The document discusses Proxy Mobile IPv6, a standardized network-based mobility management protocol designed to facilitate seamless mobility for mobile nodes across various access technologies without requiring host participation. It outlines the protocol's features, such as inter-technology handoffs, multihoming support, and flow mobility support, which aim to enhance user experience while minimizing software requirements on mobile devices. Furthermore, the document highlights the need for this protocol as client-based mobility management solutions face significant adoption challenges in the current market.

1. Is Network-based Mobility Management
the Future?
by Sri Gundavelli
Abstract To overcome these shortcomings, IETF
recently standardized a network-based
ment. The protocol was designed with the
goal that the network will perform the mo-
Proxy Mobile IPv6 is a network-based
mobility management protocol, it is Proxy bility management on behalf of the client, it
mobility management protocol standard-
Mobile IPv6 [RFC-521]. Network-based will keep the client involvement to minimal
ized recently in IETF. This protocol is being
mobility management enables IP mobility proportions, such as allowing it to perform
referenced in various system architectures
for a host without requiring its participation inter-technology handoffs, or allowing it
such as a protocol for building a common
in any mobility related signaling. Net- to express handoff or flow preferences.
and access independent mobile core.
work-based mobility is another approach This design choice resulted in a simple
Currently, there are number of extensions
to solving the IP mobility problem. This client with minimal software requirements,
that are being specified for extending
approach for supporting mobility does not such as a connection manager which can
this protocol to support various mobility
require the mobile node to be involved perform these minimal required functions.
features. This document provides a brief
in the exchange of signaling messages The protocol was quickly adopted in GPP
overview of the protocol features and
between itself and the home agent. The and in WiMAX architectures on various
the deployment scenarios behind these
network is responsible for performing the interfaces and now many new extensions
features. Additionally, this document also
mobility management and a network node are being planned.
identifies the developmental efforts within
initiates the signaling with the home agent
Cisco for building the interfaces based
on Proxy Mobile IPv6 on Cisco’s mobile
on behalf of the mobile node. Mobile Devices and
gateway products. The protocol largely leveraged all the Access Networks
signaling and messaging semantics from Most of the mobile devices that are avail-
Introduction the Mobile IPv6 protocol, but chose the ap- able today in the market are equipped with
Mobile Communications is now a real- proach of network-based mobility manage- multiple radio interfaces. So, it is reason-
ity and is part of our daily lives. With the
explosive growth in the smart PDA devices
coupled with the ubiquitous availability of
access networks, IP Mobility is now a key
aspect of mobile communications and is
the next step in the Internet evolution. It is
practical now for a mobile node to roam
between different access technologies
and further it is reasonable to expect ad-
dress continuity and session persistence
across these handoffs.
With these requirements in anticipation,
Mobile IPv6 protocol [RFC-775] has been
developed by the IETF few years back.
It is a host-based mobility management
protocol requiring the participation of the
host in all aspects of mobility manage-
ment. However, this requirement of the host
participation in the mobility management
and the associated software and resource
requirements on the host has become a
primary hurdle for the protocol adoption.
IP NGN ARCHITECTURE THOUGHT LEADERSHIP JOURNAL - Q1 FY2010

2. able to assume that the mobile devices
that attach to the 4G networks in future
will also be equipped with multiple radio in-
terfaces, such as LTE, WiMAX, eHRPD, WiFi
etc, and in any combination. These mobile
nodes can potentially attach to the network
using one or more interfaces and be using
all of those interfaces simultaneously for its
data sessions.
It is given that the next generation mobile
networks will be true heterogeneous net-
works. A mobile operator can potentially be
managing more than one access technol-
ogy in their core network. Or, they may
have partnerships with other operators
that support a different access technology Figure 14 - Proxy Mobile IPv6 Domain
than what is supported in the operator’s
home network. For example, one SP may
have a nation-wide LTE network and may
have partnerships with other SPs for WiFi
mobile node moving from one base
station to another and using the same
Network-based Mobility
access in hotspots. Even for other reasons interface for its network attachment. Management Approach
such as during migration, an operator may
support a nation wide G network with one • Roaming in a heterogeneous network
The Proxy Mobile IPv6 protocol [RFC-
521] is designed with the goal of sup-
access technology while bringing up 4G – A mobile node should have the ability
porting the above requirements listed in
networks in some pockets; this would be to seamlessly roam between two dif-
Section 4.0. It is a protocol for providing
the natural migration for CDMA operators ferent access networks. For example, a
mobility management support to a mobile
from eHRPD to LTE. mobile node initially attached to an LTE
node without requiring its participation in
network, later when in the vicinity of a
Furthermore, these access networks can any mobility related signaling. The core
WiFi network, should have the ability to
be running any IP protocol version, such as functional entities of the protocol are the
perform an inter-technology handoff
the network could be IPv4-only, IPv6-only local mobility anchor (LMA) and the mobile
and move its IP address configuration
or IPv4/IPv6 capable. access gateway (MAG).
