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<!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent">

<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
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<rfc  xmlns:xi="http://www.w3.org/2001/XInclude" category="std" ipr='trust200902' tocInclude="true"  sortRefs="true" symRefs="true" obsoletes="" updates="8138" consensus="true" submissionType="IETF"  category="std" consensus="true" xml:lang="en" version="3" docName="draft-ietf-roll-turnon-rfc8138-18">  docName="draft-ietf-roll-turnon-rfc8138-18" number="9035" version="3">

<front>
   <title abbrev='Turn On 6LoRH'>A RPL DODAG 6LoRH Compression'>A Routing Protocol for Low-Power and Lossy Networks (RPL) Destination&nbhy;Oriented Directed Acyclic Graph (DODAG) Configuration Option for the 6LoWPAN Routing Header</title>
   <seriesInfo name="RFC" value="9035"/>

   <author fullname='Pascal Thubert' initials='P.' role='editor' surname='Thubert'>
      <organization abbrev='Cisco Systems'>Cisco Systems, Inc</organization> Inc.</organization>
      <address>
         <postal>
            <street>Building D</street>
           <extaddr>Building D</extaddr>
            <street>45 Allee des Ormes - BP1200 </street>
            <city>MOUGINS - Sophia Antipolis</city>
            <code>06254</code>
            <country>FRANCE</country>
            <country>France</country>
         </postal>
         <phone>+33 497 23 26 34</phone>
         <email>pthubert@cisco.com</email>
      </address>
   </author>

          <author initials='L' surname='Zhao' fullname='Li Zhao'>
          <organization abbrev='Cisco Systems'>Cisco Systems, Inc</organization> Inc.</organization>
          <address>
             <postal>
                <street>Xinsi Building</street>
               <extaddr>Xinsi Building</extaddr>
                <street>No. 926 Yi Shan Rd </street>
                <city>SHANGHAI </city> Rd</street>
                <city>Shanghai</city>
                <code>200233</code>
                <country>CHINA</country>
                <country>China</country>
             </postal>
             <email>liz3@cisco.com</email>
          </address>
       </author>

   <date/>
   <area>Routing Area</area>
   <workgroup>ROLL</workgroup>
   <keyword>Draft</keyword>

       <date year="2021" month="April"/>

<keyword>IoT</keyword>
<keyword>Header Compression</keyword>
<keyword>Source Routing Header</keyword>
<keyword>Hop-by-Hop Header</keyword>
<keyword>RPL artifacts</keyword>

   <abstract>
      <t>
     This document updates RFC 8138 by defining a bit in the RPL DODAG Routing Protocol for Low-Power and Lossy Networks (RPL) Destination-Oriented Directed Acyclic Graph (DODAG)
     Configuration Option option to indicate whether compression is used within the
     RPL Instance, Instance and to specify the behavior of RFC 8138-capable nodes compliant with RFC 8138
     when the bit is set and unset.
      </t>
   </abstract>
</front>

<middle>
   <section><name>Introduction</name>

    <t>
    The design of Low Power Low-Power and Lossy Networks (LLNs) is generally focused on
    saving energy, which is the most constrained resource of all. The routing
    optimizations in the "<xref target="RFC6550" format="title"/>" <xref target='RFC6550'>"Routing Protocol for Low Power
    and Lossy Networks"</xref> (RPL) target="RFC6550" format="default"/>, such as routing along a
    Destination-Oriented Directed Acyclic Graph (DODAG) to a Root Node and the
    associated routing header compression and forwarding technique specified in
    <xref target='RFC8138'/> target='RFC8138'/>, derive from that primary concern.
    </t>
    <t>
    Enabling <xref target='RFC8138'/> on a running network requires a Flag Day "flag day",
    where the network is upgraded and rebooted.
    Otherwise, if acting as a Leaf, leaf, a node that does not
    support the compression per <xref target='RFC8138'/> would fail to communicate; if acting as a router router, it
    would drop the compressed packets and black-hole a portion of the network.
    This specification enables a hot upgrade where a live network is migrated. During the migration, the compression remains inactive, inactive until all nodes are upgraded.
      </t>
      <t>
    This document complements <xref target='RFC8138'/> and signals whether it
    should be used within a RPL DODAG with a new flag in the RPL DODAG
    Configuration Option. option.
    The setting of this new flag is controlled by the Root and propagates as
    is in the whole network as part of the normal RPL signaling.
      </t>
      <t>
      The flag is cleared to maintain the ensure that compression remains inactive during
      the migration phase. When the migration is complete (e.g., as known by
      network management and/or inventory), the flag is set and the compression
      is globally activated in the whole DODAG.
      </t>
      <!--
      The appendix proposes a method to isolate the legacy nodes that cannot be
      upgraded in a separate instance where the compression remains off.
      Upgraded nodes can participate to that instance as routers but will prefer
      an upgraded instance for their own traffic, so they can use the compression.
       -->

