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  <front>
    <title abbrev="PMIPv6 DMM and DLIF">Proxy Mobile IPv6 extensions Extensions for Distributed Mobility Management</title>

    <!-- AUTHORS -->
    <seriesInfo name="RFC" value="8885"/>

    <author fullname="Carlos J. Bernardos" initials="CJ." surname="Bernardos">
      <organization abbrev="UC3M">Universidad Carlos III de
      Madrid</organization>
      <address>
        <postal>
	<street>Av. Universidad, 30</street>
          <city>Leganes, Madrid</city>
	<city>Leganes</city>
          <region>Madrid</region>
          <code>28911</code>
          <country>Spain</country>
        </postal>
        <phone>+34 91624 6236</phone>
        <email>cjbc@it.uc3m.es</email>
        <uri>http://www.it.uc3m.es/cjbc/</uri>
      </address>
    </author>
    <author fullname="Antonio de la Oliva" initials="A." surname="de la Oliva">
      <organization abbrev="UC3M">Universidad Carlos III de
      Madrid</organization>
      <address>
        <postal>
          <street>Av. Universidad, 30</street>
          <city>Leganes, Madrid</city>
          <city>Leganes</city>
	<region>Madrid</region>
          <code>28911</code>
          <country>Spain</country>
        </postal>
        <phone>+34 91624 8803</phone>
        <email>aoliva@it.uc3m.es</email>
        <uri>http://www.it.uc3m.es/aoliva/</uri>
      </address>
    </author>
    <author fullname="Fabio Giust" initials="F." surname="Giust">
      <organization abbrev="Athonet">Athonet S.r.l.</organization>
      <address>
        <email>fabio.giust.2011@ieee.org</email>
<postal>
<street>via Ca' del Luogo 6/8</street>
<city>Bolzano Vicentino (VI)</city>
<code>36050</code>
<country>Italy</country>
</postal>
        <email>fabio.giust.research@gmail.com</email>
      </address>
    </author>
    <author fullname="Juan Carlos Zuniga" Zúñiga" initials="JC."
            surname="Zuniga"> surname="Zúñiga">
      <organization abbrev="SIGFOX">
        SIGFOX
      </organization>
      <address>
        <postal>
          <street>425 rue Jean Rostand</street>
          <city>Labege</city>
          <code> 31670</code>
          <country>France</country>
        </postal>
        <email>j.c.zuniga@ieee.org</email>
        <uri>http://www.sigfox.com/</uri>
      </address>
    </author>
    <author fullname="Alain Mourad" initials="A." surname="Mourad">
      <organization abbrev="InterDigital">
        InterDigital Europe
      </organization>
      <address>
        <email>Alain.Mourad@InterDigital.com</email>
        <uri>http://www.InterDigital.com/</uri>
      </address>
    </author>
    <date month="March" year="2020" /> month="October" year="2020"/>
    <area>Internet</area>
    <workgroup>DMM Working Group</workgroup>

<keyword>PMIPv6</keyword>
<keyword>anchor</keyword>
<keyword>session continuity</keyword>
<keyword>address reachability</keyword>
<keyword>HNP</keyword>
<keyword>CMD</keyword>
<keyword>MAAR</keyword>

    <abstract>
      <t>
Distributed Mobility Management solutions allow for setting up networks so to be set up
in such a way that
traffic is distributed in an optimal way optimally and does not rely on centrally
deployed anchors are not relied upon to provide IP mobility support.
      </t>

      <t>
There are many different approaches to address Distributed Mobility Management,
as Management
-- for example example, extending network-based mobility protocols (like Proxy Mobile
IPv6),
IPv6) or client-based mobility protocols (like Mobile IPv6), among others. This
document follows the former approach and proposes a solution based on Proxy
Mobile IPv6 IPv6, in which mobility sessions are anchored at the last IP hop router
(called the mobility anchor and access router). The mobility anchor and access
router is an enhanced access router which that is also able to operate as a local
mobility anchor or mobility access gateway, gateway on a per prefix per-prefix basis. The document
focuses on the required extensions to effectively support simultaneously the simultaneous
anchoring several flows at different distributed gateways.
      </t>
    </abstract>

    <note title="Requirements Language">

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

    </note>
  </front>
  <middle>
    <section anchor="sec:introduction" title="Introduction"> anchor="sec_introduction" numbered="true" toc="default">
      <name>Introduction</name>
      <t>
The Distributed Mobility Management (DMM) paradigm aims at minimizing the impact
of currently standardized mobility management solutions solutions, which are centralized
(at least to a considerable extent) <xref target="RFC7333"></xref>. target="RFC7333" format="default"/>.
      </t>
      <t>
Current
The two most relevant examples of current IP mobility solutions, standardized with the names of solutions are Mobile
IPv6 <xref
target="RFC6275"></xref>, or target="RFC6275" format="default"/> and Proxy Mobile IPv6 (PMIPv6)
<xref
target="RFC5213"></xref>, just to cite the two most relevant examples, target="RFC5213" format="default"/>. These solutions offer
mobility support at the cost of handling operations at a cardinal point, the
mobility anchor point (i.e.,
the home agent for Mobile IPv6, and the local
mobility
anchor for Proxy Mobile IPv6), anchor) and burdening it with data forwarding and control
mechanisms for a great amount large number of users. The mobility anchor is the home agent
for Mobile IPv6 and the local mobility anchor for PMIPv6.  As stated in <xref
target="RFC7333"></xref>, target="RFC7333" format="default"/>, centralized mobility solutions are prone to several
problems and limitations: longer (sub-optimal) routing paths, scalability
problems, signaling overhead (and most likely a longer associated handover
latency), more complex network deployment, higher vulnerability due to the
existence of a potential single point of failure, and lack of granularity of the
mobility management service (i.e., mobility is offered on a per-node basis, basis
because it is not
being possible to define finer granularity policies, as for example
per-application). example,
on a per-application basis).
      </t>
      <t>
The purpose of Distributed Mobility Management DMM is to overcome the limitations of
the traditional centralized mobility management <xref target="RFC7333" /> format="default"/> <xref target="RFC7429" />; format="default"/>; the main concept behind DMM solutions is indeed bringing
the mobility anchor closer to the Mobile Node mobile node (MN). Following this idea, the
central anchor is moved to the edge of the network, being network and is deployed in the
default gateway of the mobile node. MN. That is, the first elements that provide IP
connectivity to a set of MNs are also the mobility managers for those MNs. In
this document, we call these entities Mobility Anchors and Access Routers
(MAARs).
      </t>
      <t>
This document focuses on network-based DMM, hence DMM; hence, the starting point is making
PMIPv6 work in a distributed manner <xref target="RFC7429"></xref>. target="RFC7429" format="default"/>. Mobility is
handled by the network without the MNs involvement, but, MN's involvement. But differently from
PMIPv6, when the MN moves from one access network to another, it the router
anchoring the MN's address may also change
anchor router, change, hence requiring signaling between the anchors to retrieve the
MN's previous location(s). Also, a key-aspect key aspect of network-based DMM, DMM is that a
prefix pool belongs exclusively to each MAAR, MAAR in the sense that those prefixes
are assigned by the MAAR to the MNs attached to it, it and they are routable at
that MAAR. Prefixes are assigned to MNs attached to a MAAR at that time, but remain
with those MNs as mobility occurs, remaining always routable at that MAAR as
well as towards the MN itself.
      </t>
      <t>
We consider partially distributed schemes, where only the data plane is
distributed among access routers similar to MAGs, mobile access gateways (MAGs), whereas the control plane is
kept centralized towards a cardinal node used (used as an information store, but relieved store), which
is discharged from any route management and MN's data forwarding task. tasks.
      </t>
    <section anchor="terms">
      <name>Requirements Language</name>
        <t>
    The key words "<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 "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as
    described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
    when, and only when, they appear in all capitals, as shown here.
        </t>
</section>
</section>
    <section anchor="sec:terminology" title="Terminology"> anchor="sec_terminology" numbered="true" toc="default">
      <name>Terminology</name>
      <t>
The following terms used in this document are defined in the Proxy Mobile IPv6 PMIPv6
specification <xref target="RFC5213" />:

        <list style="empty">
          <t>Local format="default"/>:

      </t>
      <ul empty="true" spacing="normal"><li>
      <dl>
        <dt>BCE:</dt><dd>Binding Cache Entry</dd>
        <dt>LMA:</dt><dd>Local Mobility Anchor (LMA)</t>

