One document matched: draft-ietf-dmm-best-practices-gap-analysis-07.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!--
<!ENTITY RFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
-->
<!ENTITY RFC6275 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6275.xml">
<!ENTITY RFC5213 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5213.xml">
<!ENTITY RFC5555 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5555.xml">
<!ENTITY RFC5844 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5844.xml">
<!ENTITY RFC3963 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3963.xml">
<!ENTITY RFC4640 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4640.xml">
<!ENTITY RFC5026 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5026.xml">
<!ENTITY RFC6611 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6611.xml">
<!ENTITY RFC4225 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4225.xml">
<!ENTITY RFC5380 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5380.xml">
<!ENTITY RFC5142 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5142.xml">
<!ENTITY RFC6705 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6705.xml">
<!ENTITY RFC6463 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6463.xml">
<!ENTITY RFC6097 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6097.xml">
<!ENTITY RFC4555 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4555.xml">
<!ENTITY RFC5996 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5996.xml">
<!ENTITY RFC5014 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5014.xml">
<!ENTITY RFC6224 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6224.xml">
<!ENTITY RFC7028 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7028.xml">
<!ENTITY RFC4889 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4889.xml">
<!ENTITY RFC5568 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5568.xml">
<!ENTITY RFC4066 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4066.xml">
<!ENTITY RFC4067 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4067.xml">
<!ENTITY RFC6697 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6697.xml">
<!ENTITY RFC4960 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4960.xml">
<!ENTITY RFC6724 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6724.xml">
<!ENTITY RFC4295 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4295.xml">
<!ENTITY RFC6020 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6020.xml">
<!ENTITY RFC6241 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6241.xml">
<!ENTITY RFC6475 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6475.xml">
<!ENTITY RFC7333 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7333.xml">
<!ENTITY I-D.gundavelli-v6ops-community-wifi-svcs SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.gundavelli-v6ops-community-wifi-svcs">
<!ENTITY I-D.bhandari-dhc-class-based-prefix SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.bhandari-dhc-class-based-prefix.xml">
<!ENTITY I-D.korhonen-6man-prefix-properties SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.korhonen-6man-prefix-properties.xml">
<!ENTITY I-D.anipko-mif-mpvd-arch SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.anipko-mif-mpvd-arch.xml">
<!ENTITY I-D.ietf-netext-pmip-cp-up-separation SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-netext-pmip-cp-up-separation.xml">
<!ENTITY TS29060 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.29.060.xml">
<!ENTITY TS23859 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.23.859.xml">
<!ENTITY TR29281 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.29.281.xml">
<!ENTITY TS29274 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.29.274.xml">
<!ENTITY TS23402 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.23.402.xml">
<!ENTITY TS23401 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.23.401.xml">
<!ENTITY TS29303 SYSTEM "http://xml.resource.org/public/rfc/bibxml5/reference.SDO-3GPP.29.303.xml">
]>
<!-- give errors regarding ID-nits and DTD validation -->
<!-- control the table of contents (ToC) -->
<?rfc toc="yes"?>
<!-- generate a ToC -->
<?rfc symrefs="yes"?>
<!-- use symbolic references tags, i.e, [RFC2119] instead of [1] -->
<?rfc sortrefs="yes"?>
<!-- sort the reference entries alphabetically -->
<?rfc iprnotified="no"?>
<?rfc compact="yes" ?>
<!-- do not start each main section on a new page -->
<?rfc subcompact="no" ?>
<!-- keep one blank line between list items -->
<rfc category="info" ipr="trust200902" docName="draft-ietf-dmm-best-practices-gap-analysis-07">
<!-- category values: std, bcp, info, exp, and historic
ipr values: full3667, noModification3667, noDerivatives3667
you can add the attributes updates="NNNN" and obsoletes="NNNN"
they will automatically be output with "(if approved)" -->
<!-- ***** FRONT MATTER ***** -->
<front>
<!-- The abbreviated title is used in the page header- it is only
necessary if the full title is longer than 39 characters -->
<title abbrev="DMM-best-practices-gap-analysis">
Distributed Mobility Management: Current practices and gap analysis
</title>
<author initials="D" role="editor" surname="Liu" fullname="Dapeng Liu">
<organization>China Mobile</organization>
<address>
<postal>
<street>Unit2, 28 Xuanwumenxi Ave, Xuanwu District</street>
<city>Beijing</city>
<code>100053</code>
<country>China</country>
</postal>
<email>liudapeng@chinamobile.com</email>
</address>
</author>
<author initials="JC." role="editor" surname="Zuniga" fullname="Juan Carlos Zuniga">
<organization abbrev="InterDigital">InterDigital Communications, LLC</organization>
<address>
<postal>
<street>1000 Sherbrooke Street West, 10th floor</street>
<city>Montreal, Quebec</city>
<code> H3A 3G4</code>
<country>Canada</country>
</postal>
<email>JuanCarlos.Zuniga@InterDigital.com</email>
<uri>http://www.InterDigital.com/</uri>
</address>
</author>
<author initials="P" surname="Seite" fullname="Pierrick Seite">
<organization>Orange</organization>
<address>
<postal>
<street>4, rue du Clos Courtel, BP 91226</street>
<city>Cesson-Sevigne</city>
<code>35512</code>
<country>France</country>
</postal>
<email>pierrick.seite@orange.com</email>
</address>
</author>
<author initials="H" surname="Chan" fullname="H Anthony Chan">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>5340 Legacy Dr. Building 3</street>
<city>Plano, TX</city>
<code>75024</code>
<country>USA</country>
</postal>
<email>h.a.chan@ieee.org</email>
</address>
</author>
<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>
<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>
<date month="September" year="2014"></date>
<!-- If the month and year are both specified and are the current ones,
xml2rfc will fill in the current day for you. If only the current
year is specified, xml2rfc will fill in the current day and month
for you. If the year is not the current one, it is necessary to
specify at least a month (xml2rfc assumes day="1" if not specified
for the purpose of calculating the expiry date). With drafts it is
normally sufficient to specify just the year. -->
<!-- Meta-data Declarations -->
<area>Internet</area>
<workgroup>DMM</workgroup>
<abstract>
<t>
<!-- TODO: needs to be extended -->
This document analyzes deployment practices of existing IP mobility
protocols in a distributed mobility management environment. It then identifies
existing limitations when compared to the requirements defined for a distributed
mobility management solution.
</t>
</abstract>
</front>
<middle>
<!-- BEGIN 1. Introduction -->
<section anchor="sec:intro" title="Introduction">
<t>
The centralized deployment of mobility anchors to manage IP sessions pose several
problems. In order to address these problems, a distributed mobility management (DMM)
architecture has been proposed. This document investigates whether it is feasible to deploy current IP mobility
protocols in a DMM scenario in a way that can fulfill the requirements as
defined in <xref target="RFC7333" />. It discusses current
deployment practices of existing mobility protocols and identifies the
limitations (gaps) in these practices from the standpoint of satisfying DMM
requirements.
</t>
<t>
The rest of this document is organized as follows. <xref
target="sec:mobility_mngnt_functions" /> analyzes existing IP mobility protocols
by examining their functions and how these functions can be configured and used
to work in a DMM environment. <xref target="sec:practices" /> presents the
current practices of IP wireless networks and 3GPP architectures. Both
network- and host-based mobility protocols are considered.
