Network Working Group H. Chan (Ed.)
Internet-Draft Huawei Technologies
Intended status: Informational June 8, 2012
Expires: December 10, 2012
Requirements of distributed mobility management
draft-chan-dmm-requirements-01
Abstract
The traditional hierarchical structure of cellular networks has led
to deployment models which are heavily centralized. Mobility
management with centralized mobility anchoring in existing
hierarchical mobile networks is quite prone to suboptimal routing and
issues related to scalability. Centralized functions present a
single point of failure, and inevitably introduce longer delays and
higher signaling loads for network operations related to mobility
management. This document defines the requirements for distributed
mobility management for IPv6 deployment. The objectives are to match
the mobility deployment with the current trend in network evolution,
to improve scalability, to avoid single point of failure, to enable
transparency to upper layers only when needed, etc. The distributed
mobility management also needs to be compatible with existing network
deployments and end hosts, and be secured.
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Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 5
3. Centralized versus distributed mobility management . . . . . . 5
3.1. Centralized mobility management . . . . . . . . . . . . . 6
3.2. Distributed mobility management . . . . . . . . . . . . . 7
4. Problem statement . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Non-optimal routes . . . . . . . . . . . . . . . . . . . . 9
4.2. Non-optimality in Evolved Network Architecture . . . . . . 10
4.3. Low scalability of centralized route and mobility
context maintenance . . . . . . . . . . . . . . . . . . . 11
4.4. Single point of failure and attack . . . . . . . . . . . . 12
4.5. Wasting resources to support mobile nodes not needing
mobility support . . . . . . . . . . . . . . . . . . . . . 12
4.6. Other related problems . . . . . . . . . . . . . . . . . . 13
4.6.1. Mobility signaling overhead with peer-to-peer
communication . . . . . . . . . . . . . . . . . . . . 13
4.6.2. Complicated deployment with too many variants and
extensions of MIP . . . . . . . . . . . . . . . . . . 14
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1. Distributed deployment . . . . . . . . . . . . . . . . . . 15
5.2. Transparency to Upper Layers when needed . . . . . . . . . 15
5.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 15
5.4. Compatibility . . . . . . . . . . . . . . . . . . . . . . 16
5.5. Existing mobility protocols . . . . . . . . . . . . . . . 16
5.6. Security considerations . . . . . . . . . . . . . . . . . 17
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Co-authors and Contributors . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
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:
presence of a centralized mobility anchor providing global
reachability and an always-on experience;
extensions to optimize handover performance while users roam
across wireless cells;
extensions to enable the use of heterogeneous wireless interfaces
for multi-mode terminals (e.g. cellular phones).
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 point, among other tasks, ensures reachability of
forwarding of packets destined to or sent from the mobile device.
Most of the deployed architectures today have a small number of
centralized anchors managing the traffic of millions of mobile
subscribers. Compared with a distributed approach, a centralized
approach is likely to have several issues or limitations affecting
performance and scalability, which require costly network
dimensioning and engineering to resolve.
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 impose stringent requirements in
terms of delay. Notions of localization and distribution of local
agents have been introduced to reduce signaling overhead.
Unfortunately today we witness difficulties in getting such protocols
deployed, often leading to sub-optimal choices.
Moreover, the availability of multi-mode devices and the possibility
of using several network interfaces simultaneously have motivated the
development of more new protocol extensions. Deployment is further
complicated with so many extensions.
Mobile users are, more than ever, consuming Internet content; such
traffic imposes new requirements on mobile core networks for data
traffic delivery. When the 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
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Providers network requires taking into account local Content Delivery
Networks (CDNs) while providing mobility services.
When demand exceeds capacity, both offloading and CDN techniques
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 in network flattening is
reinforced by a shift in users traffic behavior, aimed at increasing
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 and overcome the suboptimal routing issues of a centralized
mobility scheme.
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. Specific IP
mobility management support is not required for applications that
launch and complete while the mobile device is 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.
The proposed charter 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 topologically
distant anchors.
Considering the above, the distributed mobility management working
group is chartered with the following tasks:
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Define the problem statement of distributed mobility management
and identity the requirements for a distributed mobility
management solution.
Document practices for the deployment of existing mobility
protocols in a distributed mobility management environment.
Identify the limitations in the current practices with respect to
providing the expected functionality.
If limitations are identified as part of the above deliverable,
specify extensions to existing protocols that removes these
limitations within a distributed mobility management environment.
This document describes the motivations of distributed mobility
management and the proposed work in Section 1.1. Section 1.2
summarizes the problems with centralized IP mobility management
compared with distributed and dynamic mobility management, which is
elaborated in Section 4. The requirements to address these problems
are given in Section 5. A companion document [I-D.yokota-dmm-
scenario] discusses the use case scenarios.
Much of the problems explained in this document together with the
contents in [I-D.yokota-dmm-scenario] have been merged and elaborated
into the following review paper: [Paper-Distributed.Mobility.Review].
2. Conventions used in this document
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 [RFC2119].
3. Centralized versus distributed mobility management
Mobility management functions may be implemented at different layers
of the network protocol stack. At the IP (network) layer, they may
reside in the network or in the mobile node. In particular, a
network-based solution resides in the network only. It therefore
enables mobility for existing hosts and network applications which
are already in deployment but lack mobility support.