          <t>Mobile Anchor</dd>
        <dt>MAG:</dt><dd>Mobile Access Gateway (MAG)</t>

          <t>Mobile Node (MN)</t>

          <t>Binding Cache Entry (BCE)</t>

          <t>Proxy Gateway</dd>
        <dt>MN:</dt><dd>Mobile Node</dd>
        <dt>P-CoA:</dt><dd>Proxy Care-of Address (P-CoA)</t>

          <t>Proxy Address</dd>
        <dt>PBA:</dt><dd>Proxy Binding Update (PBU)</t>

          <t>Proxy Acknowledgement</dd>
        <dt>PBU:</dt><dd>Proxy Binding Acknowledgement (PBA)</t>
        </list> Update</dd>
      </dl>
      </li>
      </ul>
      <t>
The following terms used in this document are defined in the Mobile IPv6
(MIPv6) specification <xref target="RFC6275" format="default"/>:
      </t>
      <ul empty="true" spacing="normal"><li>
      <dl>
        <dt>CN:</dt><dd>Correspondent Node</dd>
      </dl></li></ul>
      <t>
The following terms are used in this document:

        <list style="hanging">
          <t hangText="Home

      </t>
      <dl newline="true" spacing="normal">
        <dt>Home Control-Plane Anchor (Home-CPA or H-CPA):"> H-CPA):</dt>
        <dd>

The Home-CPA function hosts the mobile node (MN)'s MN's mobility
session.  There can be more than one mobility session for a mobile
node an MN, and those sessions may be anchored on the same or different
Home-CPA's.
Home-CPAs.  The home-CPA Home-CPA will interface with the home-DPA Home-DPA for
managing the forwarding state.
<vspace blankLines="1"/>
          </t>

          <t hangText="Home
        </dd>
        <dt>Home Data Plane Anchor (Home-DPA or H-DPA):"> H-DPA):</dt>

        <dd>
The Home-DPA is the topological anchor for the MN's IP address/
prefix(es). addresses
and/or prefixes.
The Home-DPA is chosen by the Home-CPA on a session- session basis.  The Home-DPA is in the forwarding path for all the mobile
node's MN's IP traffic.
<vspace blankLines="1"/>
          </t>

          <t hangText="Access
        </dd>
        <dt>Access Control Plane Node (Access-CPN or A-CPN):"> A-CPN):</dt>
        <dd>

The Access-CPN is responsible for interfacing with the mobile
node's MN's Home-CPA and with the Access-DPN.  The Access-CPN has a
protocol interface to the Home-CPA.
<vspace blankLines="1"/>
          </t>

          <t hangText="Access

        </dd>
        <dt>Access Data Plane Node (Access-DPN or A-DPN):"> A-DPN):</dt>
        <dd>
The Access-DPN function is hosted on the first-hop router where
the mobile node MN is attached.  This function is not hosted on a
layer-2
Layer 2 (L2) bridging device such as a an eNode(B) or Access Point.
<vspace blankLines="1"/>
          </t>

        </list>
      </t>
        </dd>
      </dl>
      <t>
The following terms are defined and used in this document:
        <list style="hanging">

          <t hangText="MAAR
      </t>
      <dl newline="true" spacing="normal">
        <dt>MAAR (Mobility Anchor and Access Router).">
First hop Router):</dt>
        <dd>
First-hop router where the mobile nodes attach to. MNs attach. It also plays the role of
mobility manager for the IPv6 prefixes it anchors, running the functionalities
of PMIP's MAG and LMA. Depending on the prefix, it plays the role of Access-DPN,
Home-DPA
Home-DPA, and Access-CPN.
          </t>

          <t hangText="CMD
          </dd>
        <dt>CMD (Central Mobility Database)."> Database):</dt>
        <dd>
The node that stores the BCEs allocated for the MNs in the mobility domain. It plays
the role of Home-CPA.
          </t>

          <t hangText="P-MAAR
          </dd>
        <dt>P-MAAR (Previous MAAR)."> MAAR):</dt>
        <dd>
When a an MN moves to a new point of attachment attachment, a new MAAR might be allocated as
its anchor point for future IPv6 prefixes. The MAAR that served the MN prior to
new attachment becomes the P-MAAR. It is still the anchor point for the IPv6
prefixes it had allocated to the MN in the past and serves as the Home-DPA for
flows using these prefixes. There might be several P-MAARs serving a an MN in
cases when the MN is frequently switching points of attachment while
maintaining long-lasting flows.
          </t>

          <t hangText="S-MAAR
          </dd>
        <dt>S-MAAR (Serving MAAR)."> MAAR):</dt>
        <dd>
The MAAR to which the MN is currently attached to. attached. Depending on the prefix, it
plays the role of Access-DPN, Home-DPA Home-DPA, and Access-CPN.
          </t>

          <t hangText="Anchoring MAAR.">
          </dd>
        <dt>Anchoring MAAR:</dt>
        <dd>
A MAAR anchoring an IPv6 prefix used by an MN.
          </t>

          <t hangText="DLIF
          </dd>
        <dt>DLIF (Distributed Logical Interface)."> Interface):</dt>
        <dd>
It is a logical interface at the IP stack of the MAAR. For each active prefix
used by the MN, the S-MAAR has a DLIF configured (associated to with each
MAAR still anchoring flows). In this way, an S-MAAR exposes itself towards each
MN as multiple routers, one as itself and one per P-MAAR.
          </t>

        </list>
      </t>
          </dd>
      </dl>
    </section>

    <section anchor="sec:pmipv6_based" title="PMIPv6 anchor="sec_pmipv6_based" numbered="true" toc="default">
      <name>PMIPv6 DMM extensions"> Extensions</name>
      <t>
The solution consists of de-coupling decoupling the entities that participate in the data
and the control planes: the data plane becomes distributed and managed by the
MAARs near the edge of the network, while the control plane, besides those on
the MAARs, relies on a central entity called the Central Mobility Database (CMD). In
the proposed architecture, the hierarchy present in PMIPv6 between LMA and MAG
is preserved, preserved but with the following substantial variations:

        <list style="symbols">

          <t>

      </t>
      <ul spacing="normal">
        <li>
The LMA is relieved discharged from the data forwarding role, role; only the Binding Cache and
its management operations are maintained. Hence Hence, the LMA is renamed into CMD, as "CMD",
which is therefore a Home-CPA. Also, the CMD is able to send and parse both PBU
and PBA messages.
          </t>

          <t>
          </li>
        <li>
The MAG is enriched with the LMA functionalities, hence the name Mobility Anchor
and Access Router (MAAR). It maintains a local Binding Cache for the MNs that
are attached to it it, and it is able to send and parse PBU and PBA messages.
          </t>

          <t>
          </li>
        <li>
The binding cache Binding Cache will be extended to include information regarding P-MAARs
where the mobile node MN was anchored and still retains active data sessions.
          </t>

          <t>
          </li>
        <li>
Each MAAR has a unique set of global prefixes (which are configurable), configurable) that can
be allocated by the MAAR to the MNs, MNs but must be exclusive to that MAAR, i.e. i.e., no
other MAAR can allocate the same prefixes.
          </t>

        </list>

      </t>
          </li>
      </ul>
      <t>
The MAARs leverage the CMD to access and update information related to the MNs,
which is stored as mobility sessions; hence, a centralized node maintains a global view
of the network status. The CMD is queried whenever a an MN is detected to
join/leave joining/leaving the mobility domain. It might be a fresh attachment, a detachment detachment, or
a handover, but as MAARs are not aware of past information related to a mobility
session, they contact the CMD to retrieve the data of interest and eventually
take the appropriate action. The procedure adopted for the query and the
message exchange sequence might vary to optimize the update latency and/or the
signaling overhead. Here is presented Here, one method for the initial registration, registration and three different approaches for updating the mobility sessions using PBUs and
PBAs.
PBAs are presented. Each approach assigns a different role to the CMD:

        <list style="symbols">

          <t>The

      </t>
      <ul spacing="normal">
        <li>The CMD is a PBU/PBA relay;</t>

          <t>The relay;</li>
        <li>The CMD is only a MAAR locator;</t>

          <t>The locator;</li>
        <li>The CMD is a PBU/PBA proxy.</t>

        </list>

      </t> proxy.</li>
      </ul>
      <t>
The solution described in this document allows performing per-prefix anchoring
decisions,
decisions -- for example, to support e.g., the anchoring of some flows to be anchored at a central Home-DPA
(like a traditional LMA) or to enable an application to switch to the locally
anchored prefix to gain route optimization, as indicated in <xref target="RFC8563" />. format="default"/>. This type of per-prefix treatment would potentially require
additional extensions to the MAARs and signaling between the MAARs and the MNs
to convey the per-flow anchor preference (central, distributed), which are not
covered in this document.
      </t>
      <t>
Note that a an MN may move across different MAARs, which might result in several
P-MAARs existing at a given moment of time, each of them anchoring a different
prefix used by the MN.
      </t>
      <section anchor="subsec:init" title="Initial registration"> anchor="subsec_init" numbered="true" toc="default">
        <name>Initial Registration</name>
        <t>
Initial registration is performed when an MN attaches to a network for the first
time (rather than attaching to a new network after moving from a previous one).
        </t>
        <t>
In this description (shown in <xref target="fig:DMM1" />), target="fig_DMM1" format="default"/>), it is assumed that:

