Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-00

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RTGWG Working Group                                                C. Li
Internet-Draft                                                     Z. Hu
Intended status: Standards Track                     Huawei Technologies
Expires: September 12, 2019                               March 11, 2019

    Enhanced Topology Independent Loop-free Alternate Fast Re-route
                   draft-li-rtgwg-enhanced-ti-lfa-00

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.

Status of This Memo

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   This Internet-Draft will expire on September 12, 2019.

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   Copyright (c) 2019 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
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   (https://trustee.ietf.org/license-info) in effect on the date of

Li & Hu                Expires September 12, 2019               [Page 1]
Internet-Draft               Enhanced TI-LFA                  March 2019

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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  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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
   major improvment compared to LFA [RFC5286], and remote LFA [RFC7490]
   which cannot be applicable in some topologies [RFC6571].

   However, the TI-LFA path may skip the node that the active SID points
   to when protecting [Adjacency, Node] segment lists.  For instance,
   the node that a adjacency SID points to is a very important node and
   can not be skipped, such as a firewall node.  When the link between
   the local repair node and firewall node fails, the packets should be
   steered back to the firewall and then forwarding.  But in TI-LFA, if
   the next SID in the SID list is a node SID, the TI-LFA FRR path MAY
   bypass the node that the active segment points to.  Also, if the
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