Avoiding Traffic Black-Holes for Route Aggregation in IS-IS
draft-chen-isis-black-hole-avoid-03

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Last updated 2018-09-06
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Network Working Group                                            Z. Chen
Internet-Draft                                                    Huawei
Intended status: Standards Track                                   X. Xu
Expires: March 9, 2019                                           Alibaba
                                                                D. Cheng
                                                                  Huawei
                                                       September 5, 2018

      Avoiding Traffic Black-Holes for Route Aggregation in IS-IS
                  draft-chen-isis-black-hole-avoid-03

Abstract

   When the Intermediate System to Intermediate System (IS-IS) routing
   protocol is adopted by a highly symmetric network such as the Leaf-
   Spine or Fat-Tree network, the Leaf nodes (e.g., Top of Rack switches
   in datacenters) are recommended to be prevented from receiving other
   nodes' explicit routes in order to achieve scalability.  However,
   such a setup would cause traffic black-holes or suboptimal routing if
   link failure happens in the network.  This document introduces
   INFINITE cost to IS-IS LSPs to solve this problem.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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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   This Internet-Draft will expire on March 9, 2019.

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Copyright Notice

   Copyright (c) 2018 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Description . . . . . . . . . . . . . . . . . . . . .   3
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   When running the Intermediate System to Intermediate System (IS-IS)
   routing protocol in a highly symmetric network such as the Leaf-Spine
   or Fat-Tree network, the Leaf nodes (e.g., Top of Rack switches in
   datacenters) are recommended to be prevented from receiving other
   nodes' explicit routes in order to achieve scalability, as proposed
   in [IS-IS-SL-Extension], [IS-IS-Overhead-Reduction], [RIFT], and
   [OpenFabric].  In particular, each Leaf node SHOULD simply maintain a
   default (or aggregated) route (e.g., 0.0.0.0/0) in its routing table,
   of which the next hop SHOULD be an Equal Cost Multi Path (ECMP) group
   including all Spines nodes that the Leaf node connects to.  However,
   such a setup would cause traffic black-holes or suboptimal routing if
   link failure happens in the network, since the Leaf nodes are not
   aware of any topology information.

   To solve this problem, this document introduces INFINITE cost to IS-
   IS LSPs.  When link failure happens between a Spine node and a Leaf
   node, the Spine node SHOULD advertise all prefixes attached to the
   Leaf node, whose costs SHOULD be set to be INFINITE, to every other
   Leaf node it connects to.  On receiving the prefixes (with INFINITE

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