          <list style="numbers">

            <t>

        </t>
        <ol spacing="normal" type="1">
          <li>
The MN is attaching to MAAR1.
            </t>

            <t>
            </li>
          <li>
The MN is authorized to attach to the network.
            </t>

          </list>

        </t>
            </li>
        </ol>
        <t>
Upon MN attachment, the following operations take place:

          <list style="numbers">

            <t>

        </t>
        <ol spacing="normal" type="1">
          <li>
MAAR1 assigns a global IPv6 prefix from its own prefix pool to the MN (Pref1).
It also stores this prefix (Pref1) in the locally allocated temporary Binding
Cache Entry (BCE).
            </t>

            <t> BCE.
            </li>
          <li>
MAAR1 sends a PBU <xref target="RFC5213" /> format="default"/> with Pref1 and the MN's MN-ID to the
CMD.
            </t>

            <t>
            </li>
          <li>
Since this is an initial registration, the CMD stores a BCE containing as
primary fields the
MN-ID, Pref1 Pref1, and MAAR1's address as (as a Proxy-CoA.
            </t>

            <t> Proxy-CoA) as the primary fields.
            </li>
          <li>
The CMD replies with a PBA with the usual options defined in PMIPv6 <xref target="RFC5213" />, format="default"/>, meaning that the MN's registration is fresh and no past
status is available.
            </t>

            <t>
            </li>
          <li>
MAAR1 stores the BCE described in (1) and unicasts a Router Advertisement (RA) to
the MN with Pref1.
            </t>

            <t>
            </li>
          <li>
The MN uses Pref1 to configure an IPv6 address (IP1) (e.g., with stateless
auto-configuration, SLAAC).
            </t>

          </list>

        </t>
address autoconfiguration (SLAAC)).
            </li>
        </ol>
        <t>
Note that:
          <list style="numbers">

            <t>
        </t>
        <ol spacing="normal" type="1">
          <li>
Alternative IPv6 auto-configuration autoconfiguration mechanisms can also be used, though this
document describes the SLAAC-based one.
            </t>

            <t>
            </li>
          <li>
IP1 is routable at MAAR1, MAAR1 in the sense that it is on the path of packets
addressed to the MN.
            </t>

            <t>
            </li>
          <li>
MAAR1 acts as a plain router for packets destined to the MN, MN as no encapsulation
nor
or special handling takes place.
        </t>

          </list>

        </t>
        </li>
        </ol>
        <t>
In the diagram shown in <xref target="fig:DMM1" /> target="fig_DMM1" format="default"/> (and subsequent diagrams),
the flow of packets is presented using '*'.
        </t>

        <figure anchor="fig:DMM1" title="First attachment anchor="fig_DMM1">
          <name>First Attachment to the network">
          <artwork><![CDATA[ Network</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
  +-----+      +---+                +--+
  |MAAR1|      |CMD|                |CN|
  +-----+      +---+                +*-+
     |           |                   *
    MN           |                   *     +---+
  attach.        |               *****    _|CMD|_
detection        |         flow1 *       / +-+-+ \
     |           |               *      /    |    \
 local BCE       |               *     /     |     \
 allocation      |               *    /      |      \
     |--- PBU -->|           +---*-+-'    +--+--+    `+-----+
     |          BCE          |   * |      |     |     |     |
     |        creation       |MAAR1+------+MAAR2+-----+MAAR3|
     |<-- PBA ---|           |   * |      |     |     |     |
 local BCE       |           +---*-+      +-----+     +-----+
 finalized       |               *
     |           |         Pref1 *
     |           |              +*-+
     |           |              |MN|
     |           |              +--+

  Operations sequence                  Packets                  Packet flow
]]></artwork>
        </figure>
        <t>
Note that the registration process does not change regardless of the CMD's modes
(relay, locator locator, or proxy) described next. in the following sections. The procedure is depicted in <xref
target="fig:DMM1" />. target="fig_DMM1" format="default"/>.
        </t>
      </section>
      <section anchor="subsec:relay" title="The anchor="subsec_relay" numbered="true" toc="default">
        <name>The CMD as PBU/PBA relay"> Relay</name>
        <t>
Upon MN mobility, if the CMD behaves as a PBU/PBA relay, the following operations take place:

          <list style="numbers">

            <t>

        </t>
        <ol spacing="normal" type="1">
          <li>
When the MN moves from its current point of attachment and attaches to MAAR2
(now the S-MAAR), MAAR2 reserves an IPv6 prefix (Pref2), it stores a temporary
BCE, and it sends a PBU to the CMD for registration.
            </t>

            <t>
            </li>
          <li>
Upon PBU reception and BC lookup, the CMD retrieves an already existing entry
for the MN, binding MN and binds the MN-ID to its former location; thus, the CMD forwards the
PBU to the MAAR indicated as Proxy CoA (MAAR1), including Proxy-CoA (MAAR1) and includes a new mobility option
to communicate the S-MAAR's global address to MAAR1, defined MAAR1 (defined as the Serving MAAR
Option
option in <xref target="subsec:smaaropt" />. target="subsec_smaaropt" format="default"/>). The CMD updates the P-CoA field in
the BCE related to the MN with the S-MAAR's address.
            </t>

            <t>
            </li>
          <li>
Upon PBU reception, MAAR1 can install a tunnel on its side towards MAAR2 and the
related routes for Pref1. Then MAAR1 replies to the CMD with a PBA (including
the option mentioned before) to ensure that the new location has successfully
changed, containing
changed. The PBA contains the prefix anchored at MAAR1 in the Home Network Prefix
option.
            </t>

            <t>
            </li>
          <li>
The CMD, after receiving the PBA, updates the BCE populating and populates an instance
of the P-MAAR list. The P-MAAR list is an additional field on the BCE that
contains an element for each P-MAAR involved in the MN's mobility session. The
list element contains the P-MAAR's global address and the prefix it has
delegated. Also, the
CMD sends a PBA to the new S-MAAR, containing which contains the previous Proxy-CoA and the
prefix anchored to it embedded into a new mobility option called the Previous MAAR
Option
option (defined in <xref target="subsec:pmaaropt"></xref>), so that, target="subsec_pmaaropt" format="default"/>). Then, upon PBA
arrival, a bi-directional bidirectional tunnel can be established between the two MAARs MAARs, and
new routes are set appropriately to recover the IP flow(s) carrying Pref1.
            </t>

            <t>
Now
            </li>
          <li>
Now, packets destined to for Pref1 are first received by MAAR1, encapsulated into the
tunnel
tunnel, and forwarded to MAAR2, which finally delivers them to their destination.
In the uplink, when the MN transmits packets using Pref1 as a source address, they are
sent to MAAR2, as MAAR2 (as it is the MN's new default gateway, gateway) and then tunneled to MAAR1 MAAR1, which
routes them towards the next hop to the destination. Conversely, packets carrying
Pref2 are routed by MAAR2 without any special packet handling both for the uplink
and downlink.
            </t>

          </list>

        </t>
            </li>
        </ol>
        <figure anchor="fig:DMM2"
                title="Scenario anchor="fig_DMM2">
          <name>Scenario after a handover, Handover, CMD as relay">
          <artwork><![CDATA[ Relay</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
+-----+      +---+      +-----+           +--+            +--+
|MAAR1|      |CMD|      |MAAR2|           |CN|            |CN|
+-----+      +---+      +-----+           +*-+            +*-+
   |           |           |               *               *
   |           |          MN               *     +---+     *
   |           |        attach.        *****    _|CMD|_    *
   |           |          det.   flow1 *       / +-+-+ \   *flow2
   |           |<-- PBU ---|           *      /    |    \  *
   |          BCE          |           *     /     | *******
   |        check+         |           *    /      | *    \
   |        update         |       +---*-+-'    +--+-*+    `+-----+
   |<-- PBU*---|           |       |   * |      |    *|     |     |
route          |           |       |MAAR1|______|MAAR2+-----+MAAR3|
update         |           |       |   **(______)**  *|     |     |
   |--- PBA*-->|           |       +-----+      +-*--*+     +-----+
   |         BCE           |                      *  *
   |        update         |                Pref1 *  *Pref2
   |           |--- PBA*-->|                     +*--*+
   |           |         route         ---move-->|*MN*|
   |           |         update                  +----+