   </section><!-- title="Introduction"-->
   </section>

<section><name>Terminology</name>

<section anchor='lo'><name>References</name> anchor='lo'><name>Related Documents</name>

<t>
   The terminology used in this document is consistent with with, and incorporates
   that described in
   the terms provided in, "<xref target="RFC7102" format="title"/>" <xref target='RFC7102'>"Terms Used in Routing for Low-Power
   and Lossy Networks (LLNs)"</xref>. target="RFC7102" format="default"/>.
   Other terms in use in as related to LLNs are found in "<xref target="RFC7228" format="title"/>" <xref target='RFC7228'>
   "Terminology for Constrained-Node Networks"</xref>. target="RFC7228" format="default"/>.
</t>

<t>"RPL", the "RPL Packet Information" (RPI), and "RPL Instance" (indexed by a
   RPLInstanceID) are defined in "<xref target="RFC6550" format="title"/>" <xref target='RFC6550'>"RPL: IPv6 Routing
   Protocol for Low-Power and Lossy Networks"</xref>. target="RFC6550" format="default"/>.
 The RPI is the abstract
   information that RPL defines to be placed in data packets, e.g., as the RPL
   Option <xref target='RFC6553'/> within the IPv6 Hop-By-Hop Header.
   By extension extension, the term "RPI" is often used to refer to the RPL Option itself.
   The DODAG Information Solicitation (DIS), Destination Advertisement Object
   (DAO)
   (DAO), and DODAG Information Object (DIO) messages are also specified in
   <xref target='RFC6550'/>.
</t><t>

   This document uses the terms RPL-Unaware Leaf "RPL-Unaware Leaf" (RUL) and RPL-Aware Leaf "RPL-Aware Leaf"
   (RAL) consistently with <xref target='I-D.ietf-roll-useofrplinfo'> target='RFC9008'> "Using RPI Option Type, Routing Header for Source Routes Routes, and IPv6-in-IPv6 encapsulation Encapsulation in the RPL Data Plane"</xref>.
   The term RPL-Aware Node "RPL-Aware Node" (RAN) refers to a node that is either
   a RAL or a RPL Router. router. A RAN manages the reachability of its addresses and
   prefixes by injecting them in RPL by itself. In contrast, a RUL leverages
   "<xref target="RFC8505" format="title"/>" <xref target='RFC8505'>"Registration Extensions for IPv6 over
    Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery"
    </xref> target="RFC8505" format="default"/>
   to obtain reachability services from its parent router(s)
    as specified in <xref target='I-D.ietf-roll-unaware-leaves'> target='RFC9010'> "Routing for RPL (Routing Protocol for Low-Power and Lossy Networks) Leaves"</xref>.
</t>

