IS-IS Flooding Scale Considerations
draft-ginsberg-lsr-isis-flooding-scale-00

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Networking Working Group                                     L. Ginsberg
Internet-Draft                                                 P. Psenak
Intended status: Informational                                 A. Lindem
Expires: May 7, 2020                                       Cisco Systems
                                                       November 04, 2019

                  IS-IS Flooding Scale Considerations
               draft-ginsberg-lsr-isis-flooding-scale-00

Abstract

   Link State PDU flooding rates in use are much slower than what modern
   networks can support.  The use of IS-IS at larger scale requires
   faster flooding rates to achieve desired convergence goals.  This
   document discusses issues associated with increasing flooding rates
   and some recommended practices which allow faster flooding rates to
   be used safely.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 May 7, 2020.

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Copyright Notice

   Copyright (c) 2019 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
   Provisions Relating to IETF Documents
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Historical Behavior . . . . . . . . . . . . . . . . . . . . .   3
   3.  Flooding Rate and Convergence . . . . . . . . . . . . . . . .   4
     3.1.  Flow Control  . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Bandwidth Utilization . . . . . . . . . . . . . . . . . .   6
     3.3.  Packet Prioritization on Receive  . . . . . . . . . . . .   7
   4.  Minimizing LSP Generation . . . . . . . . . . . . . . . . . .   7
   5.  Redundant Flooding  . . . . . . . . . . . . . . . . . . . . .   9
   6.  Use of Jumbo Frames . . . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Link state IGPs such as Intermediate-System-to-Intermediate-System
   (IS-IS) depend upon having consistent Link State Databases (LSDB) on
   all Intermediate Systems (ISs) in the network in order to provide
   correct forwarding of data packets.  When topology changes occur,
   new/updated Link State PDUs (LSPs) are propagated network-wide.  The
   speed of propagation is a key contributor to convergence time.

   Historically, flooding rates have been conservative - on the order of
   10s of LSPs/second.  This derives from guidance in the base
   specification [ISO10589] and early deployments when both CPU speeds
   and interface speeds were much slower than they are today and the
   scale of an IS-IS area was smaller than it may be today.

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   As IS-IS is deployed in greater scale (larger number of nodes in an
   area and larger number of neighbors/node) the impact of the historic
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