IS-IS Optimal Distributed Flooding for Dense Topologies
draft-white-lsr-distoptflood-00
Network Working Group R. White
Internet-Draft S. Hegde
Intended status: Informational Juniper Networks
Expires: June 2, 2021 S. Zandi
LinkedIn
November 29, 2020
IS-IS Optimal Distributed Flooding for Dense Topologies
draft-white-lsr-distoptflood-00
Abstract
In dense topologies, such as data center fabrics based on the Clos
and butterfly fabric topologies, flooding mechanisms designed for
sparse topologies, when used in these dense topologies, can
"overflood," or carry too many copies of topology and reachability to
fabric devices. This results in slower convergence times and higher
resource utilization. The modifications to the flooding mechanism in
the Intermediate System to Intermediate System (IS-IS) link state
protocol described in this document reduce resource utilization to a
minimum, while increaseing convergence performance in dense
topologies.
Note that a Clos fabric is used as the primary example of a desne
flooding topology throughout this document. However, the flooding
optimizations described in this document apply to any dense topology.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 2, 2021.
White, et al. Expires June 2, 2021 [Page 1]
Internet-DraftIS-IS Optimal Distributed Flooding for Dense November 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Contributors . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Experience . . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Sample Network . . . . . . . . . . . . . . . . . . . . . 3
2. Flooding Modifications . . . . . . . . . . . . . . . . . . . 5
2.1. Optimizing Flooding . . . . . . . . . . . . . . . . . . . 5
2.2. Flooding Failures . . . . . . . . . . . . . . . . . . . . 6
3. Use of Flooding Leaders and Flooding Mechanism Advertisements 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Flooding Optimization Operation . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
1.1. Goals
The goal of this draft is to solve one specific set of problems
involved in operating a link state protocol in a dense mesh topology.
The problem with such topologies is the connectivity density, which
causes too much information to be flooded (or too much repeated state
to be flooded). Analysis and experiment show, for instance, that in
a butterfly fabric of around 2500 intermediate systems, each
intermediate system will receive 40+ copies of any changed LSP
fragment. This not only wastes bandwidth and processor time, this
dramatically slows convergence speed.
White, et al. Expires June 2, 2021 [Page 2]
Internet-DraftIS-IS Optimal Distributed Flooding for Dense November 2020
This document describes a set of modifications to existing IS-IS
flooding mechanisms which minimize the number of LSP framgents
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