One document matched: draft-ietf-dmm-requirements-09.xml


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docName="draft-ietf-dmm-requirements-09">

<front>
<title abbrev="DMM-Reqs">
Requirements for Distributed Mobility Management
</title>

<author initials="H" surname="Chan (Ed.)" 
fullname="H Anthony Chan (editor)">
<organization>Huawei Technologies (more co-authors on P. 17)</organization>
<address>
<postal>
<street>5340 Legacy Dr. Building 3, Plano, TX 75024, USA</street>
<street>Email: h.a.chan@ieee.org</street>
</postal>
</address>
</author>

<author initials="D" surname="Liu" 
fullname="Dapeng Liu">
<organization>China Mobile</organization>
<address>
<postal>
<street>Unit2, 28 Xuanwumenxi Ave, Xuanwu District,
Beijing 100053, China</street>
<street>Email: liudapeng@chinamobile.com</street>
</postal>
</address>
</author>

<author initials="P" surname="Seite" 
fullname="Pierrick Seite">
<organization>Orange</organization>
<address>
<postal>
<street>4, rue du Clos Courtel, BP 91226,
Cesson-Sevigne 35512, France</street>
<street>Email: pierrick.seite@orange.com</street>
</postal>
</address>
</author>

<author initials="H" surname="Yokota" 
fullname="Hidetoshi Yokota">
<organization>KDDI Lab</organization>
<address>
<postal>
<street>2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan</street>
<street>Email: yokota@kddilabs.jp</street>
</postal>
</address>
</author>

<author initials="J" surname="Korhonen" 
fullname="Jouni Korhonen">
<organization>Renesas Mobile</organization>
<address>
<postal>
<street>Porkkalankatu 24, FIN-00180 Helsinki, Finland</street>
<street>Email: jouni.korhonen@nsn.com</street>
<street>-</street>
<street>Charles E. Perkins</street>
<street>Huawei Technologies</street>
<street>Email: charliep@computer.org</street>
<street>-</street>
<street>Melia Telemaco</street>
<street>Alcatel-Lucent Bell Labs</street>
<street>Email: telemaco.melia@alcatel-lucent.com</street>
<street>-</street>
<street>Elena Demaria</street>
<street>Telecom Italia</street>
<street>via G. Reiss Romoli, 274, TORINO, 10148, Italy</street>
<street>Email: elena.demaria@telecomitalia.it</street>
<street>-</street>
<street>Jong-Hyouk Lee</street>
<street>Sangmyung University</street>
<street>Email: hurryon@gmail.com</street>
<street>-</street>
<street>Kostas Pentikousis</street>
<street>Huawei Technologies</street>
<street>Carnotstr. 4 10587 Berlin, Germany</street>
<street>Email: k.pentikousis@huawei.com</street>
<street>-</street>
<street>Tricci So</street>
<street>ZTE</street>
<street>Email: tso@zteusa.com</street>
<street>-</street>
<street>Carlos J. Bernardos</street>
<street>Universidad Carlos III de Madrid</street>
<street>Av. Universidad, 30, Leganes, Madrid 28911, Spain</street>
<street>Email: cjbc@it.uc3m.es</street>
<street>-</street>
<street>Peter McCann</street>
<street>Huawei Technologies</street>
<street>Email: PeterMcCann@huawei.com</street>
<street>-</street>
<street>Seok Joo Koh</street>
<street>Kyungpook National University, Korea</street>
<street>Email: sjkoh@knu.ac.kr</street>
<street>-</street>
<street>Wen Luo</street>
<street>ZTE</street>
<street>No.68, Zijinhua RD,Yuhuatai District, Nanjing, Jiangsu 210012, China</street>
<street>Email: luo.wen@zte.com.cn</street>
<street>-</street>
<street>Sri Gundavelli</street>
<street>Cisco</street>
<street>sgundave@cisco.com</street>
<street>-</street>
<street>Marco Liebsch</street>
<street>NEC Laboratories Europe</street>
<street>Email: liebsch@neclab.eu</street>
<street>-</street>
<street>Carl Williams</street>
<street>MCSR Labs</street>
<street>Email: carlw@mcsr-labs.org</street>
<street>-</street>
<street>Seil Jeon</street>
<street>Instituto de Telecomunicacoes, Aveiro</street>
<street>Email: seiljeon@av.it.pt</street>
<street>-</street>
<street>Sérgio Figueiredo</street>
<street>Universidade de Aveiro</street>
<street>Email: sfigueiredo@av.it.pt</street>
<street>-</street>
<street>Stig Venaas</street>
<street>Email: stig@venaas.com</street>
<street>-</street>
<street>Luis Miguel Contreras Murillo</street>
<street>Telefonica I+D</street>
<street>Email: lmcm@tid.es</street>
<street>-</street>
<street>Juan Carlos Zuniga</street>
<street>InterDigital</street>
<street>Email: JuanCarlos.Zuniga@InterDigital.com</street>
<street>-</street>
<street>Alexandru Petrescu</street>
<street>Email: alexandru.petrescu@gmail.com</street>
<street>-</street>
<street>Georgios Karagiannis</street>
<street>University of Twente</street>
<street>Email: g.karagiannis@utwente.nl</street>
<street>-</street>
<street>Julien Laganier</street>
<street>Juniper</street>
<street>jlaganier@juniper.net</street>
<street>-</street>
<street>Wassim Michel Haddad</street>
<street>Ericsson</street>
<street>Wassam.Haddad@ericsson.com</street>
<street>-</street>
<street>Dirk von Hugo</street>
<street>Deutsche Telekom Laboratories</street>
<street>Dirk.von-Hugo@telekom.de</street>
<street>-</street>
<street>Ahmad Muhanna</street>
<street>Award Solutions</street>
<street>amuhanna@awardsolutions.com</street>
<street>-</street>
<street>Byoung-Jo Kim</street>
<street>ATT Labs</street>
<street>macsbug@research.att.com</street>
<street>-</street>
<street>Hassan Ali-Ahmad</street>
<street>Orange</street>
<street>hassan.aliahmad@orange.com</street>
<street>-</street>

