Objective Function Zero for the Routing Protocol for Low-Power and Lossy Networks (RPL)
RFC 6552

Internet Engineering Task Force (IETF)                   P. Thubert, Ed.
Request for Comments: 6552                                 Cisco Systems
Category: Standards Track                                     March 2012
ISSN: 2070-1721

                    Objective Function Zero for the
        Routing Protocol for Low-Power and Lossy Networks (RPL)

Abstract

   The Routing Protocol for Low-Power and Lossy Networks (RPL)
   specification defines a generic Distance Vector protocol that is
   adapted to a variety of network types by the application of specific
   Objective Functions (OFs).  An OF states the outcome of the process
   used by a RPL node to select and optimize routes within a RPL
   Instance based on the Information Objects available; an OF is not an
   algorithm.

   This document specifies a basic Objective Function that relies only
   on the objects that are defined in the RPL and does not use any
   protocol extensions.

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/rfc6552.

Copyright Notice

   Copyright (c) 2012 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

Thubert                      Standards Track                    [Page 1]
RFC 6552               RPL Objective Function Zero            March 2012

   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 .....................................................4
   3. Objective Function Zero Overview ................................4
   4. OF0 Operations ..................................................5
      4.1. Computing Rank .............................................5
      4.2. Parent Selection ...........................................7
           4.2.1. Selection of the Preferred Parent ...................7
           4.2.2. Selection of the Backup Feasible Successor ..........8
   5. Abstract Interface to OF0 .......................................9
   6. OF0 Operands ....................................................9
      6.1. Variables ..................................................9
      6.2. Configurable Parameters ...................................10
      6.3. Constants .................................................10
   7. Manageability Considerations ...................................10
      7.1. Device Configuration ......................................11
      7.2. Device Monitoring .........................................11
   8. IANA Considerations ............................................12
   9. Security Considerations ........................................12
   10. Acknowledgements ..............................................12
   11. References ....................................................13
      11.1. Normative References .....................................13
      11.2. Informative References ...................................13

1.  Introduction

   The Routing Protocol for Low-Power and Lossy Networks (RPL)
   specification [RFC6550] defines a generic Distance Vector protocol
   that is adapted to a variety of Low-Power and Lossy Network (LLN)
   types by the application of specific Objective Functions (OFs).

   A RPL OF states the outcome of the process used by a RPL node to
   select and optimize routes within a RPL Instance based on the
   Information Objects available.  As a general concept, an OF is not an
   algorithm.  For example, outside RPL, "shortest path first" is an OF
   where the least cost path between two points is derived as an
   outcome; there are a number of algorithms that can be used to satisfy
   the OF, of which the well-known Dijkstra algorithm is an example.

   The separation of OFs from the core protocol specification allows RPL