Use of Abstract NH in Scale-Out peering architecture
draft-szarecki-grow-abstract-nh-scaleout-peering-00

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Internet Engineering Task Force                         R. Szarecki, Ed.
Internet-Draft                                          K. Vairavakkalai
Intended status: Informational                           N. Venkataraman
Expires: August 10, 2019                           Juniper Networks Inc.
                                                        February 6, 2019

          Use of Abstract NH in Scale-Out peering architecture
          draft-szarecki-grow-abstract-nh-scaleout-peering-00

Abstract

   Many large-scale service provider networks use some form of scale-out
   architecture at peering sites.  In such an architecture, each
   participating Autonomous System (AS) deploys multiple independent
   Autonomous System Border Routers (ASBRs) for peering, and Equal Cost
   Multi-Path (ECMP) load balancing is used between them.  There are
   numerous benefits to this architecture, including but not limited to
   N+1 redundancy and the ability to flexibly increase capacity as
   needed.  A cost of this architecture is an increase in the amount of
   state in both the control and data planes.  This has negative
   consequences for network convergence time and scale.

   In this document we describe how to mitigate these negative
   consequences through configuration of the routing protocols, both BGP
   and IGP, to utilize what we term the "Abstract Next-Hop" (ANH).  Use
   of ANH allows us to both reduce the number of BGP paths in the
   control plane and enable rapid path invalidation (hence, network
   convergence and traffic restoration).  We require no new protocol
   features to achieve these benefits.

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   This Internet-Draft will expire on August 10, 2019.

Szarecki, et al.         Expires August 10, 2019                [Page 1]
Internet-Draft      Abstract NH in scale-out peering       February 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Scale-Out peering . . . . . . . . . . . . . . . . . . . .   4
       1.1.1.  Low latency . . . . . . . . . . . . . . . . . . . . .   4
       1.1.2.  All equal cost paths utilization  . . . . . . . . . .   4
       1.1.3.  Summary . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Common BGP Deployment Configurations  . . . . . . . . . .   7
       1.2.1.  IBGP with Next-Hop Unchanged  . . . . . . . . . . . .   7
         1.2.1.1.  Example . . . . . . . . . . . . . . . . . . . . .   7
       1.2.2.  IBGP with Next-Hop-Self . . . . . . . . . . . . . . .   8
   2.  The BGP Abstract Next-Hop . . . . . . . . . . . . . . . . . .   8
   3.  Use of Abstract Next-Hop in scale-out peering design  . . . .   9
     3.1.  Egress ASBR-Peer AS Abstract Next Hop (AP-ANH)  . . . . .  10
     3.2.  The Site-Peer AS Abstract Next Hop (SP-ANH) . . . . . . .  11
     3.3.  Assignment of Abstract Next Hops  . . . . . . . . . . . .  14
       3.3.1.  Native IP Networks  . . . . . . . . . . . . . . . . .  14
       3.3.2.  MPLS  . . . . . . . . . . . . . . . . . . . . . . . .  14
         3.3.2.1.  Identical BGP address space and paths received on
                   all ASBRs . . . . . . . . . . . . . . . . . . . .  14
         3.3.2.2.  Different address space sets or paths received on
                   different ASBRs . . . . . . . . . . . . . . . . .  14
       3.3.3.  SPRING  . . . . . . . . . . . . . . . . . . . . . . .  15
         3.3.3.1.  Identical BGP address space and path received on
                   all ASBRs . . . . . . . . . . . . . . . . . . . .  15
         3.3.3.2.  Different address space sets or paths received on
                   different ASBRs . . . . . . . . . . . . . . . . .  15
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