</postal>
</address>
</author>

<date month="September" year="2013"></date>
<area></area>
<workgroup></workgroup>

<abstract>
<t>
This document defines the requirements 
for Distributed Mobility Management (DMM).
The hierarchical structure 
in traditional wireless networks 
has led primarily to centralized deployment models. 
As some wireless networks are evolving away from the hierarchical structure,
such as in moving the content delivery servers closer to the users,
a distributed model for mobility management 
can be useful to them. 
</t>
</abstract>

<note title="Requirements Language">
<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 RFC 2119 <xref target="RFC2119">RFC 2119</xref>.
</t>
</note>

</front>

<middle>

<section anchor="intro" title="Introduction">

<t>
In the past decade a fair number of mobility protocols 
have been standardized
 <xref target="RFC6275"/>
 <xref target="RFC5944"/>
 <xref target="RFC5380"/>
 <xref target="RFC6301"/>
 <xref target="RFC5213"/>.
Although the protocols differ 
in terms of functions and associated message formats, 
they all employ a mobility anchor
to allow a mobile node to remain reachable 
after it has moved to a different network. 
The anchor point, among other tasks, 
ensures connectivity 
by forwarding packets 
destined to, or sent from, the mobile node. 
It is a centrally deployed mobility anchor
in the sense that the deployed architectures today 
have a small number of these anchors 
and the traffic of millions of mobile nodes 
in an operator network are typically managed 
by the same anchor.
</t>

<t>
Distributed mobility management (DMM) is an alternative
to the above centralized deployment.
The background behind the interests to study DMM 
are primarily in the following. 
</t>