<xref target="sec:gap" /> presents the gap analysis with respect to the current
practices.
</t>
</section>
<!-- END 1. Introduction -->
<!-- BEGIN 2. Terminology -->
<section anchor="sec:terminology" title="Terminology">
<!--
<t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described
in <xref target="RFC2119" />.
</t>
-->
<t>
All general mobility-related terms and their acronyms used in this document are
to be interpreted as defined in the Mobile IPv6 base specification
<xref target="RFC6275" />, in the Proxy mobile IPv6 specification
<xref target="RFC5213" />,
and in the Distributed Management Requirements
<xref target="RFC7333" />. These terms include mobile node (MN), correspondent
node (CN), home agent (HA), local mobility anchor (LMA), mobile access
gateway (MAG),
centrally depoyed mobility anchors,
distributed mobility management,
hierarchical mobile network,
flatter mobile network,
and
flattening mobile network.
</t>
<t>
In addition, this document also introduces some definitions of IP mobility
functions in <xref target="sec:mobility_mngnt_functions" />.
</t>
<t>
In this document there are also references to a "distributed mobility management
environment". By this term, we refer to a scenario in which the IP mobility,
access network and routing solutions allow for setting up IP networks
so that traffic is distributed in an optimal way, without the reliance on
centrally deployed mobility anchors to manage IP mobility sessions.
</t>
</section>
<!-- END 2. Terminology -->
<!-- BEGIN 3. Functions of existing mobility protocols -->
<section anchor="sec:mobility_mngnt_functions" title="Functions of existing mobility protocols">
<t>
The host-based Mobile IPv6 (MIPv6) <xref target="RFC6275"/> and its
network-based extension, Proxy Mobile IPv6 (PMIPv6) <xref target="RFC5213"/>,
even Hierarchical Mobile IPv6 (HMIPv6) <xref target="RFC5380"/> are logically
centralized mobility management approaches addressing primarily hierarchical
mobile networks. Although these two are centralized approaches, they have
important mobility management functions resulting from years of extensive work
to develop and to extend these functions. It is therefore useful to take these
existing functions and examine them in a DMM scenario in order to understand how
to deploy the existing mobility protocols to provide distributed mobility
management.
</t>
<t>
The main mobility management functions of MIPv6, PMIPv6, and HMIPv6 are the
following:
<list style="numbers">
<t>
Anchoring function (AF): allocation to a mobile node of an IP address (a Home
Address, HoA) or prefix (a Home Network Prefix, HNP) topologically anchored by
the advertising node (i.e., the anchor node is able to advertise a connected
route into the routing infrastructure for the allocated IP prefixes). It is a
control plane function.
<vspace blankLines="1" />
</t>
<t>
Internetwork Location Information (LI) function: managing and keeping track of
the internetwork location of an MN. The location information may be a binding of
the IP advertised address/prefix (e.g., HoA or HNP) to the IP routing address of
the MN or of a node that can forward packets destined to the MN. It is a control
plane function.
<vspace blankLines="1" />
In a client-server protocol model, location query and update messages may be
exchanged between a location information client (LIc) and a location information
server (LIs).
<vspace blankLines="1" />
</t>
<t>
Forwarding Management (FM) function: packet interception and forwarding to/from
the IP address/prefix assigned to the MN, based on the internetwork location
information, either to the destination or to some other network element that
knows how to forward the packets to their destination.
<vspace blankLines="1" />
FM may optionally be split into the control plane (FM-CP) and data plane
(FM-DP).
<vspace blankLines="1" />
</t>
</list>
</t>
<t>
In Mobile IPv6, the home agent (HA) typically provides the anchoring function
(AF); the location information server (LIs) is at the HA while the location
information client (LIc) is at the MN; the forwarding management (FM) function
is both ends of tunneling at the HA and the MN.
</t>
<t>
In Proxy Mobile IPv6, the Local Mobility Anchor (LMA) provides the anchoring
function (AF); the location information server (LIs) is at the LMA while the
location information client (LIc) is at the mobile access gateway (MAG); the
forwarding management (FM) function is both ends of tunneling at the HA and the
MAG.
</t>
<t>
In Hierarchical Mobile IPv6 (HMIPv6) <xref target="RFC5380"/>, the mobility
anchor point (MAP) serves as a location information aggregator between the LIs
at the HA and the LIc at the MN. The MAP also has FM function to enable
tunneling between HA and itself as well as tunneling between MN and itself.
</t>
</section>
<!-- END 3. Functions of existing mobility protocols -->
<!-- BEGIN 4. DMM practices -->
<section anchor="sec:practices" title="DMM practices">
<t>
This section documents deployment practices of existing mobility protocols to
satisfy distributed mobility management requirements. This description considers
both IP wireless (e.g., evolved Wi-Fi hotspots) and 3GPP flattening mobile network.
</t>
<t>
While describing the current DMM practices, references to the generic mobility
management functions described in <xref target="sec:mobility_mngnt_functions" />
are provided, as well as some initial hints on the identified gaps with respect
to the DMM requirements documented in
<xref target="RFC7333" />.
</t>
<!-- BEGIN 4.1 Assumptions -->
<section anchor="sec:assumptions" title="Assumptions">
<t>
There are many different approaches that can be considered to implement and
deploy a distributed anchoring and mobility solution. The focus of the gap
analysis is on certain current mobile network architectures and standardized IP
mobility solutions, considering any kind of deployment options which do not
violate the original protocol specifications. In order to limit the scope of our
analysis of DMM practices, we consider the following list of technical
assumptions:
<list style="numbers">
<t>
Both host- and network-based solutions are considered.
</t>
<t>
Solutions should allow selecting and using the most appropriate IP anchor among
a set of available candidates.
</t>
<t>
Mobility management should be realized by the preservation of the IP address
across the different points of attachment (i.e., provision of IP address
continuity). This is in contrast to certain transport-layer based approaches
such as Stream Control Transmission Protocol (SCTP) <xref target="RFC4960" />
or application-layer mobility.
</t>
</list>
Applications which can cope with changes in the MN's IP address do not
depend on IP mobility management protocols such as DMM. Typically, a connection
manager together with the operating system will configure the source address
selection mechanism of the IP stack. This might involve identifying application
capabilities and triggering the mobility support accordingly. Further
considerations on application management and source address selection are out
of the scope of this document, but the reader might consult
<xref target="RFC6724" />.
</t>
</section>
<!-- END 4.1 Assumptions -->
<!-- BEGIN 4.2. IP flat wireless network -->
<section anchor="sec:IP_flat_wireless" title="IP flat wireless network">
<t>
This section focuses on common IP wireless network architectures and how they
can be flattened from an IP mobility and anchoring point of view using common
and standardized protocols. We take Wi-Fi as an useful wireless technology,
since it is widely known and deployed nowadays. Some representative examples of
Wi-Fi deployment architectures are depicted in <xref target="fig:Wi-Fi_arch" />.
</t>
<figure anchor="fig:Wi-Fi_arch" title="IP Wi-Fi network architectures" >
<artwork><![CDATA[
+-------------+ _----_
+---+ | Access | _( )_
|AAA|. . . . . . | Aggregation |----------( Internet )
+---+ | Gateway | (_ _)
+-------------+ '----'
| | |
| | +-------------+
| | |
| | +-----+
+---------------+ | | AR |
| | +--+--+
+-----+ +-----+ *----+----*
| RG | | WLC | ( LAN )
+-----+ +-----+ *---------*
. / \ / \
/ \ +-----+ +-----+ +-----+ +-----+
/ \ |Wi-Fi| |Wi-Fi| |Wi-Fi| |Wi-Fi|
MN1 MN2 | AP1 | | AP2 | | AP3 | | AP4 |
+-----+ +-----+ +-----+ +-----+
. .