      Operations sequence                  Data Packets Packet flow
PBU/PBA Messages messages with * contain
     a new mobility option
]]></artwork>
        </figure>
        <t>
For MN's next movements movements, the process is repeated except repeated, but the number of P-MAARs
involved increases (accordingly (according to the number of prefixes that the MN wishes to
maintain). Indeed, once the CMD receives the first PBU from the new S-MAAR, it
forwards copies of the PBU to all the P-MAARs indicated in the BCE, namely the
one
P-MAAR registered as the current P-CoA (i.e., the MAAR prior to handover) plus the ones
in the P-MAARs P-MAAR list. They Those P-MAARs reply with a PBA to the CMD, which
aggregates them all of the PBAs into a single one PBA to notify the S-MAAR, that which finally can establish the tunnels
with the P-MAARs.
        </t>

        <t>
It should be noted that this design separates the mobility management at the
prefix granularity, and it can be tuned in order to erase old mobility sessions
when not required, while the MN is reachable through the latest prefix acquired.
Moreover, the latency associated to with the mobility update is bound to the PBA sent
by the furthest P-MAAR, in terms of RTT, that takes the longest time to reach
the CMD. The drawback can be mitigated by introducing a timeout at the CMD, by
which, after its expiration, all the PBAs so far collected are transmitted, and
the remaining are sent later upon their arrival. Note that that, in this case case, the
S-MAAR might receive multiple PBAs from the CMD in response to a PBU. The CMD
SHOULD
<bcp14>SHOULD</bcp14> follow the retransmissions and rate limiting rate-limiting considerations described in
<xref target="sec:retransmissions" />, target="sec_retransmissions" format="default"/>, especially when aggregating and relaying
PBAs.
        </t>
        <t>
When there are multiple previous MAARs, P-MAARs, e.g., k MAARs, a single PBU received by
the CMD triggers k outgoing packets from a single incoming packet. This may lead
to packet bursts originated originating from the CMD, albeit to different targets. Pacing
mechanisms MUST <bcp14>MUST</bcp14> be introduced to avoid bursts on the outgoing link.
        </t>
      </section>
      <section anchor="subsec:locator" title="The anchor="subsec_locator" numbered="true" toc="default">
        <name>The CMD as MAAR locator"> Locator</name>

        <t>
The handover latency experienced in the approach shown before can be reduced if
the P-MAARs are allowed to signal directly signal their information to the new S-MAAR.
This procedure reflects what was described in <xref target="subsec:relay" /> target="subsec_relay" format="default"/> up
to the moment the P-MAAR receives the PBU with the S-MAAR Serving MAAR option. At that point point,
a P-MAAR is aware of the new MN's location (because of the S-MAAR's address in
the S-MAAR Serving MAAR option), and, besides sending a PBA to the CMD, it also sends a PBA
to the S-MAAR S-MAAR, including the prefix it is anchoring. This latter PBA does not
need to include new options, as the prefix is embedded in the HNP Home
Network Prefix (HNP) option and the
P-MAAR's address is taken from the message's source address. The CMD is relieved
released from forwarding the PBA to the S-MAAR, S-MAAR as the latter receives a copy directly
from the P-MAAR with the necessary information to build the tunnels and set the
appropriate routes. <xref target="fig:DMM3" /> target="fig_DMM3" format="default"/> illustrates the new message
sequence, while the
sequence. The data forwarding is unaltered.
        </t>
        <figure anchor="fig:DMM3"
                title="Scenario anchor="fig_DMM3">
          <name>Scenario after a handover, Handover, CMD as locator">
          <artwork><![CDATA[ Locator</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
+-----+      +---+      +-----+           +--+            +--+
|MAAR1|      |CMD|      |MAAR2|           |CN|            |CN|
+-----+      +---+      +-----+           +*-+            +*-+
   |           |           |               *               *
   |           |          MN               *     +---+     *
   |           |        attach.        *****    _|CMD|_    *
   |           |          det.   flow1 *       / +-+-+ \   *flow2
   |           |<-- PBU ---|           *      /    |    \  *
   |          BCE          |           *     /     | *******
   |        check+         |           *    /      | *    \
   |        update         |       +---*-+-'    +--+-*+    `+-----+
   |<-- PBU*---|           |       |   * |      |    *|     |     |
route          |           |       |MAAR1|______|MAAR2+-----+MAAR3|
update         |           |       |   **(______)**  *|     |     |
   |--------- PBA -------->|       +-----+      +-*--*+     +-----+
   |--- PBA*-->|         route                    *  *
   |          BCE        update             Pref1 *  *Pref2
   |         update        |                     +*--*+
   |           |           |           ---move-->|*MN*|
   |           |           |                     +----+

       Operations sequence                  Data Packets Packet flow
PBU/PBA Messages messages with * contain
     a new mobility option
]]></artwork>
        </figure>
      </section>
      <section anchor="subsec:proxy" title="The anchor="subsec_proxy" numbered="true" toc="default">
        <name>The CMD as MAAR proxy"> PBU/PBA Proxy</name>
        <t>
A further enhancement of previous solutions can be achieved when the CMD sends
the PBA to the new S-MAAR before notifying the P-MAARs of the location change.
Indeed, when the CMD receives the PBU for the new registration, it is already in
possession of all the information that the new S-MAAR requires to set up the
tunnels and the routes. Thus Thus, the PBA is sent to the S-MAAR immediately after a
PBU is received, including also the Previous MAAR option in this case the P-MAAR option. case. In parallel, a
PBU is sent by the CMD to the P-MAARs containing the S-MAAR option, Serving MAAR option to notify
them about the new MN's location, location so that they receive the information to establish
the tunnels and routes on their side. When P-MAARs complete the update, they
send a PBA to the CMD to indicate that the operation is has concluded and the
information is updated in all network nodes. This procedure is obtained from
the first one re-arranging procedure rearranging the order of the messages, but the parameters
communicated are the same. This scheme is depicted in <xref
target="fig:DMM4"></xref>, target="fig_DMM4" format="default"/>, where, again, the data forwarding is kept untouched.
        </t>
        <figure anchor="fig:DMM4"
                title="Scenario anchor="fig_DMM4">
          <name>Scenario after a handover, Handover, CMD as proxy">
          <artwork><![CDATA[ Proxy</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
+-----+      +---+      +-----+           +--+            +--+
|MAAR1|      |CMD|      |MAAR2|           |CN|            |CN|
+-----+      +---+      +-----+           +*-+            +*-+
   |           |           |               *               *
   |           |          MN               *     +---+     *
   |           |        attach.        *****    _|CMD|_    *
   |           |          det.   flow1 *       / +-+-+ \   *flow2
   |           |<-- PBU ---|           *      /    |    \  *
   |          BCE          |           *     /     | *******
   |        check+         |           *    /      | *    \
   |        update         |       +---*-+-'    +--+-*+    `+-----+
   |<-- PBU*---x--- PBA*-->|       |   * |      |    *|     |     |
route          |         route     |MAAR1|______|MAAR2+-----+MAAR3|
update         |         update    |   **(______)**  *|     |     |
   |--- PBA*-->|           |       +-----+      +-*--*+     +-----+
   |          BCE          |                      *  *
   |         update        |                Pref1 *  *Pref2
   |           |           |                     +*--*+
   |           |           |           ---move-->|*MN*|
   |           |           |                     +----+

       Operations sequence                 Data Packets Packet flow
PBU/PBA Messages messages with * contain
     a new mobility option
]]></artwork>
        </figure>
      </section>
      <section anchor="subsec:dereg" title="De-registration"> anchor="subsec_dereg" numbered="true" toc="default">
        <name>De-registration</name>

        <t>
The de-registration mechanism devised for PMIPv6 cannot be used as-is as is in this
solution. The reason for this is that
solution because each MAAR handles an independent mobility
session (i.e., a single prefix or a set of prefixes) for a given MN, whereas the
aggregated session is stored at the CMD. Indeed, if a previous MAAR P-MAAR initiates
a de-registration procedure, procedure because the MN is no longer present on the MAAR's
access link, it removes the routing state for that (those) the prefix(es), that
would be deleted by the CMD as well, hence defeating any prefix continuity
attempt. The simplest approach to overcome this limitation is to deny a P-MAAR
to de-register a prefix, that is, allowing only a serving MAAR an S-MAAR to de-register
the whole MN session. This can be achieved by first removing any layer-2 L2
detachment event, event so that de-registration is triggered only when the binding
lifetime expires, hence providing a guard interval for the MN to connect to a
new MAAR. Then, a change in the MAAR operations is required, and at this stage stage,
two possible solutions can be deployed:

