Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-03

Document Type Active Internet-Draft (individual)
Authors Cheng Li  , Zhibo Hu , Yongqing Zhu  , Shraddha Hegde 
Last updated 2020-10-30
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RTGWG Working Group                                                C. Li
Internet-Draft                                                     Z. Hu
Intended status: Standards Track                     Huawei Technologies
Expires: May 5, 2021                                              Y. Zhu
                                                           China Telecom
                                                                S. Hegde
                                                   Juniper Networks Inc.
                                                        November 1, 2020

    Enhanced Topology Independent Loop-free Alternate Fast Re-route
                   draft-li-rtgwg-enhanced-ti-lfa-03

Abstract

   Topology Independent Loop-free Alternate Fast Re-route (TI-LFA) aims
   at providing protection of node and adjacency segments within the
   Segment Routing (SR) framework.  A key aspect of TI-LFA is the FRR
   path selection approach establishing protection over the expected
   post-convergence paths from the point of local repair.  However, the
   TI-LFA FRR path may skip the node even if it is specified in the SID
   list to be traveled.

   This document defines Enhanced TI-LFA(TI-LFA+) by adding a No-bypass
   indicator for segments to ensure that the FRR route will not bypass
   the specific node, such as firewall.  Also, this document defines No-
   bypass flag and No-FRR flag in SRH to indicate not to bypass nodes
   and not to perform FRR on all the nodes along the SRv6 path,
   respectively.

Status of This Memo

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   This Internet-Draft will expire on May 5, 2021.

Li, et al.                 Expires May 5, 2021                  [Page 1]
Internet-Draft               Enhanced TI-LFA               November 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  Overview of Enhanced TI-LFA . . . . . . . . . . . . . . . . .   3
   4.  IGP Protocol Extensions . . . . . . . . . . . . . . . . . . .   4
     4.1.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Flags in SRH  . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  No-bypass Flag in SRH . . . . . . . . . . . . . . . . . .   8
     5.2.  No-FRR Flag in SRH  . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Segment Routing [RFC8402] enables to steer packets by explicitly
   encoding instructions in the data packets at the source node to
   support services like traffic engineer.  Relying on SR,
   [I-D.ietf-rtgwg-segment-routing-ti-lfa] defines Topology Independent
   Loop-free Alternate Fast Re-route (TI-LFA), a local repair mechanism
   for IGP shortest path that capable of restoring end-to-end
   connectivity in the case of a sudden directly connected failure of a
   network component.

   TI-LFA supports to establish a loop free backup path over the
   expected post-convergence paths from the point of local repair
   irrespective of the topologies used in the network, which provides a
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