IGP Flexible Algorithms (Flex-Algorithm) In IP Networks

Document Type Replaced Internet-Draft (lsr WG)
Authors William Britto  , Shraddha Hegde  , Parag Kaneriya  , Rejesh Shetty  , Ron Bonica  , Peter Psenak 
Last updated 2020-12-20 (latest revision 2020-11-15)
Replaced by draft-ietf-lsr-ip-flexalgo
Stream Internent Engineering Task Force (IETF)
Intended RFC status (None)
Expired & archived
pdf htmlized (tools) htmlized bibtex
Stream WG state Adopted by a WG
Document shepherd No shepherd assigned
IESG IESG state Replaced by draft-ietf-lsr-ip-flexalgo
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute constraint-based paths. As currently defined, IGP Flex-Algorithm is used with Segment Routing (SR) data planes - SR MPLS and SRv6. Therefore, Flex-Algorithm cannot be deployed in the absence of SR. This document extends IGP Flex-Algorithm, so that it can be used for regular IPv4 and IPv6 prefixes. This allows Flex-Algorithm to be deployed in any IP network, even in the absence of SR.


William Britto (bwilliam@juniper.net)
Shraddha Hegde (shraddha@juniper.net)
Parag Kaneriya (pkaneria@juniper.net)
Rejesh Shetty (mrajesh@juniper.net)
Ron Bonica (rbonica@juniper.net)
Peter Psenak (ppsenak@cisco.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)