/ \ / \
/ \ / \
MN3 MN4 MN5 MN6
]]></artwork>
</figure>
<t>
In the figure, three typical deployment options are shown <xref
target="I-D.gundavelli-v6ops-community-wifi-svcs" />. On the left hand side of
the figure, mobile nodes MN1 and MN2 directly connect to a Residential Gateway
(RG) which is a network device at the customer premises and provides both
wireless layer-2 access connectivity (i.e., it hosts the 802.11 Access Point
function) and layer-3 routing functions. In the middle of the figure, mobile
nodes MN3 and MN4 connect to Wi-Fi Access Points (APs) AP1 and AP2 that are
managed by a WLAN Controller (WLC), which performs radio resource management on
the APs, domain-wide mobility policy enforcement and centralized forwarding
function for the user traffic. The WLC could also implement layer-3 routing
functions, or attach to an access router (AR). Last, on the right-hand side of
the figure, access points AP3 and AP4 are directly connected to an access
router. This can also be used as a generic connectivity model.
</t>
<t>
IP mobility protocols can be used to provide inter-access mobility support to
users, e.g., handover from Wi-Fi to cellular access. Two kind of protocols can
be used: Proxy Mobile IPv6 <xref target="RFC5213" /> or Mobile IPv6
<xref target="RFC5555" />, with the mobility anchor (e.g., local mobility anchor
or home agent) role typically being played by the edge router of the mobile
network <xref target="SDO-3GPP.23.402" />.
</t>
<t>
Although this section has made use of the example of Wi-Fi networks, there are
other IP flat wireless network architectures specified, such as WiMAX
<xref target="IEEE.802-16.2009" />, which integrates both host and
network-based IP mobility functionality.
</t>
<t>
Existing IP mobility protocols can also be deployed in a flatter manner,
so that the anchoring and access aggregation functions are distributed. We next
describe several practices for the deployment of existing mobility protocols in
a distributed mobility management environment. The analysis in this section is
limited to protocol solutions based on existing IP mobility protocols, either
host- or network-based, such as Mobile IPv6 <xref target="RFC6275" />,
<xref target="RFC5555" />, Proxy Mobile IPv6 (PMIPv6) <xref target="RFC5213" />, <xref
target="RFC5844" /> and Network Mobility Basic Support protocol (NEMO)
<xref target="RFC3963" />. Extensions to these base protocol solutions are also
considered. The analysis is divided into two parts: host- and network-based
practices.
</t>
<!-- BEGIN 4.2.1. Host-based IP DMM practices -->
<section anchor="sec:host_dmm" title="Host-based IP DMM practices">
<t>
Mobile IPv6 (MIPv6) <xref target="RFC6275"/> and its extension to support mobile
networks, the NEMO Basic Support protocol (hereafter, simply referred to as
NEMO) <xref target="RFC3963"/> are well-known host-based IP mobility protocols.
They depend upon the function of the Home Agent (HA), a centralized anchor, to
provide mobile nodes (hosts and routers) with mobility support. In these
approaches, the home agent typically provides the anchoring function (AF),
forwarding management (FM), and Internetwork Location Information server (LIs)
functions. The mobile node possesses the Location Information client (LIc)
function and the FM function to enable tunneling between HA and itself. We next
describe some practices that show how MIPv6/NEMO and several other protocol
extensions can be deployed in a distributed mobility management environment.
</t>
<t>
One approach to distribute the anchors can be to deploy several HAs (as shown in
<xref target="fig-MIPv6_multiple_HAs"/>), and assign the topologically closest
anchor to each MN <xref target="RFC4640"/>, <xref target="RFC5026"/>,
<xref target="RFC6611"/>. In the example shown in
<xref target="fig-MIPv6_multiple_HAs"/>, MN1 is assigned HA1 (and a home address
anchored by HA1), while MN2 is assigned HA2. Note that MIPv6/NEMO
specifications do not prevent the simultaneous use of multiple home agents by a
single mobile node. In this deployment model, the mobile node can use several
anchors at the same time, each of them anchoring IP flows initiated at a
different point of attachment. However there is no mechanism specified to enable
an efficient dynamic discovery of available anchors and the selection of the
most suitable one. Note that some of these mechanisms
<xref target="SDO-3GPP.23.402"/> have been defined in other standards
organizations.
</t>
<figure anchor="fig-MIPv6_multiple_HAs" align="center"
title="Distributed operation of Mobile IPv6 (BT and RO) / NEMO">
<artwork><![CDATA[
<- INTERNET -> <- HOME NETWORK -> <---- ACCESS NETWORK ---->
------- -------
| CN1 | ------- | AR1 |-(o) zzzz (o)
------- | HA1 | ------- |
------- (MN1 anchored at HA1) -------
------- | MN1 |
| AR2 |-(o) -------
-------
-------
| HA2 | -------
------- | AR3 |-(o) zzzz (o)
------- |
------- (MN2 anchored at HA2) -------
| CN2 | ------- | MN2 |
------- | AR4 |-(o) -------
-------
CN1 CN2 HA1 HA2 AR1 MN1 AR3 MN2
| | | | | | | |
|<------------>|<=================+=====>| | | BT mode
| | | | | | | |
| |<----------------------------------------+----->| RO mode
| | | | | | | |
]]></artwork>
</figure>
<t>
Since one of the goals of the deployment of mobility protocols in a distributed
mobility management environment is to avoid the suboptimal routing caused by
centralized anchoring, the Route Optimization (RO) support provided by Mobile
IPv6 can also be used to achieve a flatter IP data forwarding. By default,
Mobile IPv6 and NEMO use the so-called Bidirectional Tunnel (BT) mode, in which
data traffic is always encapsulated between the MN and its HA before being
directed to any other destination. The Route Optimization (RO) mode allows the
MN to update its current location on the CNs, and then use the direct path
between them. Using the example shown in <xref
target="fig-MIPv6_multiple_HAs"/>, MN1 is using BT mode with CN1 and MN2 is in
RO mode with CN2. However, the RO mode has several drawbacks:
<list style="symbols">
<t>
The RO mode is only supported by Mobile IPv6. There is no route optimization
support standardized for the NEMO protocol because of the security problems
posed by extending return routability tests for prefixes, although many
different solutions have been proposed <xref target="RFC4889"/>.
</t>
<t>
The RO mode requires signaling that adds some protocol overhead.
</t>
<t>
The signaling required to enable RO involves the home agent and is repeated
periodically for security reasons <xref target="RFC4225"/> and, thus, the HA
remains a single point of failure.
</t>
<t>
The RO mode requires support from the correspondent node (CN).
</t>
</list>
</t>
<t>
Notwithstanding these considerations, the RO mode does offer the possibility
of substantially reducing traffic through the Home Agent, in cases when it can
be supported by the relevant correspondent nodes. Note that a mobile node can
also use its CoA directly <xref target="RFC5014" /> when communicating with CNs
on the same link or anywhere in the Internet, although no session continuity
support would be provided by the IP stack in this case.
