BGP Prefix Independent Convergence
draft-ietf-rtgwg-bgp-pic-11

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Network Working Group                                  A. Bashandy, Ed.
Internet Draft                                   Individual Contributor
Intended status: Informational                              C. Filsfils
Expires: August 2020                                      Cisco Systems
                                                           P. Mohapatra
                                                       Sproute Networks
                                                      February 10, 2020

                    BGP Prefix Independent Convergence
                      draft-ietf-rtgwg-bgp-pic-11.txt

Abstract

In the network comprising thousands of iBGP peers exchanging millions
of routes, many routes are reachable via more than one next-hop.
Given the large scaling targets, it is desirable to restore traffic
after failure in a time period that does not depend on the number of
BGP prefixes. In this document we proposed an architecture by which
traffic can be re-routed to ECMP or pre-calculated backup paths in a
timeframe that does not depend on the number of BGP prefixes. The
objective is achieved through organizing the forwarding data
structures in a hierarchical manner and sharing forwarding elements
among the maximum possible number of routes. The proposed technique
achieves prefix independent convergence while ensuring incremental
deployment, complete automation, and zero management and provisioning
effort. It is noteworthy to mention that the benefits of BGP-PIC are
hinged on the existence of more than one path whether as ECMP or
primary-backup.

Status of this Memo

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Bashandy              Expires August 10, 2020                 [Page 1]
Internet-Draft    BGP Prefix Independent Convergence      February 2020

   The list of Internet-Draft Shadow Directories can be accessed at
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   This Internet-Draft will expire on August 10, 2020.

Copyright Notice

   Copyright (c) 2020 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
      1.1. Terminology...............................................3
   2. Overview.......................................................5
      2.1. Dependency................................................6
         2.1.1. Hierarchical Hardware FIB............................6
         2.1.2. Availability of more than one BGP next-hops..........6
      2.2. BGP-PIC Illustration......................................7
   3. Constructing the Shared Hierarchical Forwarding Chain..........9
      3.1. Constructing the BGP-PIC forwarding Chain.................9
      3.2. Example: Primary-Backup Path Scenario....................10
   4. Forwarding Behavior...........................................11
   5. Handling Platforms with Limited Levels of Hierarchy...........12
      5.1. Flattening the Forwarding Chain..........................12
      5.2. Example: Flattening a forwarding chain...................14
   6. Forwarding Chain Adjustment at a Failure......................21
      6.1. BGP-PIC core.............................................22
      6.2. BGP-PIC edge.............................................23
         6.2.1. Adjusting forwarding Chain in egress node failure...23
         6.2.2. Adjusting Forwarding Chain on PE-CE link Failure....23
      6.3. Handling Failures for Flattened Forwarding Chains........24
   7. Properties....................................................25
      7.1. Coverage.................................................25
         7.1.1. A remote failure on the path to a BGP next-hop......25
         7.1.2. A local failure on the path to a BGP next-hop.......25