Experimental observation of RPL: routing protocol overhead and asymmetric links

Document Type Active Internet-Draft (individual)
Last updated 2019-03-11
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
Network Working Group                                         H. Audeoud
Internet-Draft                                                 M. Heusse
Intended status: Informational                                       LIG
Expires: September 12, 2019                               March 11, 2019

     Experimental observation of RPL: routing protocol overhead and
                            asymmetric links


   This document summarizes our observations of the behavior of RPL on a
   testbed composed of tens of IEEE 802.15.4 nodes.  Our first
   observation is that the continuous task of estimating the link metric
   to all candidate neighbors causes a significant background load.
   This traffic is persistent, even in a stable network where DIO
   transmissions are eventually widely spaced.  Next, this document
   focuses on the case of the presence of an asymmetric link, due to
   either a muted or a deaf node.  In these circumstances, the standard
   RPL mechanisms may well generate hundreds of routing messages per
   node and per hour.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 12, 2019.

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
   (https://trustee.ietf.org/license-info) in effect on the date of

Audeoud & Heusse       Expires September 12, 2019               [Page 1]
Internet-DraExperimental observation of RPL: routing protoco  March 2019

   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.

1.  Introduction

   We present three cases in which the RPL protocol [RFC6550] incurs a
   large number of routing message transmissions even though they
   correspond to expected situations in LLNs.  This memo summarizes our
   observations on RPL that are part of a broader set of experiments

1.1.  Convergence and background traffic

   The maintenance traffic in RPL converges to a low rate of DIO
   generation when the topology is stable.  Nevertheless, the proactive
   approach of RPL imposes that the nodes permanently gauge potential
   new alternative neighbors.  This mechanism is not standardized, but
   it is necessary.  Users need to be aware of its existence and its

1.2.  Asymmetric links

   The quality of radio transmissions depends on the environment and on
   the radio hardware.  In particular, interferences do not have the
   same impact on all nodes.  Also, the transmission conditions are
   different between devices due to the variability of the amplifier
   gain and sensitivity.

   So a link between two nodes may be asymmetric, and not present the
   same packet delivery ratios (PDR) in both directions.  In extreme
   cases, a node N may be "deaf" (i.e. other nodes receive N's packets,
   but N does not receive anything back) or "muted" (i.e.  N receives
   properly, but is not heard).

1.3.  Experimental setup

   Table 1 presents the parameters used in the experiments.  The trickle
   settings match the recommended practice, with Imin more than one
   order of magnitude greater than the broadcast duration (125
   milliseconds in ContikiMAC).  We found that this setting effectively
   avoids DIO collisions in our experiments.

Audeoud & Heusse       Expires September 12, 2019               [Page 2]
Internet-DraExperimental observation of RPL: routing protoco  March 2019

   | Parameter                   | Value                               |
   | Platform                    | IoT-lab                             |
   |                             |                                     |
   | Sensors                     | IoT-lab's M3 motes (ARM Cortex M3   |
   |                             | STM32F103REY)                       |
Show full document text