<t>
<list style='format (%d)'>

<t>
Mobile users are, more than ever, 
consuming Internet content; 
such traffic imposes new requirements 
on mobile core networks for data traffic delivery. 
The presence of content providers 
closer to 
Internet Service Providers (ISP) network 
requires taking into account 
local Content Delivery Networks (CDNs) 
while providing mobility services.
Moreover, when the traffic demand exceeds available capacity, 
service providers need to implement new strategies 
such as selective IPv4 traffic offload 
(e.g. 
 <xref target="RFC6909"/>,
3GPP work items LIPA/SIPTO 
[TS.23.401])
through alternative access networks (e.g. WLAN)
[Paper-Mobile.Data.Offloading]. 
A gateway selection mechanism
also takes the user proximity into account
within EPC [TS.29303]. 
These mechanisms were not pursued in the past
owing to charging and billing reasons.
Assigning a gateway anchor node
from a visited network in roaming scenario
has until recently been done and are limited
to voice services only. 
Charging and billing
require solutions beyond the mobility protocol.

<vspace blankLines="1" />

Both traffic offloading and CDN mechanisms 
could benefit from the development of mobile architectures 
with fewer levels of routing hierarchy 
introduced into the data path 
by the mobility management system. 
This trend towards so-called "flat networks" 
works best for direct communications among peers 
in the same geographical area. 
Distributed mobility management 
in a truly flat mobile architecture
would anchor the traffic 
closer to the point of attachment of the user.
</t>

<t>
Today's mobile networks present 
service providers with new challenges. 
Mobility patterns indicate that 
mobile nodes often
remain attached to the same point of attachment
for considerable periods of time
[Paper-Locating.User].
Specific IP mobility management support 
is not required for applications 
that launch and complete their sessions 
while the mobile node is connected 
to the same point of attachment. 
However, currently,
IP mobility support is designed for always-on operation,
maintaining all parameters of the context 
for each mobile subscriber 
for as long as they are connected to the network. 
This can result in a waste of resources 
and unnecessary costs for the service provider. 
Infrequent node mobility 
coupled with application intelligence
suggest that mobility support could be provided selectively
such as in [I-D.bhandari-dhc-class-based-prefix]
and [I-D.korhonen-6man-prefix-properties], 
thus reducing the amount of context maintained 
in the network.
</t>

</list>
</t>

<t>
In addition, considerations in the study of DMM are in the following.
</t>

<t>
<list style='format (%d)'>

<t>
To optimize handovers from the perspective of mobile nodes, 
the base protocols have been extended 
to efficiently handle packet forwarding 
between the previous and new points of attachment. 
These extensions are necessary 
when applications have stringent requirements 
in terms of delay. 
Notions of localization and distribution of local agents 
have been introduced to reduce signaling overhead
at the centralized routing anchor point
[Paper-Distributed.Centralized.Mobility]. 
Unfortunately, such protocols have not been deployed today. 
</t>

<t>
Most existing mobility protocols
have not been designed for multiple-interface hosts
which are capable to use multiple interfaces simultaneously.
Retrofitting the required functionality
can result in an unnecessary increase in the protocol complexity. 
</t>

<t>
IP multicast support, 
including optimizations, have been introduced 
as an effective transport method 
for multimedia data delivery,
but by "patching-up" procedure 
after completing the design of 
reference mobility protocol, 
leading to network inefficiency and non-optimal routing.
</t>

</list>
</t>

<t>
The distributed mobility management (DMM) charter 
addresses two complementary aspects 
of mobility management procedures: 
the distribution of mobility anchors 
in the data-plane
towards a more flat network 
and the selective activation/deactivation 
of mobility protocol support 
as an enabler to distributed mobility management. 
The former aims at positioning mobility anchors 
(e.g., HA, LMA) 
closer to the user; 
ideally, 
mobility agents could be collocated 
with the first-hop router.
The latter, 
facilitated by the distribution of mobility anchors, 
identifies when mobility support must be activated 
and when sessions 
do not require mobility management support
-- thus reducing the amount of state information 
that must be maintained 
in various mobility agents of the mobile network. 
It can then avoid the unnecessary establishment of mechanisms
to forward traffic from an old to a new mobility anchor.
</t>