</section>	<!-- end section "References" -->
<section anchor='gloss'><name>Glossary</name>
 <t> This document often uses the following acronyms: abbreviations:
    </t>
    <dl spacing='compact'>
    <dt>6LoRH:</dt><dd>6LoWPAN Routing Header</dd>
    <dt>6LoWPAN:</dt><dd>IPv6 over Low-Power Wireless Personal Area Network</dd>
    <dt>6LoRH:</dt><dd>6LoWPAN Routing Header</dd>
    <dt>DIO:</dt><dd> DODAG Information Object (a RPL message) </dd>
    <dt>DODAG:</dt><dd> Destination-Oriented Directed Acyclic Graph </dd>
    <dt>LLN:</dt><dd> Low-Power and Lossy Network </dd>
    <dt>RPL:</dt><dd> IPv6 Routing Protocol for Low-Power and Lossy Networks </dd>
    <dt>SubDAG:</dt><dd> A DODAG rooted at a node which is a child of that node and a subset of a larger DAG </dd>
    <dt>MOP:</dt><dd> RPL Mode of Operation </dd>
    <dt>RPI:</dt><dd> RPL Packet Information </dd>
    <dt>RAL:</dt><dd> RPL-Aware Leaf </dd>
    <dt>RAN:</dt><dd> RPL-Aware Node  </dd>
    <dt>RPI:</dt><dd> RPL Packet Information </dd>
    <dt>RPL:</dt><dd> IPv6 Routing Protocol for Low-Power and Lossy Networks </dd>
    <dt>RUL:</dt><dd> RPL-Unaware Leaf</dd>
    <dt>SRH:</dt><dd>Source Routing Header</dd>
    <dt>Sub-DODAG:</dt><dd>The sub-DODAG of a node is a DODAG rooted at that node that is a subset of a main DODAG the node belongs to. It is formed by the other nodes in the
main DODAG whose paths to the main DODAG root pass through that node.</dd>
    </dl>
</section>	<!-- end section "Glossary" -->

<section anchor='bcp'><name>Requirements Language</name>
<t>

    The
       <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
       "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>",
       "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>",
       "<bcp14>SHOULD NOT</bcp14>",
       "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
       "<bcp14>MAY</bcp14>", and
    "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document
       are to be interpreted as described in BCP 14 BCP&nbsp;14
       <xref target='RFC2119'/><xref target='RFC8174'/> target="RFC2119"/> <xref target="RFC8174"/> when, and only
       when, they appear in all capitals, as shown here.

</t> here.</t>
</section>	<!-- end section "Requirements Language" -->

</section>	<!-- end section "Terminology" -->

   <section><name>Extending RFC 6550</name>
   <t>
   The DODAG Configuration Option option is defined in Section 6.7.6 of <xref target=
   'RFC6550'/>. target="RFC6550" sectionFormat="of" section="6.7.6"/>. Its purpose is extended to distribute configuration
   information affecting the construction and maintenance of the DODAG, as
   well as operational parameters for RPL on the DODAG, through the DODAG.

   As shown in <xref target="RPLDCO"/>, the Option

   The DODAG Configuration option was originally
   designed with 4 four bit positions reserved for future use as Flags. flags.
   </t>

<figure anchor="RPLDCO">
          <name>DODAG Configuration Option (Partial View) </name>
       <artwork align="center" name="" type="" alt=""><![CDATA[
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Type = 0x04 |Opt Length = 14| | |T| |A|       ...           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                     +
                                <- Flags ->
]]></artwork> flags ->]]></artwork>
</figure>

      <t>
   This specification defines a new flag flag, "Enable RFC8138 Compression" (T). Compression per RFC 8138 (T)".
   The "T" 'T' flag is set to turn-on turn on the use of
   <xref target='RFC8138'/> within the DODAG. The "T" 'T' flag is encoded
   in position 2 of the reserved Flags flags in the DODAG Configuration Option option (counting from bit 0 as the most significant bit) and set to 0 in
   legacy implementations as specified respectively in Sections 20.14
Sections&nbsp;<xref target="RFC6550" section="20.14"
 sectionFormat="bare"/> and 6.7.6 <xref target="RFC6550" section="6.7.6"
 sectionFormat="bare"/> of <xref target='RFC6550'/>. target="RFC6550"/>, respectively.
   </t>
   <t>
   Section 4.3 of
   <xref target='I-D.ietf-roll-useofrplinfo'/> target="RFC9008" sectionFormat="of" section="4.1.2"/>
 updates
   <xref target='RFC6550'/> to indicate that the definition of the Flags flags applies to Mode of Operation (MOP) values zero (0) to six (6) only.
   For a MOP value of 7, <xref target='RFC8138'/> MUST <bcp14>MUST</bcp14> be used on Links links where 6LoWPAN Header
   Compression <xref target='RFC6282'/> applies and MUST NOT <bcp14>MUST NOT</bcp14> be used otherwise.

