{"draft":"draft-ietf-lsr-isis-flood-reflection-12","doc_id":"RFC9377","title":"IS-IS Flood Reflection","authors":["T. Przygienda, Ed.","C. Bowers","Y. Lee","A. Sharma","R. White"],"format":["HTML","TEXT","PDF","XML"],"page_count":"19","pub_status":"EXPERIMENTAL","status":"EXPERIMENTAL","source":"Link State Routing","abstract":"This document describes a backward-compatible, optional IS-IS\r\nextension that allows the creation of IS-IS flood reflection\r\ntopologies. Flood reflection permits topologies in which IS-IS Level\r\n1 (L1) areas provide transit-forwarding for IS-IS Level 2 (L2) areas\r\nusing all available L1 nodes internally.  It accomplishes this by\r\ncreating L2 flood reflection adjacencies within each L1 area. Those\r\nadjacencies are used to flood L2 Link State Protocol Data Units\r\n(LSPs) and are used in the L2 Shortest Path First (SPF) computation. \r\nHowever, they are not ordinarily utilized for forwarding within the\r\nflood reflection cluster.    This arrangement gives the L2 topology\r\nsignificantly better scaling properties than prevalently used flat\r\ndesigns.  As an additional benefit, only those routers directly\r\nparticipating in flood reflection are required to support the\r\nfeature.  This allows for incremental deployment of scalable L1\r\ntransit areas in an existing, previously flat network design, without\r\nthe necessity of upgrading all routers in the network.","pub_date":"April 2023","keywords":[],"obsoletes":[],"obsoleted_by":[],"updates":[],"updated_by":[],"see_also":[],"doi":"10.17487\/RFC9377","errata_url":null}