<t>
This document compares distributed mobility management 
with centralized mobility management in Section 3. 
The problems that can be addressed with DMM 
are summarized in Section 4. 
The mandatory requirements as well as the optional requirements 
are given in Section 5. 
Finally, security considerations are discussed in Section 6.
</t>
<t>
The problem statement and the use cases
[I-D.yokota-dmm-scenario]
can be found in 
[Paper-Distributed.Mobility.Review].
</t>

</section>

<section title="Conventions used in this document">

<section title="Terminology">
<t>All the 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 Mobility Related Terminology 
 <xref target="RFC3753"/>. 
These terms include the following:
mobile node (MN), correspondent node (CN), 
and home agent (HA) as per 
 <xref target="RFC6275"/>; 
local mobility anchor (LMA) 
and mobile access gateway (MAG) as per 
 <xref target="RFC5213"/>,
and context as per
 <xref target="RFC3753"/>.
</t>

<t>
In addition, this draft introduces the following terms. 
</t>

<t>
<list style='hanging'>

<t hangText='Centrally deployed mobility anchors'>
<vspace blankLines="1" />
refer to the mobility management deployments
in which there are very few mobility anchors
and the traffic of millions of mobile nodes
in an operator network
are managed by the same anchor.
</t>

<t hangText='Centralized mobility management'>
<vspace blankLines="1" />
makes use of centrally deployed mobility anchors.
</t>

<t hangText='Distributed mobility management'>
<vspace blankLines="1" />
is not centralized so that
traffic does not need to traverse 
centrally deployed mobility anchors.
</t>

<t hangText='Flat mobile network'>
<vspace blankLines="1" />
has few levels of routing hierarchy
introduced into the data path
by the mobility management system.
</t>

<t hangText='Mobility context'>
<vspace blankLines="1" />
is the collection of information 
required to provide mobility management support 
for a given mobile node.
</t>

</list>
</t>

</section>

</section>


<section 
title="Centralized versus distributed mobility management">
<t>
Mobility management functions 
may be implemented at different layers 
of the protocol stack. 
At the IP (network) layer, 
mobility management can be client-based or network-based. 
</t>

<t>
An IP-layer mobility management protocol
is typically based on the principle 
of distinguishing between session identifier and routing address
and maintaining a mapping between the two. 
In Mobile IP, 
the home address serves as the session identifier 
whereas the care-of-address (CoA) 
takes the role of the routing address.
The binding between these two 
is maintained at the home agent (mobility anchor).
If packets addressed to the home address
of a mobile node can be continuously delivered to the node,
then all sessions using that home address 
are unaffected
even though the routing address (CoA) changes.
</t>

<t>
The next two subsections explain centralized and distributed
mobility management functions in the network.
</t>

<section title="Centralized mobility management">
<t>
In centralized mobility management, 
the mapping information 
between the session identifier 
and the locator IP address of a mobile node (MN) 
is kept at a single mobility anchor. 
At the same time,
packets destined to the MN are routed via this anchor. 
In other words, 
such mobility management systems are centralized 
in both the control plane and the data plane
(mobile node IP traffic).
</t>

<t>
Many existing mobility management deployments 
make use of centralized mobility anchoring 
in a hierarchical network architecture, 
as shown in Figure 1. 
Examples of such centralized mobility anchors 
are the home agent (HA) and local mobility anchor (LMA) 
in Mobile IPv6 
<xref target="RFC6275"/> 
and Proxy Mobile IPv6 
<xref target="RFC5213"/>, 
respectively. 
Current cellular networks 
such as the Third Generation Partnership Project (3GPP) 
GPRS networks, CDMA networks, 
and 3GPP Evolved Packet System (EPS) networks 
employ centralized mobility management too. 
In particular, 
the Gateway GPRS Support Node (GGSN), 
Serving GPRS Support Node (SGSN) 
and Radio Network Controller (RNC)
in the 3GPP GPRS hierarchical network, 
and the Packet Data Network Gateway (P-GW) 
and Serving Gateway (S-GW) in the 3GPP EPS network
all act as anchors in a hierarchy.
</t>

