One document matched: draft-chan-distributed-mobility-ps-00.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY rfc2119 PUBLIC ''
'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
]>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no"?>
<?rfc strict="yes"?>
<?rfc compact="yes" ?>
<?rfc subcompact="yes" ?>
<rfc category="info" ipr="trust200902"
docName="draft-chan-distributed-mobility-ps-00">
<front>
<title abbrev="DMM-PS">
Problem statement for distributed and dynamic mobility management
</title>
<author initials="H" surname="Chan (Ed.)" fullname="H Anthony Chan (editor)">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>1700 Alma Dr. Plano, TX 75075, USA</street>
<street>Email: h.a.chan@ieee.org</street>
<street>-</street>
<street>Dapeng Liu</street>
<street>China Mobile</street>
<street>Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China</street>
<street>Email: liudapeng@chinamobile.com</street>
<street>-</street>
<street>Pierrick Seite</street>
<street>France Telecom - Orange</street>
<street>4, rue du Clos Courtel, BP 91226, Cesson-Sevigne 35512, France</street>
<street>Email: pierrick.seite@orange-ftgroup.com</street>
<street>-</street>
<street>Hidetoshi Yokota</street>
<street>KDDI Lab</street>
<street>2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan</street>
<street>Email: yokota@kddilabs.jp</street>
<street>-</street>
<street>Charles E. Perkins</street>
<street>Tellabs Inc.</street>
<street>3590 N. 1st Street, Suite 300, San Jose, CA 95134, USA</street>
<street>Email: charles.perkins@tellabs.com</street>
<street>-</street>
<street>Melia Telemaco</street>
<street>Alcatel-Lucent Bell Labs</street>
<street>Email: telemaco.melia@alcatel-lucent.com</street>
<street>-</street>
<street>Wassim Michel Haddad</street>
<street>Ericsson</street>
<street>300 Holger Dr, San Jose, CA 95134, USA</street>
<street>Email: Wassam.Haddad@ericsson.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>Hui Deng</street>
<street>China Mobile</street>
<street>Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China</street>
<street>Email: denghui@chinamobile.com</street>
<street>-</street>
<street>Zhen Cao</street>
<street>China Mobile</street>
<street>Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China</street>
<street>Email: caozhen@chinamobile.com</street>
<street>-</street>
</postal>
</address>
</author>
<date month="October"year="2010"/>
<area></area>
<workgroup></workgroup>
<abstract>
<t>
Mobility solutions deployed with centralized mobility anchoring
in existing hierarchical mobile networks
are more prone to the following problems or limitations
compared with distributed and dynamic mobility management:
(1) Routing via a centralized anchor is often longer,
so that those mobility protocol deployments
that lack optimization extensions
results in non-optimal routes,
affecting performance;
whereas routing optimization may be an integral part
of a distributed design.
(2) As mobile network becomes more flattened
centralized mobility management
can become more non-optimal,
especially as the content servers in a content delivery network (CDN)
are moving closer to the access network;
in contrast,
distributed mobility management
can support both hierarchical network and more flattened network
as it also supports CDN networks.
(3) Centralized route maintenance and context maintenance
for a large number of mobile hosts is more difficult to scale.
(4) Scalability may worsen
when lacking mechanism
to distinguish whether there are real need for mobility support;
dynamic mobility management,
i.e., to selectively provide mobility support,
is needed
and may be better implemented with distributed mobility management.
(5) Deployment is complicated
with numerous variants and extensions of mobile IP;
these variants and extensions may be better integrated
in a distributed and dynamic design
which can selectively adapt to the needs.
(6) Excessive signaling overhead should be avoided
when end nodes are able to communicate end-to-end;
capability to selectively turn off signaling that are not needed by the end hosts
will reduce the handover delay.
(7) Centralized approach is generally
more vulnerable to a single point of failure and attack
often requiring duplication and backups,
whereas a distributed approach
intrinsically mitigates the problem to a local network
so that the needed protection can be simpler.
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>
In the past decade a fair number of mobility protocols have been standardized.
Although the protocols differ
in terms of functions and associated message format,
we can identify a few key common features:
<list>
<t>
presence of a centralized mobility anchor
providing global reachability and an always-on experience;
</t>
<t>
extensions to optimize handover performance
while users roam across wireless cells;
</t>
<t>
extensions to enable the use of heterogeneous wireless interfaces
for multi-mode terminals (e.g. cellular phones).
</t>
</list>
The presence of the centralized mobility anchor
allows a mobile device to be reachable
when it is not connected to its home domain.
The anchor, among other tasks,
ensures forwarding of packets destined to or sent from the mobile device.
As such, most of the deployed architectures today
have a small number of centralized anchors
managing the traffic of millions of mobile subscribers.
