LFA selection for Multi-Homed Prefixes
draft-ietf-rtgwg-multihomed-prefix-lfa-02

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Last updated 2017-07-25
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Routing Area Working Group                                P. Sarkar, Ed.
Internet-Draft                                                Individual
Updates: 5286 (if approved)                                     S. Hegde
Intended status: Standards Track                               C. Bowers
Expires: January 26, 2018                         Juniper Networks, Inc.
                                                        U. Chunduri, Ed.
                                                     Huawei Technologies
                                                             J. Tantsura
                                                              Individual
                                                             B. Decraene
                                                                  Orange
                                                              H. Gredler
                                                           RtBrick, Inc.
                                                           July 25, 2017

                 LFA selection for Multi-Homed Prefixes
               draft-ietf-rtgwg-multihomed-prefix-lfa-02

Abstract

   This document shares experience gained from implementing algorithms
   to determine Loop-Free Alternates 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 [RFC5286].

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119 [RFC2119].

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
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   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 January 26, 2018                [Page 1]
Internet-Draft   LFA selection for Multi-Homed Prefixes        July 2017

   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 January 26, 2018.

Copyright Notice

   Copyright (c) 2017 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
   (http://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  . . . . . . . . .   4
     3.1.  Improved coverage with simplified approach to MHPs  . . .   6
     3.2.  IS-IS ATT Bit considerations  . . . . . . . . . . . . . .   7
   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  . . . . . . . . . . .   8
       4.2.2.  Multiple ASBRs belonging different area . . . . . . .   9
       4.2.3.  Type 1 and Type 2 costs . . . . . . . . . . . . . . .  10
       4.2.4.  RFC1583compatibility is set to enabled  . . . . . . .  10
       4.2.5.  Type 7 routes . . . . . . . . . . . . . . . . . . . .  10
       4.2.6.  Inequalities to be applied for alternate ASBR
               selection . . . . . . . . . . . . . . . . . . . . . .  10
         4.2.6.1.  Forwarding address set to non-zero value  . . . .  10
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