      <figure>
        <preamble></preamble>
        <artwork><![CDATA[
         3G GPRS                 3GPP EPS                MIP/PMIP
         +------+                +------+                +------+      
         | GGSN |                | P-GW |                |HA/LMA|      
         +------+                +------+                +------+      
            /\                      /\                      /\
           /  \                    /  \                    /  \
          /    \                  /    \                  /    \ 
         /      \                /      \                /      \
        /        \              /        \              /        \
       /          \            /          \            /          \
      /            \          /            \          /            \
  +------+      +------+  +------+      +------+  +------+      +------+
  | SGSN |      | SGSN |  | S-GW |      | S-GW |  |MN/MAG|      |MN/MAG|
  +------+      +------+  +------+      +------+  +------+      +------+
     /\            /\
    /  \          /  \
   /    \        /    \
+---+  +---+  +---+  +---+
|RNC|  |RNC|  |RNC|  |RNC|
+---+  +---+  +---+  +---+
      	]]></artwork>
        <postamble></postamble>
      </figure>

<t>Figure 1. Centralized mobility management.
</t>
</section>

<section title="Distributed mobility management">
<t>Mobility management functions may also be distributed 
to multiple networks
as shown in Figure 2, 
so that a mobile node in any of these networks
may be served by a nearby mobility function (MF). 
</t>

      <figure>
        <preamble></preamble>
        <artwork><![CDATA[
                 +------+  +------+  +------+  +------+    
                 |  MF  |  |  MF  |  |  MF  |  |  MF  |    
                 +------+  +------+  +------+  +------+    
                                        |          
                                      +----+          
                                      | MN |          
                                      +----+          
      	]]></artwork>
        <postamble></postamble>
      </figure>

<t>Figure 2. Distributed mobility management.
</t>
<t>
Mobility management may be partially or fully distributed
[I-D.yokota-dmm-scenario].
In the former case only the data plane is distributed,
implicitly assuming separation of data and control planes
as described in 
[I-D.wakikawa-netext-pmip-cp-up-separtion].
Fully distributed mobility management implies that
both the data plane and the control plane are distributed.
While mobility management can be distributed,
it is not necessary 
for other functions
such as subscription management, 
subscription database, and network access authentication to be similarly distributed.
</t>

<t>
A distributed mobility management scheme 
for a flat mobile network
of access nodes is proposed in 
[Paper-Distributed.Dynamic.Mobility]. 
Its benefits 
over centralized mobility management 
are shown through simulations in 
[Paper-Distributed.Centralized.Mobility].
Moreover,
the (re)use and extension of existing protocols 
in the design of both fully distributed mobility management
[Paper-Migrating.Home.Agents] 
[Paper-Distributed.Mobility.SAE]
and partially distributed mobility management
[Paper-Distributed.Mobility.PMIP]
[Paper-Distributed.Mobility.MIP]
have been reported in the literature. 
Therefore,
before designing new mobility management protocols 
for a future distributed architecture, 
it is recommended to first consider 
whether existing mobility management protocols 
can be extended. 