</t>
<t>
Hierarchical Mobile IPv6 (HMIPv6) <xref target="RFC5380"/> (as shown in
<xref target="fig-MIPv6_HMIPv6"/>), is another host-based IP mobility extension
which can be considered as a complement to provide a less centralized mobility
deployment. It allows reducing the amount of mobility signaling as well as
improving the overall handover performance of Mobile IPv6 by introducing a new
hierarchy level to handle local mobility. The Mobility Anchor Point (MAP) entity
is introduced as a local mobility handling node deployed closer to the mobile
node. It provides LI intermediary function between the LI server (LIs) at the HA
and the LI client (LIc) at the MN. It also performs the FM function using
tunneling with the HA and also to tunnel with the MN.
</t>
<figure anchor="fig-MIPv6_HMIPv6" title="Hierarchical Mobile IPv6"
align="center">
<artwork><![CDATA[
<- INTERNET -> <- HOME NETWORK -> <------- ACCESS NETWORK ------->
-----
/|AR1|-(o) zz (o)
-------- / ----- |
| MAP1 |< -------
-------- \ ----- | MN1 |
------- \|AR2| -------
| CN1 | ----- HoA anchored
------- ----- at HA1
------- /|AR3| RCoA anchored
| HA1 | -------- / ----- at MAP1
------- | MAP2 |< LCoA anchored
-------- \ ----- at AR1
\|AR4|
------- -----
| CN2 | -----
------- /|AR5|
-------- / -----
| MAP3 |<
-------- \ -----
\|AR6|
-----
CN1 CN2 HA1 MAP1 AR1 MN1
| | | | ________|__________ |
|<------------------>|<==============>|<________+__________>| HoA
| | | | | |
| |<-------------------------->|<===================>| RCoA
| | | | | |
]]></artwork>
</figure>
<t>
When HMIPv6 is used, the MN has two different temporary addresses: the Regional
Care-of Address (RCoA) and the Local Care-of Address (LCoA). The RCoA is
anchored at one MAP, that plays the role of local home agent, while the LCoA is
anchored at the access router level. The mobile node uses the RCoA as the CoA
signaled to its home agent. Therefore, while roaming within a local domain
handled by the same MAP, the mobile node does not need to update its home agent
(i.e., the mobile node does not change its RCoA).
</t>
<t>
The use of HMIPv6 enables some form of route optimization, since a mobile node
may decide to directly use the RCoA as source address for a communication with a
given correspondent node, particularly if the MN does not expect to move outside
the local domain during the lifetime of the communication. This can be seen as a
potential DMM mode of operation,though it fails to provide session continuity if
and when the MN moves outside the local domain. In the example shown in
<xref target="fig-MIPv6_HMIPv6"/>, MN1 is using its global HoA to communicate
with CN1, while it is using its RCoA to communicate with CN2.
</t>
<t>
Furthermore, a local domain might have several MAPs deployed, enabling therefore
a different kind of HMIPv6 deployments (e.g., flattening and distributed). The HMIPv6
specification supports a flexible selection of the MAP (e.g., based on the
distance between the MN and the MAP, taking into consideration the expected
mobility pattern of the MN, etc.).
</t>
<t>
Another extension that can be used to help distributing mobility management
functions is the Home Agent switch specification <xref target="RFC5142"/>, which
defines a new mobility header for signaling a mobile node that it should acquire
a new home agent. <xref target="RFC5142"/> does not specify the case of changing
the mobile node's home address, as that might imply loss of connectivity for
ongoing persistent connections. Nevertheless, that specification could be used
to force the change of home agent in those situations where there are no active
persistent data sessions that cannot cope with a change of home address.
</t>
<t>
There are other host-based approaches standardized that can be used to provide
mobility support. For example MOBIKE <xref target="RFC4555" /> allows a mobile
node encrypting traffic through IKEv2 <xref target="RFC5996" /> to change its
point of attachment while maintaining a Virtual Private Network (VPN) session.
The MOBIKE protocol allows updating the VPN Security Associations (SAs) in cases
where the base connection initially used is lost and needs to be re-established.
The use of the MOBIKE protocol avoids having to perform an IKEv2 re-negotiation.
Similar considerations to those made for Mobile IPv6 can be applied to MOBIKE;
though MOBIKE is best suited for situations where the address of at least one
endpoint is relatively stable and can be discovered using existing mechanisms
such as DNS.
</t>
<t>
Extensions have been defined to the mobility protocol to optimize the handover
performance. Mobile IPv6 Fast Handovers (FMIPv6) <xref target="RFC5568"/> is
the extension to optimize handover latency. It defines new access router
discovery mechanism before handover to reduce the new network discovery latency.
It also defines a tunnel between the previous access router and the new access
router to reduce the packet loss during handover. The Candidate Access Router
Discovery (CARD) <xref target="RFC4066"/> and Context Transfer Protocol (CXTP)
<xref target="RFC4067"/> protocols were standardized to improve the handover
performance. The DMM deployment practice discussed in this section can also use
those extensions to improve the handover performance.
</t>
</section>
<!-- END 4.2.1. Host-based IP DMM practices -->
<!-- BEGIN 4.2.2. Network-based IP DMM practices -->
<section anchor="sec:net_dmm" title="Network-based IP DMM practices">
<t>
Proxy Mobile IPv6 (PMIPv6) <xref target="RFC5213"/> is the main network-based IP
mobility protocol specified for IPv6. Proxy Mobile IPv4 <xref target="RFC5844"/>
defines some IPv4 extensions. With network-based IP mobility protocols, the
local mobility anchor (LMA) typically provides the anchoring function (AF),
Forwarding management (FM) function, and Internetwork Location Information
server (LIs) function. The mobile access gateway (MAG) provides the Location
Information client (LIc) function and Forwarding management (FM) function to
tunnel with LMA. PMIPv6 is architecturally almost identical to MIPv6, as the
mobility signaling and routing between LMA and MAG in PMIPv6 is similar to those
between HA and MN in MIPv6. The required mobility functionality at the MN is
provided by the MAG so that the involvement in mobility support by the MN is not
required.
</t>
<t>
We next describe some practices that show how network-based mobility protocols
and several other protocol extensions can be deployed in a distributed mobility
management environment.
</t>
<t>
One way to decentralize Proxy Mobile IPv6 operation can be to deploy several
local mobility anchors and use some selection criteria to assign LMAs to
attaching mobile nodes (an example of this type of assignment is shown in
<xref target="fig-PMIPv6_multiple_LMAs"/>). As with the client based approach, a
mobile node may use several anchors at the same time, each of them anchoring IP
flows initiated at a different point of attachment. This assignment can be
static or dynamic. The main advantage of this simple approach is that the IP
address anchor (i.e., the LMA) could be placed closer to the mobile node.
Therefore the resulting paths are close-to-optimal. On the other hand, as soon
as the mobile node moves, the resulting path will start deviating from the
optimal one.