and all its network sessions to the WiFi
interface. The local mobility anchor is the home
The Mobility
Requirements • Multihoming Support – A mobile node
agent for the mobile node in the Proxy
Mobile IPv6 domain. It maintains the mobile
should have the ability to attach to
The anticipated mobile device capabilities node’s binding state and is the topological
network using multiple interfaces and
coupled with the availability of hetero- anchor point for the mobile node’s home
be able to use any one or more of its
geneous network with multiple access network prefix. The protocol introduces
interfaces for network connectivity.
technologies requires seamless mobility a new functional entity called the Mobile
support for providing any reasonable end- • Flow Mobility Support – A mobile node Access Gateway. It is the entity responsible
user experience. Following are the some of should have the ability to move the for detecting mobile node’s movements to
the mobility related considerations: flows between interfaces on a selec- and from the access link and for initiating
tive basis. For example, a mobile node signaling with the local mobility anchor.
• Roaming in a homogeneous network initially attached to an LTE network, later
Once the mobile node enters a Proxy
– A mobile node should have the abil- when in the vicinity of a WiFi network,
Mobile IPv6 domain and attaches to an
ity to seamlessly roam and change should have the ability to move certain
access link, the network allocates a unique
its point of attachment within a single high bandwidth intensive flows to the
home network prefix set for that attached
access technology domain. This is WiFI network.
interface. The mobile node will be able to
the case of a simple roaming with the
configure one or more addresses from
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3. The host can be a simple dual-stack termi-
nal. However, for supporting inter-technol-
ogy handoffs, the protocol places certain
assumptions on the host; specifically it
requires the host to have the ability to per-
form inter-technology handoffs. On most
operating systems, it can be achieved by
enabling virtual interface configuration on
the host, as shown below.
Client-based Mobility
Management Approach
Mobile IPv6 [RFC-775] with some of the
other extensions can be potentially used
for supporting these mobility requirements
Figure 15 - Inter-Technology Handoffs identified in Section 4.0. This requires the
mobile node to participate in all aspects
of mobility management. In addition to the
the assigned prefixes. If the mobile node sending a Proxy Binding Update (PBU) base Mobile IPv6 client support, it requires
connects to the Proxy Mobile IPv6 do- message. support for the following extensions:
main through multiple interfaces and over
multiple access networks, the network will • The local mobility anchor learns the • Dual-Stack Mobile IPv6 [ID-DSMIP6]
mobile node’s current point of attach- support is required for supporting
allocate a unique set of home network pre- dual-stack mobile nodes and also while
ment from the received Proxy Binding
fixes for each of the connected interfaces. roaming into an IPv4-only network.
Update. Upon accepting the request, it
The mobile node will be able to configure
the addresses on those interfaces from
assigns a home network prefix for the
mobile node’s attached interface and
• Multiple Care-of Address Registration
the respective home network prefixes. support [ID-MCOA6] is required for
establishes a tunnel with the mobile allowing the mobile node to use more
If the mobile node performs a handoff by access gateway. than one of its interfaces and establish
moving its address configuration from one
interface to the other (Ex: Moving from LTE • The mobile access gateway, then, ad- tunnels to the home agent.
to WiFI) and if the local mobility anchor
vertises the home prefix to the mobile
node over the point-to-point link. There-
• Additionally, the mobile node is re-
receives a handoff hint from the serving quired to support IPsec [RFC-401]
fore, the mobile node can auto-config- with IKEv2 [RFC-406] for securing the
mobile access gateway about the same,
ure one or more IPv6 addresses from signaling.