</t>

</section>

</section>


<section 
title="Problem Statement">
<t>
The problems that can be addressed with DMM are summarized in the following:
</t>

<t>
<list style='format PS%d:' counter="PS_count">

<!-- PS1 -->
<t>
Non-optimal routes
<vspace blankLines="1" />
Routing via a centralized anchor 
often results in non-optimal routes,
thereby increasing the end-to-end delay.
The problem is manifested, for example,
when accessing a nearby server or servers 
of a Content Delivery Network (CDN),
or when receiving locally available IP multicast 
or sending IP multicast packets.
(Existing route optimization 
is only a host-based solution. 
On the other hand, 
localized routing with PMIPv6 
 <xref target="RFC6705"/>
addresses only a part of the problem 
where both the MN and the CN 
are located in the PMIP domain 
and attached to a MAG, 
and is not applicable 
when the CN is outside the PMIP domain
or does not behave like an MN.)
</t>

<!-- PS2 -->
<t>
Divergence from other evolutionary trends in network architectures
such as distribution of content delivery.
<vspace blankLines="1" />
Centralized mobility management 
can become non-optimal 
with a flat network architecture.
</t>

<!-- PS3 -->
<t>
Low scalability of centralized tunnel management 
and mobility context maintenance
<vspace blankLines="1" />
Setting up tunnels through a central anchor
and maintaining mobility context 
for each MN 
usually requires more concentrated resources
in a centralized design,
thus reducing scalability. 
Distributing the tunnel maintenance function 
and the mobility context maintenance function 
among different network entities 
with proper signaling protocol design
can increase scalability.
</t>

<!-- PS4 -->
<t>
Single point of failure and attack
<vspace blankLines="1" />
Centralized anchoring designs 
may be more vulnerable 
to single points of failures and attacks
than a distributed system. 
The impact of a successful attack 
on a system with centralized mobility management 
can be far greater as well.
</t>

<!-- PS5 -->
<t>
Unnecessary mobility support 
to nodes that do not need it
<vspace blankLines="1" />
IP mobility support is not always required,
and not every parameter of mobility context is always used. 
For example, 
some applications do not need a stable IP address 
during a handover to maintain session continuity. 
Sometimes, the entire application session runs 
while the terminal does not change the point of attachment. 
Besides, some sessions, e.g. SIP-based sessions, 
can handle mobility at the application layer 
and hence do not need IP mobility support; 
it is then more efficient 
to deactivate IP mobility support for such sessions.
</t>

<!-- PS6 -->
<t>
(Related problem)
Mobility signaling overhead 
with peer-to-peer communication
<vspace blankLines="1" />
Wasting resources when mobility signaling 
(e.g., maintenance of the tunnel, keep alive signaling, etc.) 
is not turned off for peer-to-peer communication. 
Peer-to-peer communications 
have particular traffic patterns
that often do not benefit from mobility support
from the network.
Thus, the associated mobility support signaling
(e.g., maintenance of the tunnel, keep alive signaling, etc.) 
wastes network resources for no application gain.
</t>

<!-- PS7 -->
<t>
(Related problem)
Deployment with multiple mobility solutions
<vspace blankLines="1" />
There are already many variants and extensions of MIP. 
Deployment of new mobility management solutions can be challenging, 
and debugging difficult, 
when they must co-exist with solutions already in the field.
</t>

<!-- PS8 -->
<t>
Duplicate multicast traffic
<vspace blankLines="1" />
IP multicast distribution over architectures 
using IP mobility solutions 
(e.g., <xref target="RFC6224"/>) 
may lead to convergence 
of duplicated multicast subscriptions 
towards the downstream tunnel entity 
(e.g. MAG in PMIPv6).
Concretely, 
when multicast subscription 
for individual mobile nodes 
is coupled with mobility tunnels
(e.g. PMIPv6 tunnel), 
duplicate multicast subscription(s) 
is prone to be received 
through different upstream paths. 
This problem may also exist 
or be more severe 
in a distributed mobility environment. 
</t>
</list>
</t>

</section>


<section title="Requirements">
<t>
After comparing distributed mobility management
against centralized deployment in Section 3,
this section identifies 
the following requirements:
</t>

