Path Segment Identifier in MPLS-Based Segment Routing Networks
RFC 9545, “Path Segment Identifier in MPLS-Based Segment Routing Networks”, is a Proposed Standard document published in February 2024 by W. Cheng, H. Li, C. Li, R. Gandhi, R. Zigler. The canonical text is published by the RFC Editor.
Abstract
A Segment Routing (SR) path is identified by an SR segment list. A subset of segments from the segment list cannot be leveraged to distinguish one SR path from another as they may be partially congruent. SR path identification is a prerequisite for various use cases such as performance measurement and end-to-end 1+1 path protection.
In an SR over MPLS (SR-MPLS) data plane, an egress node cannot determine on which SR path a packet traversed the network from the label stack because the segment identifiers are removed from the label stack as the packet transits the network.
This document defines a Path Segment Identifier (PSID) to identify an SR path on the egress node of the path.
What “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
The canonical text of RFC 9545 is hosted at rfc-editor.org. Available in HTML,TXT,PDF,XML.
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- RFC 9547 Report from the IAB Workshop on Environmental Impact of Internet Applications and Systems, 2022
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