The Trickle Algorithm
RFC 6206

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Internet Engineering Task Force (IETF)                          P. Levis
Request for Comments: 6206                           Stanford University
Category: Standards Track                                     T. Clausen
ISSN: 2070-1721                                 LIX, Ecole Polytechnique
                                                                  J. Hui
                                                   Arch Rock Corporation
                                                              O. Gnawali
                                                     Stanford University
                                                                   J. Ko
                                                Johns Hopkins University
                                                              March 2011

                         The Trickle Algorithm

Abstract

   The Trickle algorithm allows nodes in a lossy shared medium (e.g.,
   low-power and lossy networks) to exchange information in a highly
   robust, energy efficient, simple, and scalable manner.  Dynamically
   adjusting transmission windows allows Trickle to spread new
   information on the scale of link-layer transmission times while
   sending only a few messages per hour when information does not
   change.  A simple suppression mechanism and transmission point
   selection allow Trickle's communication rate to scale logarithmically
   with density.  This document describes the Trickle algorithm and
   considerations in its use.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6206.

Levis, et al.                Standards Track                    [Page 1]
RFC 6206                    Trickle Algorithm                 March 2011

Copyright Notice

   Copyright (c) 2011 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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. Terminology .....................................................3
   3. Trickle Algorithm Overview ......................................3
   4. Trickle Algorithm ...............................................5
      4.1. Parameters and Variables ...................................5
      4.2. Algorithm Description ......................................5
   5. Using Trickle ...................................................6
   6. Operational Considerations ......................................7
      6.1. Mismatched Redundancy Constants ............................7
      6.2. Mismatched Imin ............................................7
      6.3. Mismatched Imax ............................................8
      6.4. Mismatched Definitions .....................................8
      6.5. Specifying the Constant k ..................................8
      6.6. Relationship between k and Imin ............................8
      6.7. Tweaks and Improvements to Trickle .........................9
      6.8. Uses of Trickle ............................................9
   7. Acknowledgements ...............................................10
   8. Security Considerations ........................................10
   9. References .....................................................11
      9.1. Normative References ......................................11
      9.2. Informative References ....................................11

1.  Introduction

   The Trickle algorithm establishes a density-aware local communication
   primitive with an underlying consistency model that guides when a
   node transmits.  When a node's data does not agree with its
   neighbors, that node communicates quickly to resolve the
   inconsistency (e.g., in milliseconds).  When nodes agree, they slow
   their communication rate exponentially, such that nodes send packets
   very infrequently (e.g., a few packets per hour).  Instead of

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