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Status:

EXPERIMENTAL

Authors:

T. Przygienda, Ed.
C. Bowers
Y. Lee
A. Sharma
R. White

Stream:

IETF

Source:

lsr (rtg)

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DOI:  https://doi.org/10.17487/RFC9377

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Abstract

This document describes a backward-compatible, optional IS-ISextension that allows the creation of IS-IS flood reflectiontopologies. Flood reflection permits topologies in which IS-IS Level1 (L1) areas provide transit-forwarding for IS-IS Level 2 (L2) areasusing all available L1 nodes internally. It accomplishes this bycreating L2 flood reflection adjacencies within each L1 area. Thoseadjacencies are used to flood L2 Link State Protocol Data Units(LSPs) and are used in the L2 Shortest Path First (SPF) computation. However, they are not ordinarily utilized for forwarding within theflood reflection cluster. This arrangement gives the L2 topologysignificantly better scaling properties than prevalently used flatdesigns. As an additional benefit, only those routers directlyparticipating in flood reflection are required to support thefeature. This allows for incremental deployment of scalable L1transit areas in an existing, previously flat network design, withoutthe necessity of upgrading all routers in the network.

For the definition ofStatus,seeRFC 2026.

For the definition ofStream, seeRFC 8729.