<?xml version='1.0' encoding='utf-8'?> version="1.0" encoding="UTF-8"?>

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

<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="no"?>
<?rfc subcompact="no"?>
<?rfc authorship="yes"?>
<?rfc tocappendix="yes"?>

<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 Routing Protocol for Low-Power and Lossy Networks (RPL) Destination&nbhy;Oriented Directed Acyclic Graph (DODAG) Configuration Option for the IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing&nbsp;Header</title>

<!-- [rfced] Document title: Should the abbreviated title (which appears
in the PDF in the running header) be updated as follows to more closely
match what's discussed in the text?

Original:
   Turn On 6LoRH

Perhaps:
   Turn On 6LoRH Compression

Also, we expanded the abbreviations in the full document title.
Please let us know if you prefer the "Perhaps" option below,
or otherwise.

Original:
 A RPL DODAG Configuration Option for the 6LoWPAN Routing Header</title> Header

Currently (full title):
       A Routing Protocol for Low-Power and Lossy Networks (RPL)
Destination-Oriented Directed Acyclic Graph (DODAG) Configuration Option
  for the IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN)
                             Routing Header

Perhaps (if "6LoWPAN" is not expanded):
       A Routing Protocol for Low-Power and Lossy Networks (RPL)
Destination-Oriented Directed Acyclic Graph (DODAG) Configuration Option
                   for the 6LoWPAN Routing Header
-->

   <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"/>

<!-- [rfced] Please insert any keywords (beyond those that appear in the
title) for use on https://www.rfc-editor.org/search -->

   <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>
<!-- [rfced] FYI, instances of "[RFC8138] compression"
have been rephrased as "compression per [RFC8138]" or
"6LoRH compression [RFC8138]" for the sake of clarity.
Please let us know if you prefer otherwise.
-->

    <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>
   </section>

<section><name>Terminology</name>

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

<!--
      The appendix proposes a method [rfced] Section 2.1:  Because "References" is generally used to isolate the legacy nodes that cannot be
      upgraded in a separate instance where the compression remains off.
      Upgraded nodes can participate
indicate Normative and Informative References sections in RFCs, we
changed this title to that instance "Related Documents" per RFC 8505 and as routers but will prefer
      an upgraded instance for their own traffic, so they can use the compression. was
done in RFC 9010.  Please let us know any objections.

Original:
 2.1.  References

Currently:
 2.1.  Related Documents -->

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

<section><name>Terminology</name>

<section anchor='lo'><name>References</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>MOP:</dt><dd> RPL Mode of Operation </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>SubDAG:</dt><dd> A DODAG rooted at a node, which is a child of that node and a subset of a larger DAG</dd>

<!-- [rfced] Section 2.2:  We had trouble following the use of
"which" in this definition.  We updated as noted below.  If this is
incorrect, please clarify the text.

Original:
 SubDAG:  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

Currently:
 SubDAG:  A DODAG rooted at a node, which is a child 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>RUL:</dt><dd> RPL-Unaware Leaf</dd>
    <dt>SRH:</dt><dd>Source Routing Header</dd> that node and
    a subset of a larger DAG -->

    </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='RFC2119'/><xref target='RFC8174'/> 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 DODAG Configuration option was originally
   designed with four bit positions reserved for future use as Flags.

<!-- [rfced] Section 3 and Figure 1:  The "<- Flags ->" portion of
Figure 1 appears to encompass five bit positions (0, 1, 2, 3, and 4,
where 'T' is the third position and 'A' is the fifth) instead of four.
So, should "four bit positions" be changed to "five bit positions"?

Also, please compare with Figure 5 in RFC 9010 (which shows "4 bits"),
and let us know if any changes are needed in this document.

Original (best viewed with a fixed-point font such as Courier):
 As shown in Figure 1, the Option was originally designed with
 4 bit positions reserved for future use as 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>
</figure>

      <t>
   This specification defines a new flag "Enable RFC8138 Compression" (T).
   The "T" flag is set to turn-on the use of
   <xref target='RFC8138'/> within the DODAG. The "T"

          Figure 1: DODAG Configuration Option (Partial View)
-->

   </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>
</figure>

      <t>
<!-- [rfced] This document and the IANA registry
(https://www.iana.org/assignments/rpl/rpl.xhtml#dodag-config-option-flags)
don't match for this description. Which one should be used?

This document:
   Enable RFC8138 Compression (T)

IANA registry:
   Turn on RFC8138 Compression (T)

Also, may this description be rephrased to avoid using the
RFC number as an adjective?  If so, we will send a request to
IANA to update the registry accordingly.

Perhaps:
   Turn on Compression per RFC 8138 (T)

Or:
   Turn on 6LoRH Compression (T)
-->

   This specification defines a new flag, "Enable RFC8138 Compression" (T).

<!-- [rfced] FYI, we have changed from "T" flag (double quotes) to
'T' flag (single quotes) in keeping with usage in Section 6.2 of RFC 9010.
Please let us know if you prefer otherwise.
-->

   The 'T' flag is set to turn on the use of
   <xref target='RFC8138'/> within the DODAG. The 'T' flag is encoded
   in position 2 of the reserved 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"/>
 updates
   <xref target='RFC6550'/> to indicate that the definition of the Flags applies to Mode of Operation (MOP) values zero (0) to six (6) only.

