, then monitoring reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the monitoring packet header structure universal by designing it to carry both forward and reverse segment lists in a standardized format. This multi-functional header can accommodate different SRv6 tunnel configurations and monitoring types (S-BFD, ping, traceroute) without requiring separate control streams or additional protocol structures, thereby improving reliability without increasing device complexity.
Solution Approach 2:
The patent merges the forward and reverse path information into a single monitoring packet by encoding both segment lists in the packet header. Instead of using separate control streams for forward and reverse paths, the solution combines both routing instructions in one packet, reducing configuration complexity while ensuring deterministic reply paths for improved monitoring reliability.
3Adaptability or versatility
If standard IPv6 headers and SRv6 extensions are used for deterministic paths, then interoperability is improved, but configuration complexity increases due to path control requirements
Solution Approach 1:
The patent changes the parameters of existing SRv6 headers by utilizing and extending standard IPv6 header fields and SRv6 extension headers to carry additional path control information. By modifying existing parameter structures rather than introducing new header formats, the solution maintains interoperability with standard SRv6 implementations while enabling deterministic reply paths. The configuration complexity is managed by reusing existing parameter spaces.
Data Source
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AI summary
A node (100) is configured to operate in a Segment Routing (SR) over Internet Protocol version 6 (SRv6) network (10), and the node (100) includes circuitry configured to determine (302) a Segment Identifier (SID) list for a forward path in the SRv6 network and SID list for a reverse path in the SRv6 network; and transmit (304) a monitoring packet on the forward path including a Segment Routing Header (SRH) with the SID list for the forward path, and further including the SID list for the reverse path in the monitoring packet, for a SRH of a reply to the monitoring packet. The circuitry can be further configured to receive (306) the reply to the monitoring packet, with the reply having been on a same or different tunnel as the monitoring packet, for monitoring liveliness thereof.