IGP Flexible Algorithms: Bandwidth, Delay, Metrics, and Constraints
RFC 9843, “IGP Flexible Algorithms: Bandwidth, Delay, Metrics, and Constraints”, is a Proposed Standard document published in September 2025 by S. Hegde, W. Britto, R. Shetty, B. Decraene, P. Psenak, T. Li. It updates RFC 9350. It has since been updated by RFC 9917. The canonical text is published by the RFC Editor.
Abstract
Many networks configure the IGP link metric relative to the link capacity, and high bandwidth traffic gets routed per the link capacity. Flexible Algorithms provide mechanisms to create constraint-based paths in an IGP. This specification documents a generic metric-type and a set of bandwidth-related constraints to be used in Flexible Algorithms.
This document updates RFC 9350.
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 9843 is hosted at rfc-editor.org. Available in HTML,TXT,PDF,XML.
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