Optimization of Parent-node Selection in RPL-based Networks
draft-hou-roll-rpl-parent-selection-00

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ROLL Working Group                                           J. Hou, Ed.
INTERNET-DRAFT                                                 R. Jadhav
Intended Status: Standard Track                                   Z. Luo
Expires: September 13, 2017                          Huawei Technologies
                                                          March 12, 2017

      Optimization of Parent-node Selection in RPL-based Networks 
                 draft-hou-roll-rpl-parent-selection-00

Abstract

   This document describes the problems in the DODAG construction of
   RPL-based network including "Thundering Herd" problem and Randomly
   Unbalanced Networking.  The corresponding optimization methods are
   proposed to improve balancing the selection of parent nodes. 

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Hou, et al             Expires September 13, 2017               [Page 1]
INTERNET DRAFT      Parent Selection in RPL Networks      March 12, 2017

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Requirements Notation and Terminology  . . . . . . . . . .  3
   2.  DODAG Construction and Objective Functions . . . . . . . . . .  3
   3.  Problems with Current DODAG construction . . . . . . . . . . .  4
     3.1.  Problem 1: "Thundering Herd" Phenomenon  . . . . . . . . .  4
     3.2.  Problem 2: Randomly Unbalanced Network . . . . . . . . . .  5
   4.  Optimized Solution . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Solution 1: Increment the ETX_Initial value  . . . . . . .  6
     4.2.  Solution 2: Introducing the Child Node Count Metric  . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

1.  Introduction

   IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) is a
   route-over distance vector routing protocol for networks in
   constrained conditions such as limited power and bandwidth.  This
   protocol defines a Destination Oriented Directed Acyclic Graph
   (DODAG) to avoid the emergence of loops in the network [RFC 6550]. 
   The routing procedure is based on an objective function (OF)
   including a set of metrics/constraints.  The selection of the parent
   node in the RPL-based network directly influences the networking
   balance, and particularly, a poor balance causes the frequent
   switches of parent nodes.  During the switching process, the delayed
   communication directly affects the stability of the entire network,
   so networking balance is an important indicator of the stability of
   mesh network.

   In the RPL-based mesh network, due to the lack of balance algorithm,
   a large batch of nodes possibly select the same parent node and leave
   others empty, turning this focused parent node to be a forwarding
   point.  A higher rate of transmission failure will result in a sharp
   increment in RANK, which triggers all child nodes to re-select and
   switch their parent node, and so on, causing frequent switching of
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