   </t>
      <t>
   The RPL DODAG Configuration Option option is typically placed in
   a DODAG Information Object (DIO) DIO message. The DIO message propagates down the
   DODAG to form and then maintain its structure. The DODAG Configuration Option option
   is copied unmodified from parents to children.

<!-- Quoted text is DNE.  Verified.  Fixed per RFC 6550. -->
   <xref target='RFC6550'/> states that "Nodes other than the DODAG Root MUST
   NOT root
   <bcp14>MUST NOT</bcp14> modify this information when propagating the DODAG Configuration option". option."
   Therefore, a legacy parent propagates the "T" 'T' flag as set by the Root, and
   when the "T" 'T' flag is set, it is transparently flooded to all the nodes in the DODAG.
  </t>
   </section><!-- Updating RFC 6550 was: The RPL DODAG Configuration Option -->
   </section>

   <section><name>Updating RFC 8138</name>

   <t>
   A node SHOULD <bcp14>SHOULD</bcp14> generate packets in the compressed form using
   <xref target='RFC8138'/> if and only if the "T" 'T' flag
   is set. This behavior can be overridden by configuration or network
   management. Overriding may be needed needed, e.g., to turn on the compression in a
   network where all nodes support <xref target='RFC8138'/> but the Root does
   not support this specification and cannot set the "T" 'T' flag, or to disable it
   locally in case of a problem.
   </t>
   <t>
   The decision to use <xref target='RFC8138'/> is made by the originator of
   the packet packet, depending on its capabilities and its knowledge of the state of
   the "T" 'T' flag.
   A router encapsulating a packet is the originator of the resulting
   packet and is responsible for compressing the outer headers with per
   <xref target= 'RFC8138'/>, but it MUST leave <bcp14>MUST NOT</bcp14> perform compression on the encapsulated packet as is. packet.
   </t>
   <t>
   An external target <xref target='I-D.ietf-roll-useofrplinfo'/> target='RFC9008'/> is not
   expected to support <xref target='RFC8138'/>. In most cases, packets to and
   from an external target are tunneled back and forth between the border router
   (referred to as 6LR) a 6LoWPAN Router (6LR)) that serves the external target and the Root, regardless
   of the MOP used in the RPL DODAG.
   The inner packet is typically not compressed with per <xref target='RFC8138'/>,
   so for outgoing packets, the border router just needs to decapsulate the
   (compressed) outer header and forward the (uncompressed) inner packet towards
   the external target.
   </t>
   <t>
   A border router MUST uncompress that forwards a packet that is to be forwarded to an external
   target. Otherwise, target <bcp14>MUST</bcp14>
   uncompress the packet first. In all other cases, a router MUST <bcp14>MUST</bcp14>
   forward the a packet in the form that the source used, either compressed or
   uncompressed.
   </t>
   <t>
   A RUL <xref target='I-D.ietf-roll-unaware-leaves'/> target='RFC9010'/> is both a leaf and an
   external target. A RUL does not participate in RPL and
   depends on the parent router to obtain connectivity. In the case of a RUL,
   forwarding towards an external target actually means delivering the packet.
   </t>

   </section><!-- Updating RFC 8138 -->

   </section>

   <section><name>Transition Scenarios</name>
   <t>
   A node that supports <xref target='RFC8138'/> but not this specification
   can only be used in a homogeneous network.
   Enabling the compression per <xref target='RFC8138'/> compression without a turn-on signaling
   method requires a "flag day"; flag day, by which time all nodes must be upgraded, upgraded and
   at which point the network can be rebooted with the 6LoRH compression <xref target='RFC8138'/>
   compression turned on.
   </t>
   <t>
   The intent for of this specification is to perform a migration once and for all all,
   without the need for a flag day. In particular it particular, the intent is not the intention to
   undo the setting of the "T" 'T' flag.
   Though it is possible to roll back (see <xref target='rb'/>), the roll back rollback
   operation SHOULD <bcp14>SHOULD</bcp14> be complete before the network operator adds nodes
   that do not support <xref target='RFC8138'/>.
   </t>

