IPRAN Grid-Ring IGP convergence problems
draft-hares-lsr-grid-ring-convergence-00

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LSR Working Group                                               S. Hares
Internet-Draft                                                    Huawei
Intended status: Informational                         February 11, 2019
Expires: August 15, 2019

                IPRAN Grid-Ring IGP convergence problems
              draft-hares-lsr-grid-ring-convergence-00.txt

Abstract

   This draft describes problems with IGP convergence time in some IPRAN
   networks that use a physical topology of grid backbones that connect
   rings of routers.  Part of these IPRAN network topologies exist in
   data centers with sufficient power and interconnections, but some
   network equipment sits in remote sites impacted by power loss.  In
   some geographic areas these remote sites may be subject to rolling
   blackouts.  These rolling power blackouts could cause multiple
   simultaneous node and link failures.  In these remote networks with
   blackouts, it is often critical that the IPRAN phone network re-
   converge quickly.

   The IGP running in these networks may run in a single level of the
   IGP.  This document seeks to briefly describe these problems to
   determine if the emerging IGP technologies (flexible algorithms,
   dynamic flooding, layers of hierarchy in IGPs) can be applied to help
   reduce convergence times.  It also seeks to determine if the
   improvements of these algorithms or the IP-Fast re-route algorithms
   are thwarted by the failure of multiple link and nodes.

Status of This Memo

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   This Internet-Draft will expire on August 15, 2019.

Hares                    Expires August 15, 2019                [Page 1]
Internet-Draft             IPRAN-IGP-Converge              February 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IPRAN Topologies  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Requirements language . . . . . . . . . . . . . . . . . .   7
   4.  Problem detection using theoretical IGP Convergence . . . . .   8
     4.1.  Equation applied to Data Center IGP Convergence . . . . .   9
     4.2.  Flooding Problem on the Rings . . . . . . . . . . . . . .  11
     4.3.  Flooding problem on the grid  . . . . . . . . . . . . . .  12
   5.  Multiple simultaneous link and node failures  . . . . . . . .  12
     5.1.  Multiple link failures on Ring  . . . . . . . . . . . . .  13
     5.2.  Multiple link failures on Grid  . . . . . . . . . . . . .  14
   6.  Problem with Flat ISIS areas  . . . . . . . . . . . . . . . .  14
   7.  Problems with Dense Flooding Algorithm  . . . . . . . . . . .  15
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  Normative References: . . . . . . . . . . . . . . . . . .  15
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   This draft describes problems with IGP convergence time in some IPRAN
   networks.  The physical topologies of these IPRAN networks combine a
   grid backbone topology with a ring topology to support phone networks
   (see figure 1).  Routers are attached to the rings that route traffic
   from the IPRAN devices (see figure 2).  Each of the rings is attached
   to two grid nodes in order to provide redundancy.  All of the routers
   in the IPRAN ring-grid network topology run a single IGP (IS-IS).

   Some current deployments attach 10-30 routers per ring with a 20 by
   20 grid of routers.  In these deployments, a grid of 400 routers
   supports between 10,000 - 15,000 routers on the IPRAN rings.
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