<!-- REQ1 -->
<section 
title="Distributed processing">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Distributed processing
<vspace blankLines="1" />
IP mobility, network access and routing solutions
provided by DMM 
MUST enable distributed processing 
for mobility management 
so that traffic 
does not need to traverse centrally deployed
mobility anchors and thereby avoid non-optimal routes.
<vspace blankLines="1" />
Motivation: 
This requirement is motivated by 
current trends in network evolution:
(a) it is cost- and resource-effective 
to cache and distribute content 
by combining distributed mobility anchors 
with caching systems 
(e.g., CDN); 
(b) the significantly larger number of mobile nodes
and flows
call for improved scalability; 
(c) single points of failure are avoided
in a distributed system; 
(d) threats against centrally deployed anchors,
e.g., home agent and local mobility anchor,
are mitigated in a distributed system. 
</t>
</list>
</t>

<t>
This requirement addresses the problems 
PS1, PS2, PS3, and PS4 described in Section 4.
</t>

</section>

<!-- REQ2 -->
<section 
title="Transparency to Upper Layers when needed">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Transparency to Upper Layers when needed
<vspace blankLines="1" />
DMM solutions MUST provide 
transparent mobility support above the IP layer 
when needed. 
Such transparency is needed,
for example, when, 
upon change of point of attachment to the network, 
an application flow cannot cope with a change 
in the IP address. 
However, it is not always necessary
to maintain a stable home IP address or prefix
for every application or at all times for a mobile node.
<vspace blankLines="1" />
Motivation:
The motivation of this requirement is to
enable more efficient routing 
and more efficient use of network resources 
by selecting an IP address or prefix
according to
whether mobility support is needed
and by not maintaining context 
at the mobility anchor 
when there is no such need.
</t>
</list>
</t>

<t>
This requirement addresses the problem 
PS5 as well as the related problem PS6 stated in Section 4.
</t>


</section>

<!-- REQ3 -->
<section 
title="IPv6 deployment">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
IPv6 deployment
<vspace blankLines="1" />
DMM solutions SHOULD target IPv6 
as the primary deployment environment
and SHOULD NOT be tailored specifically to support IPv4, 
in particular in situations 
where private IPv4 addresses and/or NATs are used.
<vspace blankLines="1" />
Motivation:
This requirement conforms
to the general orientation of IETF work. 
DMM deployment is foreseen 
in mid- to long-term horizon,
when IPv6 is expected 
to be far more common than today.
</t>
</list>
</t>

<t>
This requirement avoids the unnecessarily complexity 
in solving the problems in Section 4 for IPv4, 
which will not be able to use 
some of the IPv6-specific features.
</t>

</section>

<!-- REQ4 -->
<section 
title="Existing mobility protocols">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Existing mobility protocols
<vspace blankLines="1" />
A DMM solution SHOULD 
first consider reusing and extending 
IETF-standardized protocols 
before specifying new protocols.
<vspace blankLines="1" />
Motivation:
Reuse of existing IETF work
is more efficient and less error-prone.
</t>
</list>

</t>

<t>
This requirement attempts to avoid the need of
new protocols development
and therefore their potential problems 
of being time-consuming and error-prone.
</t>

</section>

<!-- REQ5 -->
<section 
title="Co-existence">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Co-existence with deployed networks and hosts
<vspace blankLines="1" />
The DMM solution MUST
be able to co-exist 
with existing network deployments and end hosts.
For example,
depending on the environment in which DMM is deployed,
DMM solutions
may need to be compatible 
with other deployed mobility protocols
or may need to co-exist
with a network or mobile hosts/routers
that do not support DMM protocols.
The mobile node may also move between different access networks,
where some of them may support neither DMM
nor another mobility protocol. 
Furthermore,
a DMM solution SHOULD work across different networks,
possibly operated as separate administrative domains, 
when allowed by the trust relationship
between them. 
<vspace blankLines="1" />
Motivation: 
(a) to preserve backwards compatibility 
so that existing networks and hosts 
are not affected 
and continue to function as usual,
and 
(b) enable inter-domain operation if desired.
</t>
</list>
</t>

<t>
This requirement addresses 
the related problem PS7 described in Section 4.
</t>


