BIER Fast Reroute
draft-merling-bier-frr-00

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BIER Working Group                                            D. Merling
Internet-Draft                                                  M. Menth
Intended status: Standards Track                 University of Tuebingen
Expires: September 6, 2019                                March 05, 2019

                           BIER Fast Reroute
                       draft-merling-bier-frr-00

Abstract

   BIER is a scalable multicast overlay [RFC8279] that utilizes some
   routing underlay, e.g., IP, to build up its Bit Index Forwarding
   Tables (BIFTs).  This document proposes a Fast Reroute Extension for
   BIER (BIER-FRR).  In case of a link or node failure, the routing
   underlay may first utilize FRR techniques to restore connectivity and
   then its forwarding tables converge.  After that, BIER can update its
   BIFTs, which requires time.  BIER packets may not be delivered until
   the last procedure has finished.  With BIER-FRR, a BIER Forwarding
   Router (BFR) can deliver BIER packets again after a link or node
   failures as soon as the connectivity within the routing underlay is
   restored and the BFR is informed about a next-hop (NH) that is
   unreachable on a lower layer.  BIER-FRR provides a mode for link
   protection and node protection.  For link protection, it tunnels
   traffic to the next-hop using the underlying routing.  For node
   protection, it forwards BIER packets to their specific next-hop and
   next-next-hops using tunnels in the underlying routing after applying
   a suitable backup bitmask to the bitstring in the BIER header of each
   packet.  This procedure prevents duplicates.  If topology allows,
   BIER-FRR achieves full protection against any single component
   failure.  For link protection, BIER-FRR requires only a minor change
   to the forwarding logic.  For node protection, BIER-FRR also requires
   backup entries in the BIFT.

   This document describes the concept and operating principles of BIER-
   FRR.  It defines the necessary modifications to the BIER forwarding
   Procedure and the BIFT, and explains how backup entries are computed.

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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Merling & Menth         Expires September 6, 2019               [Page 1]
Internet-Draft                  BIER-FRR                      March 2019

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on September 6, 2019.

Copyright Notice

   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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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   6
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Link Failures . . . . . . . . . . . . . . . . . . . . . .   6
       3.1.1.  BIER Encapsulation within a Lower-Layer Technology
               with Protection . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  BIER Encapsulation within the Routing Underlay  . . .   6
       3.1.3.  BIER Encapsulation within a Lower-Layer Technology
               without Protection  . . . . . . . . . . . . . . . . .   7
     3.2.  Node Failures . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Fast Reroute Extension for BIER (BIER-FRR)  . . . . . . . . .   7
     4.1.  BIER-FRR Link Protection  . . . . . . . . . . . . . . . .   7
       4.1.1.  Mechanism . . . . . . . . . . . . . . . . . . . . . .   8
       4.1.2.  Example . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  BIER-FRR Node Protection  . . . . . . . . . . . . . . . .   8
       4.2.1.  Mechanism . . . . . . . . . . . . . . . . . . . . . .   8
       4.2.2.  Example . . . . . . . . . . . . . . . . . . . . . . .  10
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