LFA selection for Multi-Homed Prefixes
draft-ietf-rtgwg-multihomed-prefix-lfa-08

Document Type Active Internet-Draft (rtgwg WG)
Last updated 2018-10-25 (latest revision 2018-10-16)
Replaces draft-chunduri-rtgwg-lfa-extended-procedures, draft-psarkar-rtgwg-multihomed-prefix-lfa
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication
Document shepherd Stewart Bryant
Shepherd write-up Show (last changed 2018-02-08)
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Send notices to Stewart Bryant <stewart.bryant@gmail.com>
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Routing Area Working Group                                P. Sarkar, Ed.
Internet-Draft                                              Arrcus, Inc.
Updates: 5286 (if approved)                             U. Chunduri, Ed.
Intended status: Standards Track                              Huawei USA
Expires: April 19, 2019                                         S. Hegde
                                                  Juniper Networks, Inc.
                                                             J. Tantsura
                                                            Apstra, Inc.
                                                              H. Gredler
                                                           RtBrick, Inc.
                                                        October 16, 2018

                 LFA selection for Multi-Homed Prefixes
               draft-ietf-rtgwg-multihomed-prefix-lfa-08

Abstract

   This document shares experience gained from implementing algorithms
   to determine Loop-Free Alternates (LFAs) for multi-homed prefixes.
   In particular, this document provides explicit inequalities that can
   be used to evaluate neighbors as a potential alternates for multi-
   homed prefixes.  It also provides detailed criteria for evaluating
   potential alternates for external prefixes advertised by OSPF ASBRs.
   This documents updates and expands some of the "Routing Aspects" as
   specified in Section 6 of RFC 5286.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 RFC8174 [RFC2119] RFC8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

Sarkar, et al.           Expires April 19, 2019                 [Page 1]
Internet-Draft   LFA selection for Multi-Homed Prefixes     October 2018

   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 19, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  LFA inequalities for MHPs . . . . . . . . . . . . . . . . . .   4
   3.  LFA selection for the multi-homed prefixes  . . . . . . . . .   5
     3.1.  Improved coverage with simplified approach to MHPs  . . .   6
     3.2.  IS-IS ATT Bit considerations  . . . . . . . . . . . . . .   8
   4.  LFA selection for the multi-homed external prefixes . . . . .   8
     4.1.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  Rules to select alternate ASBR  . . . . . . . . . . .   9
         4.2.1.1.  Multiple ASBRs belonging different area . . . . .  11
         4.2.1.2.  Type 1 and Type 2 costs . . . . . . . . . . . . .  11
         4.2.1.3.  RFC1583compatibility is set to enabled  . . . . .  11
         4.2.1.4.  Type 7 routes . . . . . . . . . . . . . . . . . .  11
       4.2.2.  Inequalities to be applied for alternate ASBR
               selection . . . . . . . . . . . . . . . . . . . . . .  12
         4.2.2.1.  Forwarding address set to non-zero value  . . . .  12
         4.2.2.2.  ASBRs advertising type1 and type2 cost  . . . . .  12
   5.  LFA Extended Procedures . . . . . . . . . . . . . . . . . . .  13
     5.1.  Links with IGP MAX_METRIC . . . . . . . . . . . . . . . .  13
     5.2.  Multi Topology Considerations . . . . . . . . . . . . . .  14
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