</t>
<figure anchor="fig-PMIPv6_multiple_LMAs" align="center"
title="Distributed operation of Proxy Mobile IPv6">
<artwork><![CDATA[
<- INTERNET -><- HOME NET -><----------- ACCESS NETWORK ------------>
-------
| CN1 | -------- -------- --------
------- -------- | MAG1 | | MAG2 | | MAG3 |
| LMA1 | ---+---- ---+---- ---+----
------- -------- | | |
| CN2 | (o) (o) (o)
------- -------- x x
| LMA2 | x x
------- -------- (o) (o)
| CN3 | | |
------- ---+--- ---+---
Anchored | MN1 | Anchored | MN2 |
at LMA1 -> ------- at LMA2 -> -------
CN1 CN2 LMA1 LMA2 MAG1 MN1 MAG3 MN2
| | | | | | | |
|<------------>|<================>|<---->| | |
| | | | | | | |
| |<------------>|<========================>|<----->|
| | | | | | | |
]]></artwork>
</figure>
<t>
Similar to the host-based IP mobility case,
network-based IP mobility has some extensions defined to mitigate the
suboptimal routing issues that may arise due to the use of a centralized
anchor.
The Local Routing extensions <xref target="RFC6705"/> enable optimal
routing in Proxy Mobile IPv6 in three cases: i) when two communicating MNs are
attached to the same MAG and LMA, ii) when two communicating MNs are attached to
different MAGs but to the same LMA, and iii) when two communicating MNs are
attached to the same MAG but have different LMAs. In these three cases, data
traffic between the two mobile nodes does not traverse the LMA(s), thus
providing some form of path optimization since the traffic is locally routed at
the edge. The main disadvantage of this approach is that it only tackles the
MN-to-MN communication scenario, and only under certain circumstances.
</t>
<t>
An interesting extension that can also be used to facilitate the deployment of
network-based mobility protocols in a distributed mobility management
environment is the LMA runtime assignment <xref target="RFC6463"/>. This
extension specifies a runtime local mobility anchor assignment functionality
and corresponding mobility options for Proxy Mobile IPv6. This runtime local
mobility anchor assignment takes place during the Proxy Binding Update / Proxy
Binding Acknowledgment message exchange between a mobile access gateway and a
local mobility anchor. While this mechanism is mainly aimed for load-balancing
purposes, it can also be used to select an optimal LMA from the routing point of
view. A runtime LMA assignment can be used to change the assigned LMA of an MN,
for example, in cases when the mobile node does not have any active session, or
when the running sessions can survive an IP address change. Note that several
possible dynamic local mobility anchor discovery solutions can be used, as
described in <xref target="RFC6097"/>.
</t>
</section>
<!-- END 4.2.2. Network-based IP DMM practices -->
</section>
<!-- END 4.2. IP flat wireless network -->
<!-- BEGIN 4.3. flattening 3GPP mobile network approaches-->
<section anchor="sec:3gpp" title="Flattening 3GPP mobile network approaches">
<t>
The 3rd Generation Partnership Project (3GPP) is the standards development
organization that specifies the 3rd generation mobile network and the Evolved
Packet System (EPS), which mainly comprises the Evolved Packet Core (EPC) and a
new radio access network, usually referred to as LTE (Long Term Evolution).
</t>
<t>
Architecturally, the 3GPP Evolved Packet Core (EPC) network is similar to an IP
wireless network running PMIPv6 or MIPv6, as it relies on the Packet Data
Gateway (PGW) anchoring services to provide mobile nodes with mobility support
(see <xref target="fig:eps_arch" />). There are client-based and network-based
mobility solutions in 3GPP, which for simplicity will be analyzed together. We
next describe how 3GPP mobility protocols and several other completed or
ongoing extensions can be deployed to meet some of the DMM requirements <xref target="RFC7333" />.
</t>
<figure anchor="fig:eps_arch" title="EPS (non-roaming) architecture
overview" >
<artwork><![CDATA[
+---------------------------------------------------------+
| PCRF |
+-----------+--------------------------+----------------+-+
| | |
+----+ +-----------+------------+ +--------+-----------+ +-+-+
| | | +-+ | | Core Network | | |
| | | +------+ |S|__ | | +--------+ +---+ | | |
| | | |GERAN/|_|G| \ | | | HSS | | | | | |
| +-----+ UTRAN| |S| \ | | +---+----+ | | | | E |
| | | +------+ |N| +-+-+ | | | | | | | x |
| | | +-+ /|MME| | | +---+----+ | | | | t |
| | | +---------+ / +---+ | | | 3GPP | | | | | e |
| +-----+ E-UTRAN |/ | | | AAA | | | | | r |
| | | +---------+\ | | | SERVER | | | | | n |
| | | \ +---+ | | +--------+ | | | | a |
| | | 3GPP AN \|SGW+----- S5---------------+ P | | | l |
| | | +---+ | | | G | | | |
| | +------------------------+ | | W | | | I |
| UE | | | | | | P |
| | +------------------------+ | | +-----+ |
| | |+-------------+ +------+| | | | | | n |
| | || Untrusted +-+ ePDG +-S2b---------------+ | | | e |
| +---+| non-3GPP AN | +------+| | | | | | t |
| | |+-------------+ | | | | | | w |
| | +------------------------+ | | | | | o |
| | | | | | | r |
| | +------------------------+ | | | | | k |
| +---+ Trusted non-3GPP AN +-S2a--------------+ | | | s |
| | +------------------------+ | | | | | |
| | | +-+-+ | | |
| +--------------------------S2c--------------------| | | |
| | | | | |
+----+ +--------------------+ +---+
]]></artwork>
</figure>
<t>
The GPRS Tunneling Protocol (GTP) <xref target="SDO-3GPP.29.060"/>
<xref target="SDO-3GPP.29.281"/> <xref target="SDO-3GPP.29.274"/> is a
network-based mobility protocol specified for 3GPP networks (S2a, S2b, S5 and S8
interfaces). Similar to PMIPv6, it can handle mobility without requiring the
involvement of the mobile nodes. In this case, the mobile node functionality is
provided in a proxy manner by the Serving Data Gateway (SGW), Evolved Packet
Data Gateway (ePDG), or Trusted Wireless Access Gateway (TWAG
<xref target="SDO-3GPP.23.402" />) .
</t>
<t>
3GPP specifications also include client-based mobility support, based on
adopting the use of Dual-Stack Mobile IPv6 (DSMIPv6) <xref target="RFC5555" />
for the S2c interface <xref target="SDO-3GPP.24.303" />. In this case, the User
Equipment (UE) implements the binding update functionality, while the home agent
role is played by the PGW.
</t>
<t>
A Local IP Access (LIPA) and Selected IP Traffic Offload (SIPTO) enabled network
<xref target="SDO-3GPP.23.401" /> allows offloading some IP services at the
local access network, above the Radio Access Network (RAN) or at the macro,
without the need to travel back to the PGW (see <xref target="fig:lipa" />).
</t>
<figure anchor="fig:lipa" title="LIPA scenario">
<artwork><![CDATA[
+---------+ IP traffic to mobile operator's CN
| User |····································(Operator's CN)
| Equipm. |··················
+---------+ . Local IP traffic
.
+-----------+
|Residential|
|enterprise |
|IP network |
+-----------+
]]></artwork>
</figure>
<t>
SIPTO enables an operator to offload certain types of traffic at a network node
close to the UE's point of attachment to the access network, by selecting a set
of GWs (SGW and PGW) that are geographically/topologically close to the UE's
point of attachment.
</t>
<figure anchor="fig:sipto" title="SIPTO architecture">
<artwork><![CDATA[
SIPTO Traffic
|
.
.