<!-- [rfced] Section 3:  Because Section 4.3 of RFC 9008 is
"Updates to RFC 8138: Indicating the Way to Decompress with the New
RPI Option Type", whereas Section 4.1 of is "Updates to RFC 6550",
we changed "4.3" to "4.1" accordingly.  Please let us know if this
is not accurate.

Original:
 Section 4.3 of [USEofRPLinfo] updates [RFC6550] to indicate that the
 definition of the Flags applies to Mode of Operation (MOP) values
 zero (0) to six (6) only.

Currently:
 Section 4.1 of [RFC9008] updates [RFC6550] to indicate that the
 definition of the 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 <bcp14>MUST</bcp14> leave the encapsulated packet as is.
   </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 router MUST <bcp14>MUST</bcp14> uncompress a packet that is to be forwarded to an external
   target. Otherwise, the router MUST <bcp14>MUST</bcp14> forward the 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'/> off in the network, the
   network administrator <bcp14>MUST</bcp14> wait until all nodes have converged to the
   'T' flag unset before allowing nodes that do not support compression in
   the network. To that effect, whether compression is active in a node
   <bcp14>SHOULD</bcp14> be exposed the node's management interface.
  </t>

<!-- [rfced] Section 5.3:  We had trouble following the first
sentence in this paragraph, and the second sentence does not parse.
If the suggested text is not correct, please clarify "converged to
the 'T' flag unset" and "SHOULD be exposed the node's management
interface".

Original:
 When turning [RFC8138] compression off in the network, the Network
 Administrator MUST wait until all nodes have converged to the "T"
 flag unset before allowing nodes that do not support the compression
 in the network.  To that effect, whether the compression is active in
 a node SHOULD be exposed the node's management interface.
  </t>

   <t>
   Nodes

Perhaps:
 When turning 6LoRH compression [RFC8138] off in the network, the network
 administrator MUST wait until all nodes have converged to the point
 where their 'T' flags are unset before allowing nodes that do not
 support <xref target='RFC8138'/> compression in the network.  Information regarding whether
 compression is active in a node SHOULD NOT be deployed visible to the node's
 management interface.

Or:
 When turning 6LoRH compression [RFC8138] off in a the network, the network where
 administrator MUST wait until each node has its 'T' flag unset before
 allowing nodes that do not support compression in the network. Information
 regarding whether compression is turned on. If that is active in a node SHOULD be exposed in the
 node's management interface.
-->

   <t>
   Nodes that do not support <xref target='RFC8138'/> <bcp14>SHOULD NOT</bcp14> be deployed
   in a network where 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
      <tr><td>2</td><td>Turn on RFC8138 Compression (T)</td><td>THIS RFC</td></tr> (T)</td><td>RFC 9035</td></tr>
   </tbody>
   </table>

<t>IANA has added this document as a reference for MOP 7 in the RPL "Mode of Operation" registry.

<!-- [rfced] This sentence appears in the original:
   IANA is requested to add [this document] as a reference for MOP 7 in
   the RPL Mode of Operation registry.
</t>

    <!--t>
    The DODAG Configuration Option Flags defined so far will be obsolete

However, the IANA registry (https://www.iana.org/assignments/rpl/rpl.xhtml#mop)
doesn't include this document as a reference for
    RPL Mode value 7:

7   Reserved   [RFC9008][RFC9010]

So, should the sentence be removed, or should the registry be updated?
(See also Section 11.3 of Operation (MOP) above RFC 9008, and including 7.
    </t>
    <t>
    IANA is requested to update the name Section 12.3 of the Registry from "DODAG Configuration Option Flags" to "DODAG Configuration Option Flags for RPL MOP 0..6".
    </t>
    <t>
    When RFC 9010.)

Also, please review whether this sentence in Section 3 is accurate.
  "For a MOP values value of 7 7, [RFC8138] MUST be
   used on links where 6LoWPAN Header Compression [RFC6282] applies and more are defined, a new registry will
   MUST NOT be needed.
    </t--> used otherwise."
-->
</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
 </t>
    <t>
    Setting the 'T' flag before all routers are upgraded may cause a loss
    of all, it packets. The new bit is worth noting that with <xref target='RFC6550'/>, every
   node in protected as the LLN that is RPL-aware can inject any RPL-based attack in rest of the
   network.

   A trust model configuration, so
    this is REQUIRED in just one of the many attacks that can happen if an effort to exclude rogue nodes from
   participating attacker manages
    to the RPL and the 6LoWPAN signaling, as well inject a corrupted configuration.

<!-- [rfced] Section 7:  We had trouble following this sentence; are
some words missing?  Please clarify "is protected as from the data
   packet exchange.  This trust model could at a minimum be based on a Layer-2
   Secure joining and rest of the Link-Layer security. This
configuration".