   <section anchor='coex'><name>Coexistence</name>
   <t>
    A node that supports this specification can operate in a network with the 6LoRH
    compression <xref target='RFC8138'/> compression turned on or off with the "T" 'T' flag set
    accordingly and in a network in transition from off to on or on to off
    (see <xref target='mig'/>).
   </t>
   <t>
    A node that does not support <xref target='RFC8138'/> can interoperate with
    nodes that do in a network with 6LoRH compression <xref target='RFC8138'/> compression turned
    off. If the compression is turned on, all the RPL-Aware Nodes RANs are expected
    to be able to handle compressed packets in the compressed form. A node that
    cannot do so may remain connected to the network as a RUL as described in
    <xref target='I-D.ietf-roll-unaware-leaves'/>. target='RFC9010'/>.
   </t>

   </section><!--Coexistence-->

   </section>

   <section anchor='mig'><name>Inconsistent State While Migrating</name>

   <t>
   When the "T" 'T' flag is turned on by the Root, the
   information slowly percolates through the DODAG as the DIO gets propagated.
   Some nodes will see the flag and start sourcing packets in the compressed
   form
   form, while other nodes in the same RPL DODAG are will still not be aware of it.
   In non-storing Non-Storing mode, the Root will start using
   <xref target='RFC8138'/> with a Source Routing Header 6LoRH (SRH-6LoRH)
   that routes all the way to the parent router or to the leaf.
   </t>

   <t>
   To ensure that a packet is forwarded across the RPL DODAG in the form in
   which it was generated, it is required that all the RPL nodes support
   <xref target='RFC8138'/> at the time of the switch.
   </t>

   <t>
   Setting the "T" 'T' flag is ultimately the responsibility of the Network
   Administrator. network
   administrator. The expectation is that the network management or upgrading
   tools in place enable the Network Administrator network administrator to know when all the nodes
   that may join a DODAG were migrated. In the case of a RPL instance Instance with
   multiple Roots, all nodes that participate to in the RPL Instance may
   potentially join any DODAG.
   The network MUST <bcp14>MUST</bcp14> be operated with the "T" 'T' flag unset until all nodes in the
   RPL Instance are upgraded to support this specification.
   </t>

   </section> <!--"Transient State while migrating"-->

   <section anchor='rb'><name>Rolling Back</name>

  <t>
   When turning 6LoRH compression <xref target='RFC8138'/> compression off in the network, the
   Network Administrator MUST
   network administrator <bcp14>MUST</bcp14> wait until all nodes have converged to the
   "T" each node has its 'T' flag
   unset before allowing nodes that do not support the compression in
   the network. To that effect, Information regarding whether the compression is active in a node
   SHOULD
   <bcp14>SHOULD</bcp14> be exposed in the node's management interface.
  </t>
   <t>
   Nodes that do not support <xref target='RFC8138'/> SHOULD NOT <bcp14>SHOULD NOT</bcp14> be deployed
   in a network where the compression is turned on. If that is done, the node
   can only operate as a RUL.
   </t>

   </section> <!-- Rolling Back -->

   </section> <!-- Transition Scenarios -->

   <section anchor="iana"><name>IANA Considerations</name>
       <t>
    This specification updates the Registry that was created for <xref target='RFC6550'/> as the registry for "DODAG Configuration Option Flags" and updated as the registry for "DODAG Configuration Option Flags for MOP
0..6" by registry <xref target='I-D.ietf-roll-useofrplinfo'/>, by allocating one
    new Flag as follows:
<!--
    IANA is requested to assign a new option flag from the Registry for target='RFC9008'/> (formerly the "DODAG Configuration Option Flags" that registry, which was created for <xref target='RFC6550'/>  and updated as the registry for "DODAG Configuration Option Flags for MOP 0..6" target='RFC6550'/>), by <xref target='I-D.ietf-roll-useofrplinfo'/>as allocating one
 new flag as follows:
 -->
    </t>

   <table  anchor="nexndopt"><name>New DODAG Configuration Option Flag</name>
   <thead>
      <tr><td>Bit Number</td><td>Capability Description</td><td>Reference</td></tr>
   </thead><tbody>

   <!--

   Note to IANA:
   if the bit position is changed, then fig 1 and the text below are impacted
   and should be modified accordingly

