Prefix Unreachable Announcement
draft-wang-lsr-prefix-unreachable-annoucement-06

Document Type Active Internet-Draft (individual)
Authors Aijun Wang  , Gyan Mishra  , Zhibo Hu , Yaqun Xiao 
Last updated 2021-03-25
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LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                               G. Mishra
Expires: September 27, 2021                                 Verizon Inc.
                                                                   Z. Hu
                                                                 Y. Xiao
                                                     Huawei Technologies
                                                          March 26, 2021

                    Prefix Unreachable Announcement
            draft-wang-lsr-prefix-unreachable-annoucement-06

Abstract

   This document describes a mechanism to solve an existing issue with
   Longest Prefix Match (LPM), that exists where an operator domain is
   divided into multiple areas or levels where summarization is
   utilized.  This draft addresses a fail-over issue related to a multi
   areas or levels domain, where a link or node down event occurs
   resulting in an LPM component prefix being omitted from the FIB
   resulting in black hole sink of routing and connectivity loss.  This
   draft introduces a new control plane convergence signaling mechanism
   using a negative prefix called Prefix Unreachable Announcement (PUA),
   utilized to detect a link or node down event and signal the RIB that
   the event has occurred to force immediate control plane convergence.

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
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   This Internet-Draft will expire on September 27, 2021.

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Copyright Notice

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Scenario Description  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Inter-Area Node Failure Scenario  . . . . . . . . . . . .   4
     3.2.  Inter-Area Links Failure Scenario . . . . . . . . . . . .   4
   4.  PUA (Prefix Unreachable Advertisement) Procedures . . . . . .   5
   5.  MPLS and SRv6 LPM based BGP Next-hop Failure Application  . .   5
   6.  Implementation Consideration  . . . . . . . . . . . . . . . .   6
   7.  Deployment Considerations . . . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   7
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   As part of an operator optimized design criteria, a critical
   requirement is to limit Shortest Path First (SPF) churn which occurs
   within a single OSPF area or ISIS level.  This is accomplished by
   sub-dividing the IGP domain into multiple areas for flood reduction
   of intra area prefixes so they are contained within each discrete
   area to avoid domain wide flooding.

   OSPF and ISIS have a default and summary route mechanism which is
   performed on the OSPF area border router or ISIS L1-L2 node.  The
   OSPF summary route is triggered to be advertised conditionally when
   at least one component prefix exists within the non-zero area.  ISIS
   Level-L1-L2 node as well generate a summary prefix into the level-2
   backbone area for Level 1 area prefixes that is triggered to be
   advertised conditionally when at least a single component prefix

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