</section>

<!-- REQ6 -->
<section 
title="Security considerations">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Security considerations
<vspace blankLines="1" />
A DMM solution MUST not introduce new security risks 
or amplify existing security risks 
against which the existing security mechanisms/protocols
cannot offer sufficient protection. 
<vspace blankLines="1" />
Motivation:
Various attacks such as impersonation, denial of service, 
man-in-the-middle attacks, and so on, 
may be launched in a DMM deployment. 
For instance, 
an illegitimate node 
may attempt to access a network providing DMM. 
Another example is that 
a malicious node can forge a number of signaling messages 
thus redirecting traffic from its legitimate path.
Consequently, 
the specific node is under a denial of service attack, 
whereas other nodes do not receive their traffic. 
Accordingly, 
security mechanisms/protocols providing access control, 
integrity, authentication, authorization, 
confidentiality, etc. 
can be used to protect the DMM entities 
as they are already used to protect 
against existing networks 
and existing mobility protocols defined in IETF. 
In addition, 
end-to-end security measures between communicating nodes 
may already be used 
when deploying existing mobility protocols 
where the signaling messages travel over the Internet. 
For instance, 
EAP-based authentication 
can be used for network access security, 
while IPsec can be used for end-to-end security. 
When the existing security mechanisms/protocols 
are applied to protect the DMM entities, 
the security risks that may be introduced by DMM 
MUST be considered to be eliminated. 
Else the security protection would be degraded 
in the DMM solution versus in existing mobility protocols.
</t>
</list>
</t>

<t>
This requirement prevents a DMM solution 
from introducing uncontrollable problems 
of potentially insecure mobility management protocols 
which make deployment infeasible 
because platforms conforming to the protocols 
are at risk for data loss and numerous other dangers, 
including financial harm to the users. 
</t>

</section>

<!-- REQ7 -->
<section 
title="Multicast">
<t>
<list style='format REQ%d:' counter="R_count">
<t>
Multicast considerations
<vspace blankLines="1" />
DMM SHOULD consider multicast early 
so that solutions can be developed 
not only to provide IP mobility support
when it is needed, 
but also to avoid network inefficiency issues 
in multicast traffic delivery 
(such as duplicate multicast subscriptions
towards the downstream tunnel entities). 
The multicast solutions should therefore 
avoid restricting the management of all IP multicast traffic 
to a single host through a dedicated (tunnel) interface 
on multicast-capable access routers. 
<vspace blankLines="1" />
Motivation:
Existing multicast deployment have been introduced 
after completing the design of the reference mobility protocol, 
then optimization and extensions have been followed 
by "patching-up" procedure, 
thus leading to network inefficiency and non-optimal routing. 
The multicast solutions 
should therefore be required to consider efficiency nature 
in multicast traffic delivery.
</t>
</list>
</t>

<t>
This requirement addresses the problems 
PS1 and PS8 described in Section 4.
</t>


</section>

</section>


<section anchor="security" title="Security Considerations">
<t>
Please refer to the discussion 
under Security requirement in Section 5.6. 
</t>
</section>


<section title="IANA Considerations">
<t>None</t>
</section>


<section title="Co-authors and Contributors">
<t>This problem statement document is a joint effort 
among the numerous participants.
Each individual has made significant contributions 
to this work
and have been listed as co-authors. 
</t>

</section>

</middle>


<back>

<references title="Normative References">
  &rfc2119;
</references>

<references title="Informative References">
<?rfc include="reference.RFC.6275" ?>
<?rfc include="reference.RFC.5213" ?>
<?rfc include="reference.RFC.5380" ?>
<?rfc include="reference.RFC.5944" ?>
<?rfc include="reference.RFC.6301" ?>
<?rfc include="reference.RFC.3753" ?>
<?rfc include="reference.RFC.6909" ?>
<?rfc include="reference.RFC.6705" ?>
<?rfc include="reference.RFC.6224" ?>

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</references>

</back>
</rfc>

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