          <list style="symbols">

            <t>

        </t>
        <ul spacing="normal">
          <li>
A previous MAAR P-MAAR stops the BCE timer upon receiving a PBU from the CMD containing
a "Serving MAAR" option. In this way way, only the Serving MAAR S-MAAR is allowed to
de-register the mobility session, arguing that the MN definitely left the
domain.
            </t>

            <t>
Previous MAARs
            </li>
          <li>
P-MAARs can, upon BCE expiry, send de-registration messages to the CMD,
which, instead of acknowledging the message with a 0 lifetime, sends back a PBA
with a non-zero lifetime, hence re-newing renewing the session, session if the MN is still
connected to the domain.
            </t>

          </list>

        </t>
            </li>
        </ul>
      </section>
      <section anchor="sec:retransmissions" title="Retransmissions anchor="sec_retransmissions" numbered="true" toc="default">
        <name>Retransmissions and Rate Limiting"> Limiting</name>
        <t>
When sending PBUs, the
The node sending them PBUs (the CMD or S-MAAR) SHOULD <bcp14>SHOULD</bcp14> make use of
the timeout also to also deal with missing PBAs (to retransmit PBUs). The
INITIAL_BINDACK_TIMEOUT <xref target="RFC6275" /> SHOULD format="default"/> <bcp14>SHOULD</bcp14> be used for configuring
the retransmission timer. The retransmissions by the node MUST <bcp14>MUST</bcp14> use an
exponential backoff process in which the timeout period is doubled upon each
retransmission,
retransmission until either the node receives a response or the timeout period
reaches the value MAX_BINDACK_TIMEOUT <xref target="RFC6275" />. format="default"/>. The node MAY <bcp14>MAY</bcp14>
continue to send these messages at this slower rate indefinitely. The node MUST
NOT <bcp14>MUST
NOT</bcp14> send PBU messages to a particular node more than MAX_UPDATE_RATE times
within a second <xref target="RFC6275" />. format="default"/>.
        </t>
      </section>
      <section anchor="sec:dlif_concept" title="The anchor="sec_dlif_concept" numbered="true" toc="default">
        <name>The Distributed Logical Interface (DLIF) concept"> Concept</name>
        <t>
One of the main challenges of a network-based DMM solution is how to allow a
mobile node
MN to simultaneously send/receive traffic which that is anchored at
different MAARs, MAARs and how to influence the mobile node's MN's selection process of its
source IPv6 address for a new flow, flow without requiring special support from the
mobile node's
MN's IP stack. This document defines the Distributed Logical Interface
(DLIF), DLIF, which is a software construct in the MAAR that allows to can easily hide
the change of associated anchors from the mobile node. MN.
        </t>
        <figure anchor="fig:exposing_multiple_routers"
              title="DLIF: exposing multiple routers (one anchor="fig_exposing_multiple_routers">
          <name>DLIF: Exposing Multiple Routers (One per P-MAAR)">
        <artwork><![CDATA[ P-MAAR)</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
  +---------------------------------------------------+
 (                      Operator's                     )
 (                         core                        )
  +---------------------------------------------------+
            |                               |
    +---------------+     tunnel    +---------------+
    |   IP  stack   |===============|   IP  stack   |
    +---------------+               +-------+-------+
    |    mn1mar1    |--+ (DLIFs) +--|mn1mar1|mn1mar2|--+
    +---------------+  |         |  +-------+-------+  |
    | phy interface |  |         |  | phy interface |  |
    +---------------+  |         |  +---------------+  |
          MAAR1       (o)       (o)       MAAR2       (o)
                                   x                 x
                                     x             x
                        prefA::/64     x         x   prefB::/64
                      (AdvPrefLft=0)     x     x
                                           (o)
                                            |
                                         +-----+
                             prefA::MN1  | MN1 |  prefB::MN1
                            (deprecated) +-----+
]]></artwork>
        </figure>
        <t>
The basic idea of the DLIF concept is the following: each serving MAAR S-MAAR exposes
itself towards to a given MN as multiple routers, one per P-MAAR
associated to with the MN. Let's consider the example shown in <xref
target="fig:exposing_multiple_routers" />, target="fig_exposing_multiple_routers" format="default"/>: MN1 initially attaches to MAAR1,
configuring an IPv6 address (prefA::MN1) from a prefix locally anchored at MAAR1
(prefA::/64). At this stage, MAAR1 plays both the role of both anchoring and serving
MAAR,
MAAR and also behaves as a plain IPv6 access router. MAAR1 creates a distributed
logical interface DLIF to communicate (point-to-point (through a point-to-point link) with MN1, exposing itself
as a (logical) router with a specific MAC and IPv6
addresses (e.g., prefA::MAAR1/64 and fe80::MAAR1/64) using the DLIF
mn1mar1. As explained below, these addresses represent the "logical" identity of
MAAR1 towards MN1, for MN1 and will "follow" the mobile node MN while roaming within the
domain (note that the place where all this information is maintained and updated
is out-of-scope out of scope of this draft; document; potential examples are to keep it on the home
subscriber server -- HSS -- or the user's profile).
        </t>
        <t>
If MN1 moves and attaches to a different MAAR of the domain (MAAR2 in the
example of <xref target="fig:exposing_multiple_routers" />), target="fig_exposing_multiple_routers" format="default"/>), this MAAR will
create a new logical interface (mn1mar2) to expose itself towards to MN1, providing
it with a locally anchored prefix (prefB::/64). In this case, since the MN1 has
another active IPv6 address anchored at a MAAR1, MAAR2 also needs to create an
additional logical interface configured to resemble the one used by MAAR1 to
communicate with MN1. In this example, there MAAR1 is the only one P-MAAR (in addition to
MAAR2, which (MAAR2 is the serving one): MAAR1, the
same as S-MAAR), so only the logical interface mn1mar1
is created, but created. However, the same process would be repeated in case there were if more
P-MAARs were involved. In order to maintain keep the prefix anchored at MAAR1 reachable, a
tunnel between MAAR1 and MAAR2 is established and the routing is modified
accordingly. The PBU/PBA signaling is used to set-up set up the bi-directional bidirectional tunnel
between MAAR1 and MAAR2, and it might also be used to convey to MAAR2 the
information about the prefix(es) anchored at MAAR1 and about the addresses of
the associated DLIF (i.e., mn1mar1). mn1mar1) to MAAR2.
        </t>
        <figure anchor="fig:dlif_concept"
              title="Distributed anchor="fig_dlif_concept">
          <name>Distributed Logical Interface concept">
        <artwork><![CDATA[ Concept</name>
          <artwork name="" type="" align="left" alt=""><![CDATA[
+------------------------------------------+ +----------------------+
|                  MAAR1                   | |         MAAR2        |
|+----------------------------------------+| |+--------------------+|
||+------------------++------------------+|| ||+------------------+||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
||||mn3mar1||mn3mar2||||mn2mar1||mn2mar2|||| ||||mn1mar1||mn1mar2||||
|||| LMAC1 || LMAC2 |||| LMAC3 || LMAC4 |||| |||| LMAC5 || LMAC6 ||||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
|||    LIFs of MN3   ||    LIFs of MN2   ||| |||   LIFs of MN1    |||
||+------------------++------------------+|| ||+------------------+||
||              MAC1   (phy if MAAR1)     || || MAC2 (phy if MAAR2)||
|+----------------------------------------+| |+--------------------+|
+------------------------------------------+ +----------------------+
                    x        x                            x
                   x          x                          x
                 (o)          (o)                      (o)
                  |            |                        |
               +--+--+      +--+--+                  +--+--+
               | MN3 |      | MN2 |                  | MN1 |
               +-----+      +-----+                  +-----+
]]></artwork>
        </figure>
        <t>
<xref target="fig:dlif_concept" /> target="fig_dlif_concept" format="default"/> shows the logical interface concept in more
detail. The figure shows two MAARs and three MNs. MAAR1 is currently serving MN2
and MN3, while MAAR2 is serving MN1. Note that a serving MAAR an S-MAAR always plays the
role of anchoring MAAR for the attached (served) MNs. Each MAAR has one single
physical wireless interface as depicted in this example.
        </t>
        <t>
As introduced discussed before, each MN always "sees" multiple logical routers -- one per
anchoring MAAR -- independently of its currently serving MAAR. S-MAAR. From the point of
view of the MN, these MAARs are portrayed as different routers, although the MN
is physically attached to one a single interface. The way this This is achieved is by
the serving MAAR S-MAAR configuring different logical interfaces. Focusing on MN1, it MN1 is currently attached to MAAR2 (i.e., MAAR2 is its serving MAAR) S-MAAR) and, therefore,
it has configured an IPv6 address from MAAR2's pool (e.g., prefB::/64). MAAR2
has set-up set up a logical interface (mn1mar2) on top of its wireless physical
interface (phy if MAAR2) MAAR2), which is used to serve MN1. This interface has a
logical MAC address (LMAC6), (LMAC6) that is different from the hardware MAC address (MAC2) of
the physical interface of MAAR2. Over the mn1mar2 interface, MAAR2 advertises
its locally anchored prefix prefB::/64.