+------+ +------+
|L-PGW | ---- | MME |
+------+ / +------+
| /
+-------+ +------+ +------+/ +------+
| UE |·····|eNB |····| S-GW |········| P-GW |···> CN Traffic
+-------+ +------+ +------+ +------+
]]></artwork>
</figure>
<t>
LIPA, on the other hand, enables an IP addressable UE connected via a Home eNB
(HeNB) to access other IP addressable entities in the same
residential/enterprise IP network without traversing the mobile operator's
network core in the user plane. In order to achieve this, a Local GW (L-GW)
collocated with the HeNB is used. LIPA is established by the UE requesting a new
PDN (Public Data Network) connection to an access point name for which LIPA is
permitted, and the network selecting the Local GW associated with the HeNB and
enabling a direct user plane path between the Local GW and the HeNB.
</t>
<figure anchor="fig:lipa_arch" title="LIPA architecture">
<artwork><![CDATA[
+---------------+-------+ +----------+ +-------------+ =====
|Residential | |H(e)NB | | Backhaul | |Mobile | ( IP )
|Enterprise |..|-------|..| |..|Operator |..(Network)
|Network | |L-GW | | | |Core network | =======
+---------------+-------+ +----------+ +-------------+
/
|
/
+-----+
| UE |
+-----+
]]></artwork>
</figure>
<t>
The 3GPP architecture specifications also provide mechanisms to allow discovery
and selection of gateways <xref target="SDO-3GPP.29.303" />. These mechanisms
enable decisions taking into consideration topological location and
gateway collocation aspects, relying upon the DNS as a "location database".
</t>
<t>
Both SIPTO and LIPA have a very limited mobility support, specially in 3GPP
specifications up to Rel-12. Briefly, LIPA mobility support is limited to
handovers between HeNBs that are managed by the same L-GW (i.e., mobility within
the local domain). There is no guarantee of IP session continuity for SIPTO.
</t>
</section>
<!-- END 4.3. Flattening 3GPP mobile network approaches -->
</section>
<!-- END 4. DMM practices -->
<!-- BEGIN 5: Gap analysis -->
<section anchor="sec:gap" title="Gap analysis">
<t>
The goal of this section is to identify the limitations in the current
practices, described in <xref target="sec:practices" />, with respect to the
DMM requirements listed in <xref target="RFC7333" />.
</t>
<!-- BEGIN 5.1: Distributed mobility management - REQ1 -->
<section anchor="sec:req1" title="Distributed mobility management - REQ1">
<t>
According to requirement #1 stated in
<xref target="RFC7333" />, IP mobility, network access and
forwarding solutions provided by DMM must enable traffic to avoid traversing
single mobility anchor far from the optimal route.
</t>
<t>
From the analysis performed in <xref target="sec:practices"/>, a DMM deployment
can meet the requirement "REQ#1 Distributed mobility management" usually relying
on the following functions:
<list style="symbols">
<t>
Multiple (distributed) anchoring: ability to anchor different sessions of a
single mobile node at different anchors. In order to provide improved routing,
some anchors might need to be placed closer to the mobile node or the
corresponding node.
</t>
<t>
Dynamic anchor assignment/re-location: ability to i) assign the initial anchor,
and ii) dynamically change the initially assigned anchor and/or assign a new one
(this may also require to transfer mobility context between anchors). This can
be achieved either by changing anchor for all ongoing sessions or by assigning
new anchors just for new sessions.
</t>
</list>
</t>
<t>
Both the main client- and network-based IP mobility protocols, namely (DS)MIPv6
and PMIPv6 allow deploying multiple anchors (i.e., home agents and localized
mobility anchors), therefore providing the multiple anchoring function. However,
existing solutions only provide a initial anchor assignment, thus
the lack of dynamic anchor change/new anchor assignment is a gap. Neither the HA
switch nor the LMA runtime assignment allow changing the anchor during an
ongoing session. This actually comprises several gaps: ability to perform anchor
assignment at any time (not only at the initial MN's attachment), ability of the
current anchor to initiate/trigger the relocation, and ability to transfer
registration context between anchors.
</t>
<t>
Dynamic anchor assignment may lead the MN to manage different mobility sessions
served by different mobility anchors. This is not an issue with client based
mobility management where the mobility client natively knows each anchor
associated to each mobility sessions. However, there is one gap, as the MN
should be capable of handling IP addresses in a DMM-friendly way, meaning that
the MN can perform smart source address selection (i.e., deprecating IP
addresses from previous mobility anchors, so they are not used for new
sessions). Besides, managing different mobility sessions served by different
mobility anchors may raise issues with network based mobility management. In
this case, the mobile client, located in the network (e.g., MAG), usually
retrieves the MN's anchor from the MN's policy profile (e.g., Section 6.2 of
<xref target="RFC5213" />). Currently, the MN's policy profile implicitly
assumes a single serving anchor and, thus, does not maintain the association
between home network prefix and anchor.
</t>
<t>
The consequence of the distribution of the mobility anchors is that there might
be more than one available anchor for a mobile node to use, which leads to an
anchor discovery and selection issue. Currently, there is no efficient mechanism
specified to allow dynamically discovering the presence of nodes that can play
the anchor role, discovering their capabilities and selecting the most suitable
one. There is also no mechanism to allow selecting a node that is currently
anchoring a given home address/prefix (capability sometimes required to meet
REQ#2). There are though some mechanisms that could help discovering anchors,
such as the Dynamic Home Agent Address Discovery (DHAAD), the use of the Home
Agent (H) flag in Router Advertisements (which indicates that the router sending
the Router Advertisement is also functioning as a Mobile IPv6 home agent on the
link) or the MAP option in Router Advertisements defined by HMIPv6. Note that
there are 3GPP mechanisms providing that functionality defined in
<xref target="SDO-3GPP.29.303" />.
</t>
<t>
Regarding the ability to transfer registration context between anchors, there
are already some solutions that could be reused or adapted to fill that gap,
such as Fast Handovers for Mobile IPv6 <xref target="RFC5568" /> -- to enable
traffic redirection from the old to the new anchor --, the Context Transfer
protocol <xref target="RFC4067" /> -- to enable the required transfer of
registration information between anchors --, or the Handover Keying architecture
solutions <xref target="RFC6697" />, to speed up the re-authentication process
after a change of anchor. Note that some extensions might be needed in the
context of DMM, as these protocols were designed in the context of centralized
client IP mobility, focusing on the access re-attachment and authentication.
</t>
<t>
Also note that REQ1 is such that the data plane traffic can avoid suboptimal
route. Distributed processing of the traffic is then needed only in the data
plane. The needed capability in distributed processing therefore should not
contradict with centralized control plane. Other control plane solutions such as
charging, lawful interception, etc. should not be limited. Yet combining the
control plane and data plane forwarding management (FM) function may limit the
choice to distributing both data plane and control plane together. In order to
enable distributing only the data plane without distributing the control plane,
a gap is to split the forwarding management function into the control plane
(FM-CP) and data plane (FM-DP).
</t>
</section>
<!-- END 5.1: Distributed processing - REQ1 -->
<!-- BEGIN 5.2: Bypassable network-layer mobility support
for each application session - REQ2 -->
<section anchor="sec:req2"
title="Bypassable network-layer mobility support
for each application session - REQ2">
<t>
The need for "bypassable network-layer mobility support for each application
session" introduced in <xref target="RFC7333" /> requires
flexibility on determining whether network-layer mobility support is needed.