Coompared with a distributed approach,
a centralized approach have several issues or limitations
affecting performance and scalability,
which require costly network dimensioning
and engineering to fix them.
</t>
<t>
To optimize handovers for mobile users,
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 impose stringent requirements in terms of delay.
Notions of localization and distribution of local agents
have been introduced to reduce signalling overhead.
Unfortunately today we witness difficulties in getting such protocols deployed,
often leading to sub-optimal choices.
</t>
<t>
Moreover, all the availability of multi-mode devices
and the possibility to use several network interfaces simultaneously
have motivated the development of more new protocol extensions.
Deployment will be further complicated with so many extensions.
</t>
<t>
Mobile users are, more than ever, consuming Internet content,
and impose new requirements on mobile core networks for data traffic delivery.
When this traffic demand exceeds available capacity,
service providers need to implement new strategies
such as selective traffic offload (e.g. 3GPP work items LIPA/SIPTO)
through alternative access networks (e.g. WLAN).
Moreover, the localization of content providers
closer to the Mobile/Fixed Internet Service Providers network
requires taking into account local Content Delivery Networks (CDNs)
while providing mobility services.
</t>
<t>
As long as demand exceeds capactity,
both offloading and CDN techniques
could benefit from the development of more flat mobile architectures
(i.e., fewer levels of routing hierarchy
introduced into the data path by the mobility management system).
This view is reinforced by the shift in users¡¯ traffic behavior,
aimed at increasing direct communications among peers
in the same geographical area.
The development of truly flat mobile architectures
would result in anchoring the traffic
closer to point of attachment of the user
and overcoming the suboptimal routing issues of a centralized mobility scheme.
</t>
<t>
While deploying [Paper-Locating.User] today¡¯s mobile networks,
service providers face new challenges.
More often than not,
mobile devices remain attached to the same point of attachment,
in which case specific IP mobility management support
is not required for applications
that launch and complete while connected to the same point of attachment.
However,
the mobility support has been designed to be always on
and to maintain the context for each mobile subscriber
as long as they are connected to the network.
This can result in a waste of resources
and ever-increasing costs for the service provider.
Infrequent mobility and intelligence of many applications
suggest that mobility can be provided dynamically,
thus simplifying the context maintained
in the different nodes of the mobile network.
</t>
<t>
The proposed work will address two complementary aspects
of mobility management procedures:
the distribution of mobility anchors to achieve a more flat design
and the dynamic activation/deactivation of mobility protocol support
as an enabler to distributed mobility management.
The former has the goal of positioning mobility anchors (HA, LMA)
closer to the user;
ideally, these mobility agents could be collocated with the first hop router.
The latter, facilitated by the distribution of mobility anchors,
aims at identifying when mobility must be activated
and identifying sessions that do not impose mobility management
-- thus reducing the amount of state information
to be maintained in the various mobility agents of the mobile network.
The key idea is that dynamic mobility management relaxes some constraints
while also repositioning mobility anchors;
it avoids the establishment of non optimal tunnels
between two anchors topologically distant.
</t>
<t>
This document discusses the issues
with centralized IP mobility management
compared with distributed and dynamic mobility management.
A companion document [dmm-senario]
discusses the use case senarios.
</t>
</section>
<section title="Conventions used in this document">
<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>
</section>
<section title="Centralized versus distributed mobility management">
<t>
Mobility management functions
may be implemented at different layers
of the OSI stack.
At the IP layer,
they may reside in the network or in the mobile node.
In particular,
network-based solution resides in the network only.
It therefore enables mobility for hosts
and network applications
which lack mobility support in them
but are already in deployment.
</t>
<t>
At the IP layer,
a mobility management protocol to achieve session continuity
are typically based on the principle
of distinguishing between session identifier and routing address
and maintaining a mapping between them.
With Mobile IP, the home address takes the role of session identifier
whereas the care-of-address takes the role of routing address,
and the binding between them is maintained at the mobility anchor,
i.e., the home agent.
</t>
<t>
Mobility management functions in the network
may be centralized or distributed,
as is explained in the next two subsections.
</t>
<section title="Centralized mobility management">
<t>
With centralized mobility management,
the mapping information is kept at a centralized mobility anchor,
and packets destined to the mobile node are routed via this anchor.
That is, such mobility management systems are centralized
in both the data plane and the control plane.
</t>
<t>
Existing mobility solutions leverage on centralized mobility anchoring
in a hierarchical architecture.
Examples of such centralized mobility anchors
are the home agent (HA) and local mobility anchor (LMA)
in mobile IP
<xref target="RFC3775"/>
and proxy mobile IP
<xref target="RFC5213"/>
respectively.
Current mobile networks such as UMTS network, CDMA network,
and 3GPP SAE network
also use centralized mobility management.