Before attaching to MAAR2, MN1 was
attached to MAAR1, configuring also an address MAAR1 and configured a locally anchored address at that MAAR,
which is still being used by MN1 in active communications. MN1 keeps "seeing" an
interface connecting to MAAR1, MAAR1 as if it were directly connected to the two
MAARs. This is achieved by the serving MAAR S-MAAR (MAAR2) configuring an additional
distributed logical interface:
DLIF, mn1mar1, which behaves as the logical interface
configured by MAAR1 when MN1 was attached to it. This means that both the MAC
and IPv6 addresses configured on this logical interface remain the same
regardless of the physical MAAR which that is serving the MN. The information
required by a serving MAAR an S-MAAR to properly configure this logical interfaces can be
obtained in different ways: as part of the information conveyed in the PBA, from
an external database (e.g., the HSS) or by other means. As shown in the figure,
each MAAR may have several logical interfaces associated to with each attached MN,
having MN
and always has at least one (since a serving MAAR an S-MAAR is also an anchoring MAAR for
the attached MN).
        </t>
        <t>
In order to enforce the use of the prefix locally anchored at the serving MAAR, S-MAAR,
the router advertisements RAs sent over those logical interfaces playing the role of
anchoring MAARs (different from the serving one) include a zero preferred prefix
lifetime (and a non-zero valid prefix lifetime, so the prefix remains valid, valid
while being deprecated). The goal is to deprecate the prefixes delegated by
these MAARs (so that they will no longer be serving the MN). Note that on-going ongoing
communications may keep on using those addresses, addresses even if they are deprecated,
so this only affects the establishment of new sessions.
        </t>
        <t>
The distributed logical interface DLIF concept also enables the following use case:
suppose that access to a local IP network is provided by a given MAAR (e.g.,
MAAR1 in the example shown in <xref target="fig:exposing_multiple_routers" />) target="fig_exposing_multiple_routers" format="default"/>)
and that the resources available at that network cannot be reached from outside
the local network (e.g., cannot be accessed by an MN attached to MAAR2). This is
similar to the local IP access scenario considered by 3GPP, where a local
gateway node is selected for sessions requiring access to services provided
locally (instead of going through a central gateway). The goal is to allow an MN
to be able to roam while still being able to have connectivity to this local IP
network. The solution adopted to support this case makes use of more specific
routes, as discussed in RFC 4191 <xref target="RFC4191" /> more specific routes format="default"/>, when the MN moves to a MAAR different
from the one providing access to the local IP network (MAAR1 in the
example).

These routes are advertised through the distributed logical interface
representing DLIF where
the MAAR is providing access to the local network (MAAR1 in this
example). In this way, if MN1 moves from MAAR1 to MAAR2, any active session that
MN1 may have with a node on the local network connected to MAAR1 will survive
via the tunnel between MAAR1 and MAAR2. Also, any potential future connection
attempt towards to the local network will be supported, supported even though MN1 is no
longer attached to MAAR1. MAAR1, so long as a source address configured from MAAR1 is
selected for new connections (see <xref target="RFC6724"/>, rule 5.5).
        </t>
      </section>
    </section>
    <!-- end of section "PMIPv6-based" -->
    <section anchor="subsec:messages" title="Message Format"> anchor="subsec_messages" numbered="true" toc="default">
      <name>Message Format</name>
      <t>
This section defines extensions to the Proxy Mobile IPv6 PMIPv6 <xref target="RFC5213"
/> format="default"/> protocol messages.
      </t>
      <section anchor="sec:pbu_format" title="Proxy anchor="sec_pbu_format" numbered="true" toc="default">
        <name>Proxy Binding Update"> Update</name>
        <t>
A new flag (D) is included in the Proxy Binding Update PBU to indicate that the
Proxy Binding Update
PBU is coming from a MAAR or a CMD and not from a mobile access
gateway. MAG. The rest of the Proxy Binding Update PBU format remains the same as defined
in <xref target="RFC5213" />. format="default"/>.
        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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
                                +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                |            Sequence #         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R|P|F|T|B|S|D| Rsrvd |            Lifetime           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
.                                                               .
.                        Mobility options Options                       .
.                                                               .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
<dl newline="true" spacing="normal">
        <dt>
DMM Flag (D)

            <list>

              <t> (D)</dt>
<dd>
The D Flag flag is set to indicate to the receiver of the message that the Proxy
Binding Update PBU is from a MAAR or a CMD. When an LMA that does not support the
extensions described in this document receives a message with the D-Flag D flag set,
the PBU in that case MUST NOT <bcp14>MUST NOT</bcp14> be processed by the LMA LMA, and an error MUST <bcp14>MUST</bcp14> be
returned.
              </t>

            </list>

          </t>

          <t>
Mobility Options

            <list>

              <t>
              </dd>
<dt>Mobility Options</dt>
<dd>
Variable-length field of such length that the complete Mobility Header is an
integer that is a multiple of 8 octets long. This field contains zero or more TLV-encoded
mobility options. The encoding and format of the defined options are described in
Section 6.2 of <xref target="RFC6275" />. sectionFormat="of" section="6.2"/>. The receiving node MUST <bcp14>MUST</bcp14> ignore and
skip any options that it does not understand.
              </t>

            </list>

          </t>
              </dd>
</dl>
      </section>
      <section anchor="sec:pba_format" title="Proxy anchor="sec_pba_format" numbered="true" toc="default">
        <name>Proxy Binding Acknowledgment"> Acknowledgement</name>
        <t>
A new flag (D) is included in the Proxy Binding Acknowledgment PBA to indicate that
the sender supports operating as a MAAR or CMD. The rest of the Proxy Binding
Acknowledgment PBA format remains the same as defined in <xref target="RFC5213" />. format="default"/>.
        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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
                                +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                |   Status      |K|R|P|T|B|S|D| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Sequence #            |           Lifetime            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
.                                                               .
.                        Mobility options Options                       .
.                                                               .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
        <dl newline="true" spacing="normal">
<dt>
DMM Flag (D)

            <list>

              <t> (D)</dt>
<dd>
The D flag is set to indicate that the sender of the message supports operating
as a MAAR or a CMD. When a MAG that does not support the extensions described in
this document receives a message with the D-Flag D flag set, it MUST <bcp14>MUST</bcp14> ignore the message message,
and an error MUST <bcp14>MUST</bcp14> be returned.
              </t>

            </list>

          </t>

          <t>
Mobility Options

            <list>

              <t>
</dd>
<dt>Mobility Options</dt>
<dd>
Variable-length field of such length that the complete Mobility Header is an
integer multiple of 8 octets long. This field contains zero or more TLV-encoded
mobility options. The encoding and format of the defined options are described in
Section 6.2 of <xref target="RFC6275" />. sectionFormat="of" section="6.2"/>. The MAAR MUST <bcp14>MUST</bcp14> ignore and skip any
options that it does not understand.
              </t>

            </list>

          </t>
              </dd>
        </dl>
      </section>
      <section anchor="sec:anchored_prefix_format"
                 title="Anchored anchor="sec_anchored_prefix_format" numbered="true" toc="default">
        <name>Anchored Prefix Option"> Option</name>
        <t>
A new Anchored Prefix option is defined for use with the Proxy Binding Update PBU and Proxy Binding Acknowledgment PBA messages exchanged between MAARs and CMDs.
Therefore, this option can only appear if the D bit is set in a PBU/PBA. This
option is used for exchanging the mobile node's MN's prefix anchored at the anchoring
MAAR. There can be multiple Anchored Prefix options present in the message.
        </t>
        <t>
The Anchored Prefix Option option has an alignment requirement of 8n+4. Its format is
as follows:

        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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     |   Length      |   Reserved    | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                        Anchored Prefix                        +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
Type