The requirement enables one to choose whether or not use network-layer mobility
support. It only enables the two following functions:
<list style="symbols">
<t>
Dynamically assign/relocate anchor: a mobility anchor is assigned only to
sessions which uses the network-layer mobility support. The MN may thus manage
more than one session; some of them may be associated with anchored IP
address(es), while the others may be associated with local IP address(es).
</t>
<t>
Multiple IP address management: this function is related to the preceding and is
about the ability of the mobile node to simultaneously use multiple IP addresses
and select the best one (from an anchoring point of view) to use on a
per-session/application/service basis. This requires MN to acquire information
regarding the properties of the available IP addresses.
</t>
</list>
</t>
<t>
The dynamic anchor assignment/relocation needs to ensure that IP address
continuity is guaranteed for sessions that uses such mobility support (e.g., in
some scenarios, the provision of mobility locally within a limited area might be
enough from the mobile node or the application point of view) at the relocated
anchor. Implicitly, when no applications are using the network-layer mobility
support, DMM may release the needed resources. This may imply having the
knowledge of which sessions at the mobile node are active and are using the
mobility support. This is something typically known only by the MN (e.g., by its
connection manager), and would also typically require some signaling support
(e.g., socket API extensions) from applications to indicate the IP stack whether
mobility support is required or not in. Therefore, (part of) this knowledge
might need to be transferred to/shared with the network.
</t>
<t>
Multiple IP address management provides the MN with the choice to pick-up the
correct address (provided with mobility support or not) depending on the
application requirements. When using client based mobility management, the
mobile node is itself aware of the anchoring capabilities of its assigned IP
addresses. This is not necessarily the case with network based IP mobility
management; current mechanisms do not allow the MN to be aware of the properties
of its IP addresses (e.g., the MN does not know whether the allocated IP
addresses are anchored). However, there are proposals that the network could
indicate such IP address properties during assignment procedures, such as
<xref target="I-D.bhandari-dhc-class-based-prefix"/>,
<xref target="I-D.korhonen-6man-prefix-properties"/> and
<xref target="I-D.anipko-mif-mpvd-arch" />. Although there exist these
individual efforts that could be be considered as attempts to fix the gap, there
is no solution adopted as a work item within any IETF working group.
</t>
<t>
The handling of mobility management to the granularity of an individual session
of a user/device needs proper session identification in addition to user/device
identification.
</t>
</section>
<!-- END 5.2: Bypassable network-layer mobility support - REQ2 -->
<!-- BEGIN 5.3: IPv6 deployment - REQ3 -->
<section anchor="sec:req3" title="IPv6 deployment - REQ3">
<t>
This requirement states that DMM solutions should primarily target IPv6 as the
primary deployment environment. IPv4 support is not considered mandatory and
solutions should not be tailored specifically to support IPv4.
</t>
<t>
All analyzed DMM practices support IPv6. Some of them, such as MIPv6/NEMO
(including the support of dynamic HA selection), MOBIKE, SIPTO have also IPv4
support. There are also some solutions that have some limited IPv4 support
(e.g., PMIPv6). In conclusion, this requirement is met by existing DMM
practices.
</t>
</section>
<!-- END 5.3: IPv6 deployment - REQ3 -->
<!-- BEGIN 5.4: Existing mobility protocols - REQ4 -->
<section anchor="sec:req4" title="Existing mobility protocols - REQ4">
<t>
A DMM solution must first consider reusing and extending IETF-standardized
protocols before specifying new protocols.
</t>
<t>
As stated in <xref target="RFC7333" />, a DMM solution could
reuse existing IETF and standardized protocols before specifying new protocols.
Besides, <xref target="sec:practices" /> of this document discusses various ways
to flatten and distribute current mobility solutions. Actually, nothing prevent
the distribution of mobility functions with in IP mobility protocols.
However, as discussed in <xref target="sec:req1" /> and
<xref target="sec:req2" />, limitations exist.
</t>
<t>
The 3GPP data plane anchoring function, i.e., the PGW, can be also be
distributed, but with limitations; e.g., no anchoring relocation, no context
transfer between anchors and centralized control plane. The 3GPP architecture is
also going into the direction of flattening with SIPTO and LIPA, though they do
not provide full mobility support. For example, mobility support for SIPTO
traffic can be rather limited, and offloaded traffic cannot access operator
services. Thus, the operator must be very careful in selecting which traffic to
offload.
</t>
</section>
<!-- END 5.4: Existing mobility protocols - REQ4 -->
<!-- BEGIN 5.5: Co-existence - REQ5 -->
<section anchor="sec:req5"
title="Coexistence with deployed networks/hosts
and operability across different networks- REQ5">
<t>
According to <xref target="RFC7333" />, DMM implementations
are required to co-exist with existing network deployments, end hosts and
routers. Additionally, DMM solutions are expected to work across different
networks, possibly operated as separate administrative domains, when the needed
mobility management signaling, forwarding, and network access are allowed by the
trust relationship between them. All current mobility protocols can co-exist
with existing network deployments and end hosts. There is no gap between
existing mobility protocols and this requirement.
</t>
</section>
<!-- END 5.5: Co-existence - REQ5 -->
<!-- BEGIN 5.6: Operation and management considerations - REQ6 -->
<section anchor="sec:req6" title="Operation and management considerations - REQ6">
<t>
This requirement actually comprises several aspects, as summarized below.
<list style="symbols">
<t>
A DMM solution needs to consider configuring a device, monitoring the current
operational state of a device, responding to events that impact the device,
possibly by modifying the configuration and storing the data in a format that
can be analyzed later.
</t>
<t>
A DMM solution has to describe in what environment and how it can be scalably
deployed and managed.
</t>
<t>
A DMM solution has to support mechanisms to test if the DMM solution is
working properly.
</t>
<t>
A DMM solution is expected to expose the operational state of DMM to the
administrators of the DMM entities.
</t>
<t>
A DMM solution, which supports flow mobility, is also expected to support means
to correlate the flow routing policies and the observed forwarding actions.
</t>
<t>
A DMM solution is expected to support mechanisms to check the liveness of
forwarding path.
</t>
<t>
A DMM solution has to provide fault management and monitoring mechanisms to
manage situations where update of the mobility session or the data path fails.
</t>
<t>
A DMM solution is expected to be able to monitor the usage of the DMM protocol.
</t>
<t>
DMM solutions have to support standardized configuration with NETCONF
<xref target="RFC6241"/>, using YANG <xref target="RFC6020"/> modules, which
are expected to be created for DMM when needed for such configuration.
</t>
</list>
</t>
<t>
Existing mobility management protocols have not thoroughly documented the above
list of operation and management considerations. Each of the above needs to be
considered from the beginning in a DMM solution.
</t>
<t>
Management information base (MIB) objects are currently defined in
<xref target="RFC4295"/> for MIPv6 and in <xref target="RFC6475"/> for PMIPv6.
Standardized configuration with NETCONF <xref target="RFC6241"/>, using YANG
<xref target="RFC6020"/> modules is needed.