</t>
<figure>
<preamble></preamble>
<artwork><![CDATA[
UMTS 3GPP SAE MIP/PMIP
+------+ +------+ +------+
| GGSN | | P-GW | |HA/LMA|
+------+ +------+ +------+
/\ /\ /\
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
+------+ +------+ +------+ +------+ +------+ +------+
| SGSN | | SGSN | | S-GW | | S-GW | |FA/MAG| |FA/MAG|
+------+ +------+ +------+ +------+ +------+ +------+
]]></artwork>
<postamble></postamble>
</figure>
<t>Figure 1. Centralized mobility management.
</t>
</section>
<section title="Distributed mobility management">
<t>The mobility management functions may be distributed
to multiple locations in different networks,
so that a mobile node in any of these networks
may be served by a close by 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>
Distributed mobility management may be partially distributed,
i.e., only the data plane is distributed,
or fully distributed
where both data plane and control plane are distributed.
These different approaches are described in [I-D.dmm-scenario].
</t>
</section>
</section>
<section title="Problem statement">
<t>This section describes the problems or limitations
in a centralized mobility approach
and compares it against the distributed approach.
</t>
<section title="Non-optimal routes">
<t>Routing via a centralized anchor often results in a longer route.
Figure 3 shows two cases of non-optimized routes.
In the first case, the mobile node and the correspondent node
are close to each other but are both far from the mobility anchor.
In the second case, the mobile node is getting content
from a local content delivery network (CDN).
In both cases,
packets destined to the MN have to be routed via the mobility anchor,
which is not in the shortest path.
</t>
<figure>
<preamble></preamble>
<artwork><![CDATA[
MIP/PMIP
+------+
|HA/LMA|
+------+
/\ \ \ +---+
/ \ \ \ |CDN|
/ \ \ \ +---+
/ \ \ \ |
/ \ \ \ |
+------+ +------+ +------+ +------+
|FA/MAG| |FA/MAG| |FA/MAG| |FA/MAG|
+------+ +------+ +------+ +------+
| |
---- ----
| CN | | MN |
---- ----
]]></artwork>
<postamble></postamble>
</figure>
<t>Figure 3. Non-optimized route when communicating with CN
and when accessing local content.
</t>
<t>In a distributed mobility management design,
there are numerous anchors in different networks
so that packets may be routed via a nearby mobility function,
as shown in Figure 4.
</t>
<figure>
<preamble></preamble>
<artwork><![CDATA[
+---+
|CDN|
+---+
|
|
+------+ +------+ +------+ +------+
| MF | | MF | | MF | | MF |
+------+ +------+ +------+ +------+
| |
---- ----
| CN | | MN |
---- ----
]]></artwork>
<postamble></postamble>
</figure>
<t>Figure 4.
Mobile node in any network is served by a close by mobility function.
</t>
<t>
With the centralized mobility anchor design,
route optimization extensions to mobility protocols
are therefore needed,
and those mobility protocol deployments
that lack such optimization extensions
will encounter non-optimal routes,
which affect performance.
In contrast,
route optimization may be an integral part of a distributed design.
</t>
</section>
<section title="Network architecture evolution">
<t>
The centralized mobility management
is currently deployed to support the existing hierarchical networks.
It leverages on the hierarchical architecture.
However,
the volume of wireless data traffic
continues to increase exponentially.
The data traffic increase
would require too much costly capacity upgrade
of centralized architectures.
It is thus predictable
that the data traffic increase will soon overload
the centralized data anchor point, e.g., P-GW in 3GPP/SAE.
In order to address this issue,
a trend in the evolution of mobile networks
is to distribute the network functions
close to the access gateways.
These network functions can be the content servers
in a Content Delivery Network (CDN) but also the data anchor point.
</t>
<t>
As mobile network becomes more flattened
the centralized mobility management can become non-optimal.
</t>
<t>
Mobility management deployment with distributed architecture
is then needed
to support the more flattened network
and the CDN networks.
In addition, such distributed design
may likely be able to also support the hierarchical network.
</t>
</section>
<section title="Centralized route and mobility context maintenance">
<t>
Routes are set up to enable session continuity when handover occurs.
Mobility contexts are also maintained to route via a mobility anchor.
</t>
<t>Setting up such routes and maintaining the mobility context
is more difficult to scale
in a centralized design
with a large number of mobile hosts.
Distributing the route maintenance function
and the mobility context maintenance function
among different networks can be more scalable.
</t>
</section>
<section title="Need versus no need for mobility support">
<t>
The problem of centralized route and mobility context maintenance
is aggravated
when the via routes are set up
for many more mobile nodes
that are not going to physically move out of a radio cell.
For example, the user may be communicating at home,
in one's office, or at a cafe.
Much more resources are also wasted
to maintain the mobility context of these routes.
