IGP Flexible Algorithms (Flex-Algorithm) In IP Networks
draft-ietf-lsr-ip-flexalgo-00

Document Type Active Internet-Draft (lsr WG)
Authors William Britto  , Shraddha Hegde  , Parag Kaneriya  , Rejesh Shetty  , Ron Bonica  , Peter Psenak 
Last updated 2020-12-23
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LSR Working Group                                              W. Britto
Internet-Draft                                                  S. Hegde
Intended status: Standards Track                             P. Kaneriya
Expires: June 26, 2021                                         R. Shetty
                                                               R. Bonica
                                                        Juniper Networks
                                                               P. Psenak
                                                           Cisco Systems
                                                       December 23, 2020

        IGP Flexible Algorithms (Flex-Algorithm) In IP Networks
                     draft-ietf-lsr-ip-flexalgo-00

Abstract

   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.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on June 26, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Britto, et al.            Expires June 26, 2021                 [Page 1]
Internet-Draft              IP Flex-Algorithm              December 2020

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Egress Node Procedures  . . . . . . . . . . . . . . . . . . .   3
   4.  Advertising Flex-Algorithm Definitions (FAD)  . . . . . . . .   3
   5.  Advertising IP Flex-Algorithm Participation . . . . . . . . .   3
     5.1.  The ISIS IP Algorithm Sub-TLV . . . . . . . . . . . . . .   4
     5.2.  The OSPF IP Algorithm TLV . . . . . . . . . . . . . . . .   5
   6.  Advertising IP Flex-Algorthm Reachability . . . . . . . . . .   6
     6.1.  The ISIS IPv4 Algorithm Prefix Reachability TLV . . . . .   6
     6.2.  The ISIS IPv6 Algorithm Prefix Reachability TLV . . . . .   8
     6.3.  The OSPFv2 Algorithm Prefix Reachability TLV  . . . . . .   9
     6.4.  The OSPFv3 Flex-Algorithm IP Prefix Opaque LSA  . . . . .  11
   7.  Calculating of IP Flex-Algorthm Paths . . . . . . . . . . . .  11
   8.  IP Flex-Algorthm Forwarding . . . . . . . . . . . . . . . . .  12
   9.  Deployment Considerations . . . . . . . . . . . . . . . . . .  12
   10. Protection  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     14.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   An IGP Flex-Algorithm as specified in [I-D.ietf-lsr-flex-algo]
   computes a constraint-based path to:

   o  All Flex-Algorithm specific Prefix Segment Identifiers (SIDs)
      [RFC8402].

   o  All Flex-Algorityhm specific SRv6 Locators
      [I-D.ietf-spring-srv6-network-programming].

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   Therefore, Flex-Algorithm cannot be deployed in the absence of SR and
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