   -->
      <tr><td>2 (suggested)</td><td>Turn on RFC8138
      <tr><td>2</td><td>Enable Compression (T)</td><td>THIS RFC</td></tr> per RFC 8138 (T)</td><td>RFC 9035</td></tr>
   </tbody>
   </table>

<t>IANA is requested to add [this document] has added this document as a reference for MOP 7 in the RPL Mode "Mode of Operation Operation" registry.
</t>

    <!--t>
    The DODAG Configuration Option Flags defined so far will be obsolete for
    RPL Mode of Operation (MOP) above and including 7.
    </t>
    <t>
    IANA is requested to update the name of the Registry from "DODAG Configuration Option Flags" to "DODAG Configuration Option Flags for RPL MOP 0..6".
    </t>
    <t>
    When MOP values of 7 and more are defined, a new registry will be needed.
    </t-->
   </section>

   <section anchor='sec'><name>Security Considerations</name>
    <t>
   It is worth noting that in RPL <xref target='RFC6550'/>, every node in the
   LLN that is RPL-aware RPL aware and has access to the RPL domain can inject any RPL-based attack in the network, more in network; see <xref target='RFC7416'/>. target='RFC7416'/> for details.
   This document applies typically applies to an existing deployment and does not change
   its security requirements and operations.
   It is assumed that the security mechanisms as defined for RPL are followed.

<!--
   First of all, it is worth noting that with <xref target='RFC6550'/>, every
   node in the LLN that is RPL-aware can inject any RPL-based attack in the
   network.

   A trust model is REQUIRED in an effort to exclude rogue nodes from
   participating to the RPL and the 6LoWPAN signaling, as well as from the data
   packet exchange.  This trust model could at a minimum be based on a Layer-2
   Secure joining and the Link-Layer security. This is a generic RPL and 6LoWPAN
   requirement, see Req5.1 in Appendix of <xref target='RFC8505'/>.
   -->
 </t>
    <t>
    Setting the "T" 'T' flag before all routers are upgraded may cause a loss
    of packets. The new bit is protected benefits from the same protection as the rest of the configuration so
    this
    information in the DODAG Configuration option that transports it. Touching
    the new bit is just one of the many attacks that can happen if an
    attacker manages to inject a corrupted configuration. configuration option in the network.
    </t><t>
    Setting and unsetting the "T" 'T' flag may create inconsistencies in the network network,
    but as long as all nodes are upgraded to <xref target='RFC8138'/> provide support for <xref target='RFC8138'/>,
    they will be able to forward both forms. The source is responsible
    for selecting whether the packet is compressed or not, and all routers must
    use the format that the source selected. So So, the result of an inconsistency
    is merely that both forms will be present in the network, at an additional
    cost of bandwidth for packets in the uncompressed form.

    </t><t>
    An attacker may unset the "T" 'T' flag to force additional energy consumption of child or descendant nodes in its subDAG.
    Conversely sub-DODAG.
    Conversely, it may set the "T" flag, 'T' flag so
    that nodes located downstream would compress packets even when that it compression is not desired, potentially resulting in the loss of packets. causing packet loss.  In a tree structure, the attacker would be in a position to drop the packets from and to the attacked nodes. So  So, the attacks mentioned above would be more complex and more visible than simply dropping selected packets.  The downstream node may have other parents and see the bit with both settings, which could raise attention.
    </t>
   </section>

   <section><name>Acknowledgments</name>
   <t>
   The authors wish to thank
   Murray Kucherawy, Meral Shirazipour, Barry Leiba, Tirumaleswar Reddy,
   Nagendra Kumar Nainar, Stewart Bryant, Carles Gomez, Eric Vyncke,
   Roman Danyliw,
   and especially Benjamin Kaduk, Alvaro Retana, Dominique Barthel
   and Rahul Jadhav for their in-depth reviews and constructive suggestions.
   </t><t>
   Also many thanks to Michael Richardson for being always helpful
settings; such a situation may be detected, and responsive
   when need comes. an alert may be triggered.
    </t>
   </section><!-- ack -->
   </section>
</middle>