the local mobility anchor will assign the
its home network prefix.
same home network prefix that it previous- However, it is to be noted that the internet
ly assigned prior to the handoff. However, • Any time the mobile node changes its community is not in favor of supporting
this may require some special configura- point of attachment, the mobile access client-based mobility protocols for various
tion on the mobile node to ensure there is gateway on the new link will perform reasons.
no session loss during this handoff. the same sequence of operation and
The following are the typical sequence
ensure the mobile node can continue
to retain its address configuration on
The future of
of events that follows a mobile node’s
change of attachment in the Proxy Mobile
the new link. It will ensure the prefixes Client-based Mobility
IPv6 domain:
that are hosted on the new link are the
mobile node’s home network prefixes.
Management
For attempting to understand why there
• The mobile access gateway detects
For supporting the requirements identi- is a large internet community and vendor
the mobile node’s attachment on its link backing behind network-based mobility
fied in Section 4.0, the protocol does not
and initiates Proxy Mobile IPv6 signal- approaches, such as Proxy Mobile IPv6
require any special changes on the host.
ing with the local mobility anchor by [RFC-521] or Generic Tunneling Protocol
IP NGN ARCHITECTURE THOUGHT LEADERSHIP JOURNAL - Q1 FY2010

4. (GTP), it is important to review the current be supported in some of the integrated
deployment and tool availability status of dual-radio wireless chipsets, by at least
one of the key components in the client- one chip vendor, but that represents a
based mobility management protocol, the low and insignificant adoption rate.
Mobile IPv6 client [RFC-775]. Following
Thus, it is reasonable to assume that there
are some observations:
are significant challenges in pushing a cli-
• The Mobile IP client, Mobile IPv4 or Mo- ent-based mobility management approach
bile IPv6, is not shipped to-date as part which requires massive amount of devel-
of any of the major Operating Systems. opment efforts and $$ investment. Given
To name a few, its not part of any of the the fact that there is no vendor commit-
Microsoft Windows released versions, ment, no tools in the market and consider-
its not shipped with MAC OS/X, its not ing the number of years since some of
shipped with any of the standard Linux these specs have been standardized, it is
distributions (Fedora, Redhat, Ubuntu ..) reasonable to explore other approaches.
and is not shipped as part of any of the
Given the multitude of operating systems
BSD distributions.
and variants, it is not a trivial task to have
• Looking beyond the default Operating a Mobile IPv6 client that includes IKEv2,
System shipments, there are close to IPSec, Dual-Stack Mobile IPv6 and MCOA,
zero, or may be one or two commercial and have it tested across all these plat-
stack vendors. Further, expecting these forms and be available in the time frame
vendors to support the core mobility when the industry needs this work. This
components, Mobile IPv6 [RFC-775], may happen eventually, but for the current
Dual-Stack Mobile IPv6 [ID-DSMIP6], time frame, the market is looking for other
MCoA [ID-MCOA6], IKEv2 [RFC-406], solutions and network-based mobility is
IPsec [RFC-401] on all variants of the preferred approach which requires
Windows, Android, iPhone, Linux and minimal host support with an application
BSD systems requires a lot of effort, pa- module that any vendor can develop easily.
tience, faith and hope. However, it may May be Proxy Mobile IPv6, is the answer.
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Americas Headquarters Asia Pacific Headquarters Europe Headquarters
Cisco Systems, Inc. Cisco Systems (USA) Pte. Ltd. Cisco Systems International BV
San Jose, CA Singapore Amsterdam, The Netherlands
Cisco has more than 200 offices worldwide. Addresses, phone numbers, and fax numbers are listed on the Cisco Website at www.cisco.com/go/offices.
CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect, Cisco Stackpower, Cisco StadiumVision, Cisco TelePresence, Cisco WebEx, DCE, and Welcome to
the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn and Cisco Store are service marks; and Access Registrar, Aironet, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE,
CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation,
EtherFast, EtherSwitch, Event Center, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iPhone, iQuick Study, IronPort, the IronPort logo, LightStream, Linksys, MediaTone, MeetingPlace,
MeetingPlace Chime Sound, MGX, Networkers, Networking Academy, Network Registrar, PCNow, PIX, PowerPanels, ProConnect, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase
Your Internet Quotient, TransPath, WebEx, and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0903R)