Similarly, intelligent applications
that do not need network-layer mobility support
coexist with applications lacking such intelligence.
</t>
<t>
Dynamic mobility management,
i.e., to dynamically set up the via routes
only for mobile nodes that actually undergoes handover
and lacks higher-layer mobility support,
is needed.
With distributed mobility anchors,
the mechanism to support dynamic mobility may then also be distributed.
Therefore,
dynamic mobility and distributed mobility may complement each other
and may be integrated.
</t>
</section>
<section title="Numerous variants and extensions of MIP">
<t>
Mobile IP (MIP) already has numerous variants and extensions
including PMIP, FMIP, HMIP,
and there may be more to come.
Deployment can then become complicated,
especially if interoperability
with existing deployments is an issue.
</t>
<t>
Because the distributed mobility management
needs to work both
with network architectures of hierarchical networks
as well as flattened networks,
our design needs to be flexible enough to support different networks.
In addition, one goal of dynamic mobility management
is the capability to selectively turn on and off mobility support
and certain different mobility signaling.
Such flexibility in the design provides a good foundation
to integrate the different mobility variants.
Some additional extensions to the base protocols
may then be needed to improve the integration.
</t>
</section>
<section title="Peer-to-peer communication">
<t>
As MIPv6 Route Optimization (RO) mode
enables a more efficient data packets exchange
than the bidirectional tunneling (BT) mode,
it is expected to be used whenever possible
unless the mobile node is not interested
in disclosing its topological location,
i.e., care-of address, for the CN
(e.g., for privacy reasons)
or some other network constraints are put in place.
</t>
<t>
However,
MIPv6 RO mode requires
exchanging a significant amount of signaling messages
in order to establish,
and periodically refresh a bidirectional security association (BSA)
between the mobile node and the correspondent node (CN).
While the mobility signaling exchange
impacts the overall handoff latency,
the BSA is needed to authenticate the binding update
and acknowledgment messages (note that the latter is not mandatory).
In addition,
the amount of mobility signaling messages increases further
when both endpoints are mobile.
</t>
<t>
A dynamic mobility management capability
to turn off these signaling when they are not needed
will enable the RO mode between two mobile endpoints
at minimum or no cost.
It will reduce the handoff latency
owing to the removal of the extra signaling.
It will encourage its adoption and large scale deployment.
</t>
</section>
<section title="Single point of failure and attack">
<t>
A centralized anchoring architecture
is generally more vulnerable
to a single point of failure or attack,
requiring duplication and backups of the support functions.
</t>
<t>
A distributed mobility management architecture
has intrinsically mitigated the problem
to a local network which is then of a smaller scope.
In addition,
the availability of such functions in neighboring networks
has already provided the needed architecture to support protection.
</t>
</section>
</section>
<section anchor="security" title="Security Considerations">
<t>TBD</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 following participants in a design team.
Each individual has made significant contributions to this work.
</t>
<t>Dapeng Liu: liudapeng@chinamobile.com</t>
<t>Pierrick Seite: pierrick.seite@orange-ftgroup.com</t>
<t>Hidetoshi Yokota: yokota@kddilabs.jp</t>
<t>Charles E. Perkins: charles.perkins@tellabs.com</t>
<t>Melia Telemaco: telemaco.melia@alcatel-lucent.com</t>
<t>Hui Deng: denghui@chinamobile.com</t>
<t>Elena Demaria: elena.demaria@telecomitalia.it</t>
<t>Zhen Cao: caozhen@chinamobile.com</t>
<t>Wassim Michel Haddad: Wassam.Haddad@ericsson.com</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc2119;
</references>
<references title="Informative References">
<?rfc include="reference.RFC.3775" ?>
<?rfc include="reference.RFC.5213" ?>
<reference anchor="I-D.dmm-scenario">
<front>
<title>Use case scenarios for Distributed Mobility Management</title>
<author initials="H" surname="Yokota" fullname="Hidetoshi Yokota">
<organization />
</author>
<author initials="P" surname="Seite" fullname="Pierrick Seite">
<organization />
</author>
<author initials="E" surname="Demaria" fullname="Elena Demaria">
<organization />
</author>
<author initials="Z" surname="Cao" fullname="Zhen Cao">
<organization />
</author>
<date month="October" year="2010" />
</front>
<seriesInfo name="Internet-Draft" value="draft-yokota-dmm-scenario-00" />
<format type="TXT" target="http://www.ietf.org/internet-drafts/draft-yokota-dmm-scenario-00.txt" />
</reference>
<reference anchor="Paper-Locating.User">
<front>
<title>Locating the User</title>
<author initials="G" surname="Kirby">
<organization />
</author>
<date year="1995" />
</front>
<seriesInfo name="" value="Communication International" />
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 21:40:17 |