</t>
</section>
<!-- END 5.6: Operation and management considerations - REQ6 -->
<!-- BEGIN 5.7: Security considerations - REQ7 -->
<section anchor="sec:req7" title="Security considerations - REQ7">
<t>
As stated in <xref target="RFC7333" />, a DMM solution has to
support any security protocols and mechanisms needed to secure the network and
to make continuous security improvements. In addition, with security taken into
consideration early in the design, a DMM solution cannot introduce new security
risks, or amplify existing security risks, that cannot be mitigated by existing
security protocols and mechanisms.
</t>
<t>
Current mobility protocols have all security mechanisms in place. For example,
Mobile IPv6 defines security features to protect binding updates both to home
agents and correspondent nodes. It also defines mechanisms to protect the data
packets transmission for Mobile IPv6 users. Proxy Mobile IPv6 and other
variations of mobile IP also have similar security considerations.
</t>
</section>
<!-- END 5.7: Security considerations - REQ7 -->
<!-- BEGIN 5.8: Multicast - REQ8 -->
<section anchor="sec:req8" title="Multicast - REQ8">
<t>
It is stated in <xref target="RFC7333" /> that DMM solutions
are expected to enable multicast solutions to be developed to avoid network
inefficiency in multicast traffic delivery.
</t>
<t>
Current IP mobility solutions address mainly the mobility problem for unicast
traffic. Solutions relying on the use of an anchor point for tunneling multicast
traffic down to the access router, or to the mobile node, introduce the
so-called “tunnel convergence problem”. This means that multiple instances of
the same multicast traffic can converge to the same node, diminishing the
advantage of using multicast protocols.
</t>
<t>
<xref target="RFC6224"/> documents a baseline solution for the previous issue,
and <xref target="RFC7028"/> a routing optimization solution. The baseline
solution suggests deploying an MLD proxy function at the MAG, and either a
multicast router or another MLD proxy function at the LMA. The routing
optimization solution describes an architecture where a dedicated multicast tree
mobility anchor (MTMA) or a direct routing option can be used to avoid the
tunnel convergence problem.
</t>
<t>
Besides the solutions highlighted before, there are no other mechanisms for
mobility protocols to address the multicast tunnel convergence problem.
</t>
</section>
<!-- END 5.8: Multicast - REQ8 -->
<!-- BEGIN 5.9: Summary -->
<section anchor="sec:req_summary" title="Summary">
<t>
We next list the main gaps identified from the analysis performed above:
<list style="symbols">
<t>
Existing solutions only provide an optimal initial anchor assignment, a gap
being the lack of dynamic anchor change/new anchor assignment. Neither the HA
switch nor the LMA runtime assignment allow changing the anchor during an
ongoing session. MOBIKE allows change of GW but its applicability has been
scoped to very narrow use case.
</t>
<t>
The mobile node needs to simultaneously use multiple IP addresses with different
properties, which requires to expose this information to the mobile node and to
update accordingly the source address selection mechanism of the latter.
</t>
<t>
Currently, there is no efficient mechanism specified by the IETF that allows to
dynamically discover the presence of nodes that can play the role of anchor,
discover their capabilities and allow the selection of the most suitable one.
However, the following mechanisms that could help discovering anchors:
</t>
<t>
Dynamic Home Agent Address Discovery (DHAAD):
the use of the Home Agent (H) flag
in Router Advertisements (which indicates that the router sending the Router
Advertisement is also functioning as a Mobile IPv6 home agent on the link) and
the MAP option in Router Advertisements defined by HMIPv6.
</t>
<t>
While existing network-based DMM practices may allow to deploy multiple LMAs
and dynamically select the best one, this requires to still keep some
centralization in the control plane, to access the policy database (as defined
in RFC5213). Although <xref target="I-D.ietf-netext-pmip-cp-up-separation"/>
allows a MAG to perform splitting of its control and user planes, there is a
lack of solutions/extensions that support a clear control and data plane
separation for IETF IP mobility protocols in a DMM context.
</t>
</list>
</t>
</section>
<!-- END 5.9: Summary -->
</section>
<!-- END 5. Gap analysis -->
<!-- BEGIN 6. Security Considerations -->
<section anchor="sec:security" title="Security Considerations">
<t>
Distributed mobility management systems encounter same security threats as
existing centralized IP mobility protocols. Without authentication, a malicious
node could forge signaling messages and redirect traffic from its legitimate
path. This would amount to a denial of service attack against the specific node
or nodes for which the traffic is intended. Distributed mobility anchoring,
while keeping current security mechanisms, might require more security
associations to be managed by the mobility management entities, potentially
leading to scalability and performance issues. Moreover, distributed mobility
anchoring makes mobility security problems more complex, since traffic
redirection requests might come from previously unconsidered origins, thus
leading to distributed points of attack. Consequently, the DMM security design
needs to account for the distribution of security associations between
additional mobility entities.
</t>
</section>
<!-- END 6. Security Considerations -->
<!-- BEGIN 7. IANA Considerations -->
<section anchor="sec:iana" title="IANA Considerations">
<t>
None.
</t>
</section>
<!-- END 7. IANA Considerations -->
<section title="Contributors">
<t>This document has benefited
to valuable contributions from
<figure><artwork><![CDATA[
Charles E. Perkins
Huawei Technologies
EMail: charliep@computer.org
]]></artwork></figure>
who had produced a matrix to compare the different mobility protocols and extensions
against a list of desired DMM properties.
They were useful inputs in the early work of gap analysis.
He had continued to give suggestions
as well as extensive review comments to this documents.
</t>
</section>
</middle>
<back>
<references title="Normative References">
<!-- &RFC2119; -->
&RFC7333;
</references>
<references title="Informative References">
&RFC4295;
&RFC6020;
&RFC6241;
&RFC6475;
&RFC6275;
&RFC5213;
&RFC5555;
&RFC5844;
&RFC3963;
&RFC4640;
&RFC5026;
&RFC6611;
&RFC4225;
&RFC5380;
&RFC5142;
&RFC6705;
&RFC6463;
&RFC4555;
&RFC5996;
&RFC5014;
&RFC6224;
&RFC7028;
&RFC4889;
&RFC4066;
&RFC4067;
&RFC5568;
&RFC6697;
&RFC6097;
&RFC4960;
&RFC6724;
&I-D.gundavelli-v6ops-community-wifi-svcs;
&I-D.bhandari-dhc-class-based-prefix;
&I-D.korhonen-6man-prefix-properties;
&I-D.anipko-mif-mpvd-arch;
&I-D.ietf-netext-pmip-cp-up-separation;
&TS29060;
&TR29281;
&TS29274;
&TS23401;
&TS23402;
&TS29303;
<reference anchor="IEEE.802-16.2009"
target="http://standards.ieee.org/getieee802/download/802.16-2009.pdf">
<front>
<title>
IEEE Standard for Local and metropolitan area networks Part 16: Air Interface
for Broadband Wireless Access Systems
</title>
<author>
<organization/>
</author>
<date month="" year="2009"/>
</front>
<seriesInfo name="IEEE" value="Standard 802.16"/>
</reference>
<reference anchor="SDO-3GPP.24.303">
<front>
<title>
Mobility management based on Dual-Stack Mobile IPv6; Stage 3
</title>
<author>
<organization>3GPP</organization>
</author>
<date day="27" month="June" year="2013"/>
</front>
<seriesInfo name="3GPP TS" value="24.303 10.0.0"/>
<format type="HTML" target="http://www.3gpp.org/ftp/Specs/html-info/24303.htm"/>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 05:26:53 |