            <list>

              <t>
IANA-1.
              </t>

            </list>

          </t>

          <t>
Length

            <list>

              <t>
<dl newline="true" spacing="normal"><dt>
Type</dt>
<dd>65</dd>

<dt>Length</dt>
<dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields. This field MUST <bcp14>MUST</bcp14> be set to 18.
              </t>

            </list>

          </t>

          <t>
Reserved

            <list>

              <t>
              </dd>
<dt>
Reserved</dt>
<dd>
This field is unused for now. at the time of publication. The value MUST <bcp14>MUST</bcp14> be initialized to 0 by the sender
and MUST <bcp14>MUST</bcp14> be ignored by the receiver.
              </t>

            </list>

          </t>

          <t>
</dd>
<dt>
Prefix Length

            <list>

              <t>
        </dt>
<dd>
8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix
contained in the option.
              </t>

            </list>

          </t>

          <t>
              </dd>
<dt>
Anchored Prefix

            <list>

              <t>
        </dt>
<dd>
A sixteen-octet 16-octet field containing the mobile node's MN's IPv6 Anchored Prefix. Only the
first Prefix Length bits are valid for the Anchored Prefix. Prefix option. The rest of the
bits MUST <bcp14>MUST</bcp14> be ignored.
              </t>

            </list>

          </t>
              </dd>
        </dl>
      </section>
      <section anchor="sec:local_prefix_format" title="Local anchor="sec_local_prefix_format" numbered="true" toc="default">
        <name>Local Prefix Option"> Option</name>
        <t>
A new Local Prefix option is defined for use with the Proxy Binding Update PBU and
Proxy Binding Acknowledgment PBA messages exchanged between MAARs or between a MAAR
and a CMD. Therefore, this option can only appear if the D bit is set in a
PBU/PBA. This option is used for exchanging a prefix of a local network that is
only reachable via the anchoring MAAR. There can be multiple Local Prefix
options present in the message.
        </t>
        <t>
The Local Prefix Option option has an alignment requirement of 8n+4. Its format is
as follows:
        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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     |   Length      |   Reserved    | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                         Local Prefix                          +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
]]></artwork>
<dl newline="true" spacing="normal">
<dt>
Type

            <list>

              <t>
IANA-2.
              </t>

            </list>

          </t>

          <t>
</dt>
<dd>
66
              </dd>
<dt>
Length

            <list>

              <t>
        </dt>
<dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields. This field MUST <bcp14>MUST</bcp14> be set to 18.
              </t>

            </list>

          </t>

          <t>
              </dd>
<dt>
Reserved

            <list>

              <t>
        </dt>
<dd>
This field is unused for now. at the time of publication. The value MUST <bcp14>MUST</bcp14> be initialized to 0 by the sender
and MUST <bcp14>MUST</bcp14> be ignored by the receiver.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
Prefix Length

            <list>

              <t>
        </dt>
<dd>
8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix
contained in the option.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
Local Prefix

            <list>

              <t>
        </dt>
          <dd>
A sixteen-octet 16-octet field containing the IPv6 Local Prefix. Only the first Prefix
Length bits are valid for the IPv6 Local Prefix. The rest of the bits MUST <bcp14>MUST</bcp14> be
ignored.
              </t>

            </list>

          </t>
</dd>
        </dl>
      </section>
      <section anchor="subsec:pmaaropt" title="Previous anchor="subsec_pmaaropt" numbered="true" toc="default">
        <name>Previous MAAR Option"> Option</name>
        <t>
This new option is defined for use with the Proxy Binding Acknowledgement PBA messages exchanged by the CMD to a MAAR. This option is used to notify the
S-MAAR about the previous MAAR's P-MAAR's global address and the prefix anchored to it.
There can be multiple Previous MAAR options present in the message. Its format
is as follows:
        </t>
        <t>
The Previous MAAR Option option has an alignment requirement of 8n+4. Its format is
as follows:

        </t>

          <figure>
            <artwork><![CDATA[
        <artwork name="" type="" align="left" 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     |     Length    |   Reserved    | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                     P-MAAR's address                     Previous MAAR                             +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                    Home Network Prefix                        +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
          </figure>

          <t>Type

            <list>
              <t>
IANA-3.
              </t>
            </list>
          </t>

          <t>
<dl newline="true" spacing="normal">
<dt>Type
        </dt>
          <dd>
67
              </dd>
        <dt>
Length
            <list>
              <t>
        </dt>
<dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields. This field MUST <bcp14>MUST</bcp14> be set to 34.
              </t>
            </list>
          </t>

          <t>
              </dd>
        <dt>
Reserved

            <list>

              <t>
        </dt>
          <dd>
This field is unused for now. at the time of publication. The value MUST <bcp14>MUST</bcp14> be initialized to 0 by the sender
and MUST <bcp14>MUST</bcp14> be ignored by the receiver.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
Prefix Length
            <list>
              <t>
        </dt>
          <dd>
8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix
contained in the option.
              </t>
            </list>
          </t>

          <t>
              </dd>
        <dt>
Previous MAAR's address
            <list>
              <t> MAAR
        </dt>
          <dd>
A sixteen-octet 16-octet field containing the P-MAAR's IPv6 global address.
              </t>
            </list>
          </t>

          <t>
              </dd>
        <dt>
Home Network Prefix
            <list>
              <t>
        </dt>
          <dd>
A sixteen-octet 16-octet field containing the mobile node's MN's IPv6 Home Network Prefix. Only
the first Prefix Length bits are valid for the mobile node's MN's IPv6 Home Network
Prefix. The rest of the bits MUST <bcp14>MUST</bcp14> be ignored.
              </t>
            </list>
          </t>
              </dd>
        </dl>
      </section>
      <section anchor="subsec:smaaropt" title="Serving anchor="subsec_smaaropt" numbered="true" toc="default">
        <name>Serving MAAR Option"> Option</name>
        <t>
This new option is defined for use with the Proxy Binding Update PBU message
exchanged between the CMD and a Previous MAAR. P-MAAR. This option is used to notify the
P-MAAR about the current Serving MAAR's S-MAAR's global address. Its format is as
follows:
        </t>
        <t>
The Serving MAAR Option option has an alignment requirement of 8n+6. Its format is as
follows:
        </t>

          <figure>
            <artwork><![CDATA[
        <artwork name="" type="" align="left" 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     |     Length    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                     S-MAAR's address Address                          +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
          </figure>

          <t>Type

            <list>
              <t>
IANA-4.
              </t>
            </list>
          </t>

          <t>
<dl newline="true" spacing="normal">
        <dt>Type

        </dt>
          <dd>
68
</dd>
        <dt>
Length
            <list>
              <t>
        </dt>
          <dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields. This field MUST <bcp14>MUST</bcp14> be set to 16.
              </t>
            </list>
          </t>

          <t>
              </dd>
        <dt>
Serving MAAR's address
            <list>
              <t> MAAR
        </dt>
          <dd>
A sixteen-octet 16-octet field containing the S-MAAR's IPv6 global address.
              </t>
            </list>
          </t>
              </dd>
        </dl>
      </section>
      <section anchor="sec:dlif_link_local_format"
                 title="DLIF Link-local anchor="sec_dlif_link_local_format" numbered="true" toc="default">
        <name>DLIF Link-Local Address Option"> Option</name>
        <t>
A new DLIF Link-local Link-Local Address option is defined for use with the Proxy Binding
Acknowledgment PBA message exchanged between MAARs and between a MAAR and a CMD.
This option is used for exchanging the link-local address of the DLIF to be
configured on the serving MAAR S-MAAR so it resembles the DLIF configured on the
P-MAAR.
        </t>
        <t>
The DLIF Link-local Link-Local Address option has an alignment requirement of 8n+6. Its
format is as follows:
        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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        |    Length     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                  DLIF Link-local Link-Local Address                      +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
        <dl newline="true" spacing="normal">
        <dt>
Type

            <list>

              <t>
IANA-5.
              </t>

            </list>

          </t>

          <t>
        </dt>
          <dd>
69
              </dd>
        <dt>
Length

            <list>

              <t>

        </dt>
          <dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields. This field MUST <bcp14>MUST</bcp14> be set to 16.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
DLIF Link-local Link-Local Address

            <list>

              <t>

        </dt>
          <dd>
A sixteen-octet 16-octet field containing the link-local address of the logical interface.
              </t>