<back>

   <displayreference   target="I-D.ietf-roll-useofrplinfo"     to="USEofRPLinfo"/>
   <displayreference   target="I-D.ietf-roll-unaware-leaves"     to="UNAWARE-LEAVES"/>
   <references><name>References</name>

    <references><name>Normative References</name>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml'/> <!-- BCP14 --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml'/> <!-- BCP14 --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6550.xml'/> <!-- RPL --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6550.xml'/>
  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7102.xml'/> <!-- RPI --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7102.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8138.xml'/> <!-- 6LoRH for RPL artifacts --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8138.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8505.xml'/>
      <!--6LoWPAN ND href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8505.xml'/>

<!-- draft-ietf-roll-unaware-leaves (RFC 9010) -->
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-roll-unaware-leaves.xml'/> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9010.xml'/>

   </references>
   <references><name>Informative References</name>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6282.xml'/> <!-- 6lowpan HC --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6282.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6553.xml'/> <!-- RPI --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6553.xml'/>
  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7228.xml'/> <!-- termonology --> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7228.xml'/>
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7416.xml'/> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7416.xml'/>

<!-- Security Threat Analysis for RPL draft-ietf-roll-useofrplinfo (RFC 9008) -->
          <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-roll-useofrplinfo.xml'/> href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9008.xml'/>
   </references>

   <!-- section anchor='dic'><name>Double RPL Instances Scenario</name>
   <t>
   Sections 8.5 and 9.2 of <xref target='RFC6550'/> suggests that a
   RAN may only attach to a DODAG as a leaf when it does
   not support the Mode of Operation of a RPL Instance, the Objective Function
   (OF) as indicated by the Objective Code Point (OCP) or some other parameters
   in the configuration option.
   </t>
   </references>

   <section numbered="false"><name>Acknowledgments</name>
   <t>
   This specification reiterates that a RAN that is configured
   The authors wish to operate in a
   RPL Instance but does not support a value for a known parameter that is
   mandatory for routing, such as the OCP, MUST NOT operate as a router but MAY
   still join as a leaf. Note that a legacy RAN will not recognize when a
   reserved field is used thank
   <contact fullname="Murray Kucherawy"/>, <contact fullname="Meral Shirazipour"/>, <contact fullname="Barry Leiba"/>, <contact fullname="Tirumaleswar Reddy"/>,
   <contact fullname="Nagendra Kumar Nainar"/>, <contact fullname="Stewart Bryant"/>, <contact fullname="Carles Gomez"/>, <contact fullname="Éric Vyncke"/>,
   <contact fullname="Roman Danyliw"/>,
   and will not turn to a leaf when the "T" flag is set.
   </t>

   <t>
   The two RPL Instances operate independently as specified
   in <xref target='RFC6550'/>.  The preexisting RPL Instance does not use
   <xref target='RFC8138'/>, whereas the new RPL Instance does. This is signaled
   by the "T" flag which is only set in the configuration option in DIO messages
   in the new RPL Instance.
   </t>

   <t>
   Nodes that support <xref target='RFC8138'/> participate in both Instances but
   favor the new RPL Instance for the traffic that they source.
   By contrast, nodes that only support the uncompressed format would
   either not be configured especially <contact fullname="Benjamin Kaduk"/>, <contact fullname="Alvaro Retana"/>, <contact fullname="Dominique Barthel"/>,
   and <contact fullname="Rahul Jadhav"/> for the new RPL Instance, or would be configured to
   join it as leaves only.
   </t>

   <t>
   This method requires implementations to support at least two RPL
   Instances their in-depth reviews and demands management capabilities constructive suggestions.
   </t><t>
   Also, many thanks to introduce new RPL Instances
   and deprecate old ones.
   </t>

   <t>
   The 2 instances MUST be operated with the same security guarantees, e.g.,
   both "unsecured" with a lower layer security of a same strength, both
   "preinstalled" or both "authenticated" security mode (see section 3.2.3 of
   <xref target='RFC6550'/> <contact fullname="Michael Richardson"/> for more details on those modes). The latter mode
   could be use to enforce the segregation of updated always being  helpful and non-updated nodes, by
   providing the keys for joining as routers to responsive when the updated nodes only. need arises.
   </t>
   </section>

   Double Instance Scenario -->
</back>
</rfc>