Original (the previous sentence is a generic RPL and 6LoWPAN
   requirement, see Req5.1 in Appendix of <xref target='RFC8505'/>.
   -->
 </t>
    <t> included for context):
 Setting the "T" 'T' flag before all routers are upgraded may cause a loss
 of packets.  The new bit is protected as the rest of the
 configuration so this is just one of the many attacks that can happen
 if an attacker manages to inject a corrupted configuration. -->

    </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
    Conversely, it may set the "T" flag, 'T' flag so
    that nodes located downstream would compress when that it is not desired,
    potentially resulting in the loss of packets. 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 above would be more complex and more visible than
    simply dropping selected packets. The downstream node may have other
    parents and see 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 and responsive
   when need comes.
   </t>
   </section><!-- ack -->
</middle>

<back>

   <displayreference   target="I-D.ietf-roll-useofrplinfo"     to="USEofRPLinfo"/>
   <displayreference   target="I-D.ietf-roll-unaware-leaves"     to="UNAWARE-LEAVES"/>
    <references><name>Normative References</name>
	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml'/> <!-- BCP14 -->
	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml'/> <!-- BCP14 -->
	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6550.xml'/> <!-- RPL -->
  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7102.xml'/> <!-- RPI -->
  	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8138.xml'/> <!-- 6LoRH for RPL artifacts -->

  	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8505.xml'/>
      <!--6LoWPAN ND -->     <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-roll-unaware-leaves.xml'/>

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

	  <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7416.xml'/> <!-- Security Threat Analysis for RPL -->

      <xi:include href='https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-roll-useofrplinfo.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 [rfced] Section 7:  We had trouble following this paragraph.
If the suggested text is not correct, please clarify "would compress
when that it does is not support desired" and "both settings, which could raise
attention".

Original:
 An attacker may unset the Mode of Operation "T" flag to force additional energy
 consumption of a RPL Instance, the Objective Function
   (OF) as indicated by the Objective Code Point (OCP) child or some other parameters descendant nodes in its subDAG.  Conversely
 it may set the configuration option.
   </t>

   <t>
   This specification reiterates that a RAN that is configured 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 "T" flag, so that a legacy RAN will not recognize nodes located downstream would
 compress when a
   reserved field that it is used and will not turn to a leaf when the "T" flag is set.
   </t>

   <t>
   The two RPL Instances operate independently as specified desired, potentially resulting in <xref target='RFC6550'/>.  The preexisting RPL Instance does not use
   <xref target='RFC8138'/>, whereas the new RPL Instance does. This is signaled
   by
 loss of packets.  In a tree structure, the "T" flag which is only set attacker would be in
 position to drop the configuration option in DIO messages
   in packets from and to the new RPL Instance.
   </t>

   <t>
   Nodes that support <xref target='RFC8138'/> participate in attacked nodes.  So the
 attacks above would be more complex and more visible than simply
 dropping selected packets.  The downstream node may have other
 parents and see both Instances but
   favor settings, which could raise attention.

Suggested:
 An attacker may unset the new RPL Instance for 'T' flag to force additional energy
 consumption of child or descendant nodes in its subDAG.  Conversely,
 it may set the traffic 'T' flag so that they source.
   By contrast, nodes that only support the uncompressed format located downstream would
   either
 compress packets even when compression is not be configured for desired, potentially
 causing packet loss.  In a tree structure, the new RPL Instance, or attacker would be configured to
   join it as leaves only.
   </t>

   <t>
   This method requires implementations in
 a position to support at least two RPL
   Instances drop the packets from and demands management capabilities to introduce new RPL Instances the attacked nodes.  So,
 the attacks mentioned above would be more complex and deprecate old ones.
   </t>

   <t> more visible
 than simply dropping selected packets.  The 2 instances MUST be operated with the same security guarantees, e.g., downstream node may have
 other parents and see both "unsecured" with a lower layer security of settings; such a same strength, both
   "preinstalled" or both "authenticated" security mode (see section 3.2.3 of
   <xref target='RFC6550'/> for more details on those modes). The latter mode scenario could be use raise
 concerns. -->

    </t>
   </section>
</middle>

<back>
   <references><name>References</name>

    <references><name>Normative References</name>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6550.xml'/>
  <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7102.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8138.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8505.xml'/>

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

   </references>
   <references><name>Informative References</name>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6282.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6553.xml'/>
  <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7228.xml'/>
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7416.xml'/>

<!-- draft-ietf-roll-useofrplinfo (RFC 9008) -->
          <xi:include href='https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9008.xml'/>
   </references>
   </references>

   <section numbered="false"><name>Acknowledgments</name>
   <t>
   The authors wish to enforce the segregation of updated 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 non-updated nodes, by
   providing the keys especially <contact fullname="Benjamin Kaduk"/>, <contact fullname="Alvaro Retana"/>, <contact fullname="Dominique Barthel"/>,
   and <contact fullname="Rahul Jadhav"/> for joining as routers their in-depth reviews and constructive suggestions.
   </t><t>
   Also, many thanks to <contact fullname="Michael Richardson"/> for always being  helpful and responsive when the updated nodes only. need arises.
   </t>
   </section>

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