            </list>

          </t>
              </dd>
        </dl>
      </section>
      <section anchor="sec:dlif_link_layer_format"
                 title="DLIF Link-layer anchor="sec_dlif_link_layer_format" numbered="true" toc="default">
        <name>DLIF Link-Layer Address Option"> Option</name>
        <t>
A new DLIF Link-layer Link-Layer Address option is defined for use with the Proxy Binding
Acknowledgment PBA message exchanged between MAARs and betwwe between a MAAR and a CMD. This
option is used for exchanging the link-layer address of the DLIF to be
configured on the serving MAAR S-MAAR so it resembles the DLIF configured on the
P-MAAR.
        </t>
        <t>
The format of the DLIF Link-layer Link-Layer Address option is shown below. Based on the
size of the address, the option MUST <bcp14>MUST</bcp14> be aligned appropriately,
as per the mobility
option alignment requirements specified in <xref target="RFC6275" />. format="default"/>.
        </t>

<figure>
        <artwork><![CDATA[
        <artwork name="" type="" align="left" 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        |    Length     |          Reserved             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                    DLIF Link-layer Link-Layer Address                    +
.                              ...                              .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>

          <t>
        <dl newline="true" spacing="normal">
        <dt>
Type

            <list>

              <t>
IANA-6.
              </t>

            </list>

          </t>

          <t>
        </dt>
          <dd>
70
              </dd>
        <dt>
Length

            <list>

              <t>

        </dt>
          <dd>
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
Reserved

            <list>

              <t>

        </dt>
          <dd>
This field is unused for now. at the time of publication. The value MUST <bcp14>MUST</bcp14> be initialized to 0 by the sender
and MUST <bcp14>MUST</bcp14> be ignored by the receiver.
              </t>

            </list>

          </t>

          <t>
              </dd>
        <dt>
DLIF Link-layer Link-Layer Address

            <list>

              <t>
        </dt>
          <dd><t>
A variable length field containing the link-layer address of the logical
interface to be configured on the S-MAAR.
              </t>

              <t>
              </t><t>
The content and format of this field (including octet and bit ordering) is as
specified in Section 4.6 of <xref target="RFC4861" /> sectionFormat="of" section="4.6"/> for carrying link-layer
addresses. On certain access links, links where the link-layer address is not used or
cannot be determined, this option cannot be used.
              </t>

            </list>

          </t>
</t></dd>
        </dl>
      </section>
    </section>

    <!-- end of section "Message format" -->
    <section anchor="IANA" title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>
This document defines six new mobility options, the options: Anchored Prefix Option, the Prefix, Local Prefix Option, the Prefix,
Previous MAAR Option, the MAAR, Serving MAAR Option, the MAAR, DLIF
Link-local Address Option
Link-Local Address, and the DLIF Link-layer Address Option. The Link-Layer Address. IANA has assigned Type value values
for these options needs to be assigned from the same numbering space as
allocated for the other mobility options in the "Mobility Options" registry
defined in http://www.iana.org/assignments/mobility-parameters. The required
IANA actions are marked as IANA-1 to IANA-6. <eref target="http://www.iana.org/assignments/mobility-parameters"/>.
      </t>
      <t>
This document reserves a new flag (D) with a value of 0x0010 in the "Binding Update Flags"
registry and a new
flag (D) with a value of 0x02 in the "Binding Acknowledgment Flags" of the "Mobile IPv6 parameters"
registry http://www.iana.org/assignments/mobility-parameters. (<eref target="http://www.iana.org/assignments/mobility-parameters"/>).
      </t>
    </section>
    <section anchor="Security" title="Security Considerations"> numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>
The protocol extensions defined in this document share the same security
concerns of Proxy Mobile IPv6 PMIPv6 <xref target="RFC5213" />. format="default"/>. It is recommended that
the signaling messages, Proxy Binding Update PBU and Proxy Binding Acknowledgment, PBA,
exchanged between the MAARs are be protected using IPsec IPsec, specifically by using the established
security association between them. This essentially eliminates the threats
related to the impersonation of a MAAR.
      </t>
      <t>
When the CMD acts as a PBU/PBA relay, the CMD may act as a relay of a single PBU
to multiple previous MAARs. P-MAARs. In situations of with many fast handovers (e.g., with
vehicular networks), there may exist multiple previous (e.g., k) MAARs. MAARs may exist. In this
situation, the CMD creates k outgoing packets from a single incoming packet.
This bears a certain amplification risk. The CMD MUST <bcp14>MUST</bcp14> use a pacing approach in
the outgoing queue to cap the output traffic (i.e., the rate of PBUs sent) to
limit this amplification risk.
      </t>
      <t>
When the CMD acts as a MAAR locator, mobility signaling (PBAs) is exchanged
between P-MAARs and the current S-MAAR. Hence, security associations are REQUIRED <bcp14>REQUIRED</bcp14> to
exist between the involved MAARs (in addition to the ones needed with the CMD).
      </t>
      <t>
Since deregistration de-registration is performed by timeout, measures SHOULD <bcp14>SHOULD</bcp14> be implemented to
minimize the risks associated to with continued resource consumption (DoS attacks),
e.g., imposing a limit of on the number of P-MAARs associated to with a given MN.
      </t>
      <t>
The CMD and the participating MAARs MUST <bcp14>MUST</bcp14> be trusted parties, parties authorized perform
all operations relevant to their role.
      </t>
      <t>
There are some privacy considerations to consider. While the involved parties
trust each other, the signalling signaling involves disclosing information about the
previous locations visited by each MN, as well as the active prefixes they are
using at a given point of time. Therefore, mechanisms MUST <bcp14>MUST</bcp14> be in place to ensure
that MAARs and CMD CMDs do not disclose this information to other parties nor or use it
for other ends that than providing the distributed mobility support specified in this
document.
      </t>
    </section>
  </middle>
  <back>

<displayreference target="I-D.bernardos-dmm-distributed-anchoring" to="DISTRIBUTED-ANCHORING"/>
<displayreference target="I-D.bernardos-dmm-pmip" to="DMM-PMIP"/>

    <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.6275.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5213.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4191.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4861.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7333.xml"/>
      </references>
      <references>
        <name>Informative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7429.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8563.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6724.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.bernardos-dmm-distributed-anchoring.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.bernardos-dmm-pmip.xml"/>

      </references>
    </references>
    <section anchor="Acknowledgments" title="Acknowledgments"> numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>
The authors would like to thank Dirk <contact fullname="Dirk von Hugo, John Kaippallimalil, Ines Robles,
Joerg Ott, Carlos Pignataro, Vincent Roca, Mirja K&uuml;hlewind, &Eacute;ric
Vyncke, Adam Roach, Benjamin Kaduk and Roman Danyliw Hugo"/>, <contact fullname="John Kaippallimalil"/>, <contact fullname="Ines Robles"/>,
<contact fullname="Joerg Ott"/>, <contact fullname="Carlos Pignataro"/>, <contact fullname="Vincent Roca"/>, <contact fullname="Mirja Kühlewind"/>, <contact fullname="Éric
Vyncke"/>, <contact fullname="Adam Roach"/>, <contact fullname="Benjamin Kaduk"/>, and <contact fullname="Roman Danyliw"/> for the comments on this
document. The authors would also like to thank Marco Liebsch, Dirk <contact fullname="Marco Liebsch"/>, <contact fullname="Dirk von Hugo,
Alex Petrescu, Daniel Corujo, Akbar Rahman, Danny Moses, Xinpeng Wei and Satoru
Matsushima Hugo"/>,
<contact fullname="Alex Petrescu"/>, <contact fullname="Daniel Corujo"/>, <contact fullname="Akbar Rahman"/>, <contact fullname="Danny Moses"/>, <contact fullname="Xinpeng Wei"/>, and <contact fullname="Satoru
Matsushima"/> for their comments and discussion on the documents <xref target="I-D.bernardos-dmm-distributed-anchoring" /> format="default"/> and <xref target="I-D.bernardos-dmm-pmip" /> format="default"/>, on which the present document is based.
      </t>
      <t>
The authors would also like to thank Lyle Bertz and Danny Moses <contact fullname="Lyle Bertz"/> and <contact fullname="Danny Moses"/> for their
in-deep
in-depth review of this document and their very valuable comments and
suggestions.
      </t>
    </section>

  </middle>

  <back>
    <references title="Normative References">

      &rfc2119;
      &rfc8174;
      &rfc6275;
      &rfc5213;
      &rfc4191;
      &rfc4861;
      &rfc7333;

    </references>

    <references title="Informative References">

      &rfc7429;
      &rfc8563;
      &I-D.bernardos-dmm-distributed-anchoring;
      &I-D.bernardos-dmm-pmip;

    </references>

    <!---->
  </back>
</rfc>