Overheads Reduction for IS-IS Enabled Spine-Leaf Networks
draft-chen-isis-sl-overheads-reduction-01

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Network Working Group                                            Z. Chen
Internet-Draft                                                     X. Xu
Intended status: Standards Track                     Huawei Technologies
Expires: January 4, 2018                                    July 3, 2017

       Overheads Reduction for IS-IS Enabled Spine-Leaf Networks
               draft-chen-isis-sl-overheads-reduction-01

Abstract

   When a Spine-Leaf topology adopts the Intermediate System to
   Intermediate System (IS-IS) routing protocol, the Leaf node receives
   Link State Packets (LSPs) from all the other nodes thus having the
   entire routing information of the topology.  This is usually
   considered unnecessary and costly.  This document describes a
   solution to this problem by utilizing IS-IS's inherent multi-level
   and area partition features, which requires that an IS-IS router
   SHOULD check a level-1 LSP's area addresses before advertising it to
   a neighbor.

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].

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   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 4, 2018.

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Copyright Notice

   Copyright (c) 2017 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.  Solution Description  . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Area Address Assignment . . . . . . . . . . . . . . . . .   3
     2.2.  Area Address Checking . . . . . . . . . . . . . . . . . .   5
     2.3.  Default Route Advertising . . . . . . . . . . . . . . . .   7
   3.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Overlapping Areas Use Case  . . . . . . . . . . . . . . .   7
     3.2.  Maximum Area Addresses  . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Spine-Leaf topology (a.k.a., CLOS topology) is widely used in today's
   datacenter and campus networks.  When the Spine-Leaf topology runs
   the Intermediate System to Intermediate System (IS-IS) routing
   protocol, each Leaf node receives Link State Packets (LSPs) from all
   the other nodes thus having the entire routing information of the
   topology.  This is usually considered unnecessary and costly because
   the Leaf node only needs to know its default gateways (i.e., the
   Spine nodes it connects to) and the LSPs generated by the other Leaf
   nodes bring little benefit for it to forward traffic.

   To avoid Leaf nodes from learning the unnecessary LSPs from one
   another, [IS-IS-SL-Extension] proposes a new TLV attached to the IS-
   IS Hello (IIH) PDU to carry an router's role (i.e., Spine or Leaf) in
   the topology.  The Spine nodes then prevent all LSPs from being sent

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   to the Leaf nodes, and each Leaf node sets the Spine nodes it
   connects to as its default gateways.

   This document proposes another solution to this problem, which
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