Use cases for DIS Modifications
draft-papadopoulos-roll-dis-mods-use-cases-00

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RAW                                                      G. Papadopoulos
Internet-Draft                                            IMT Atlantique
Intended status: Standards Track                           March 9, 2020
Expires: September 10, 2020

                    Use cases for DIS Modifications
             draft-papadopoulos-roll-dis-mods-use-cases-00

Abstract

   This document presents some of the use-cases which call for DIS flags
   and options modifications.

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   This Internet-Draft will expire on September 10, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Applications  . . . . . . . . . . . . . . . . . . . . . . . .   2
     3.1.  A Leaf Node Joining a DAG . . . . . . . . . . . . . . . .   2
     3.2.  Identifying A Defunct DAG . . . . . . . . . . . . . . . .   3
     3.3.  Adjacencies probing with RPL  . . . . . . . . . . . . . .   5
       3.3.1.  Deliberations . . . . . . . . . . . . . . . . . . . .   6
   4.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Applications

   This section details some use cases that require DIS modifications
   compared to the behaviour currently defined in [RFC6550].  The first
   use case is thatof a new leaf node joining an established DAG in an
   energy efficient manner.  The second use case describes why node
   might want to use DIS to identify defunct DAGs for which it still
   maintains state.  The third use case describes the need for adjacency
   probing and how DIS can used for that.

3.1.  A Leaf Node Joining a DAG

   This use case is typically of a smart meter being replaced in the
   field, while a RPL network is operating and stable.  The new smart
   meter must join the network quickly, without draining the energy of
   the surrounding nodes, be they battery-operated RPL routers or leaf
   nodes.  In this use case, the issues with the current RPL
   specification are

   o  Just waiting for a gratuitous DIO may take a long time if the
      Trickle timers have relaxed to the steady state.  A technician who
      has just installed the new meter needs to positively assess that
      the meter has joined the network before it leaves the premise.  It
      is not economically viable to ask the technician to standby the
      meter until a gratuitous DIO has arrived, which may take hours.

   o  If the meter sends a DIS, it needs to do so using multicast,
      because it has no knowledge of its surroundings.  Sending a

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      multicast DIS is considered an inconsistency by the nearby RPL
      routers.  They will reset their Trickle timer to the shortest
      period.  This will trigger sending a stream of DIOs until the
      Trickle timers relax again.  The DIOs will be sent in multicast,
      which will trigger energy expenditure at nearby nodes, which had
      no need for the DIOs.

   A proposed solution could be the following.  A new leaf node that