At the IP layer, a mobility management protocol to achieve session
continuity is typically based on the principle of distinguishing
between identifier and routing address and maintaining a mapping
between them. With Mobile IP, the home address serves as an
identifier of the device whereas the care-of-address takes the role
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of routing address, and the binding between them is maintained at the
mobility anchor, i.e., the home agent. If packets can be
continuously delivered to a mobile device at its home address, then
all sessions using that home address can be preserved even though the
routing or care-of address changes.
The next two subsections explain centralized and distributed mobility
management functions in the network.
3.1. Centralized mobility management
With centralized mobility management, the mapping information between
the stable node identifier and the changing IP address of a mobile
node (MN) is kept at a centralized mobility anchor. Packets destined
to an MN are routed via this anchor. In other words, such mobility
management systems are centralized in both the control plane and the
data plane.
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
[RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively. Current
mobile networks such as the Third Generation Partnership Project
(3GPP) UMTS networks, CDMA networks, and 3GPP Evolved Packet System
(EPS) networks also employ centralized mobility management, with
Gateway GPRS Support Node (GGSN) and Serving GPRS Support Node (SGSN)
in the 3GPP UMTS hierarchical network and with Packet data network
Gateway (P-GW) and Serving Gateway (S-GW) in the 3GPP EPS network.
UMTS 3GPP SAE MIP/PMIP
+------+ +------+ +------+
| GGSN | | P-GW | |HA/LMA|
+------+ +------+ +------+
/\ /\ /\
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
+------+ +------+ +------+ +------+ +------+ +------+
| SGSN | | SGSN | | S-GW | | S-GW | |FA/MAG| |FA/MAG|
+------+ +------+ +------+ +------+ +------+ +------+
Figure 1. Centralized mobility management.
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3.2. Distributed mobility management
Mobility management functions may also be distributed to multiple
locations in different networks as shown in Figure 2, so that a
mobile node in any of these networks may be served by a closeby
mobility function (MF).
+------+ +------+ +------+ +------+
| MF | | MF | | MF | | MF |
+------+ +------+ +------+ +------+
|
----
| MN |
----
Figure 2. Distributed mobility management.
Mobility management may be partially distributed, i.e., only the data
plane is distributed, or fully distributed where both the data plane
and control plane are distributed. These different approaches are
described in detail in [I-D.yokota-dmm-scenario].
[Paper-New.Perspective] discusses some initial steps towards a clear
definition of what mobility management may be, to assist in better
developing distributed architecture. [Paper-
Characterization.Mobility.Management] analyses current mobility
solutions and proposes an initial decoupling of mobility management
into well-defined functional blocks, identifying their interactions,
as well as a potential grouping, which later can assist in deriving
more flexible mobility management architectures. According to the
split functional blocks, this paper proposes three ways into which
mobility management functional blocks can be groups, as an initial
way to consider a better distribution: location and handover
management, control and data plane, user and access perspective.
A distributed mobility management scheme is proposed in [Paper-
Distributed.Dynamic.Mobility] for future flat IP architecture
consisting of access nodes. The benefits of this design over
centralized mobility management are also verified through simulations
in [Paper-Distributed.Centralized.Mobility].
Before designing new mobility management protocols for a future flat
IP architecture, one should first ask whether the existing mobility
management protocols that have already been deployed for the
hierarchical mobile networks can be extended to serve the flat IP
architecture. MIPv4 has already been deployed in 3GPP2 networks, and
PMIPv6 has already been adopted in WiMAX Forum and in 3GPP standards.
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Using MIP or PMIP for both centralized and distributed architectures
would ease the migration of the current mobile networks towards a
flat architecture. It has therefore been proposed to adapt MIP or
PMIPv6 to achieve distributed mobility management by using a
distributed mobility anchor architecture.
In [Paper-Migrating.Home.Agents], the HA functionality is copied to
many locations. The HoA of all MNs are anycast addresses, so that a
packet destined to the HoA from any corresponding node (CN) from any
network can be routed via the nearest copy of the HA. In addition,
distributing the function of HA using a distributed hash table
structure is proposed in [Paper-Distributed.Mobility.SAE]. A lookup
query to the hash table will retrieve the location information of an
MN is stored.
In [Paper-Distributed.Mobility.PMIP], only the mobility routing (MR)
function is duplicated and distributed in many locations. The
location information for any MN that has moved to a visited network
is still centralized and kept at a location management (LM) function
in the home network of the MN. The LM function at different networks
constitutes a distributed database system of all the MNs that belong
to any of these networks and have moved to a visited network. The
location information is maintained in the form of a hierarchy: the LM
at the home network, the CoA of the MR of the visited network, and
then the CoA to reach the MN in the visited network. The LM in the
home network keeps a binding of the HoA of the MN to the CoA of the
MR of the visited network. The MR keeps the binding of the HoA of
the MN to the CoA of the MN in the case of MIP, or the proxy-CoA of
the Mobile Access Gateway (MAG) serving the MN in the case of PMIP.
[I-D.jikim-dmm-pmip] discusses two distributed mobility control
schemes using the PMIP protocol: Signal-driven PMIP (S-PMIP) and
Signal-driven Distributed PMIP (SD-PMIP). S-PMIP is a partially
distributed scheme, in which the control plane (using a Proxy Binding
Query to get the Proxy-CoA of the MN) is separate from the data
plane, and the optimized data path is directly between the CN and the
MN. SD-PMIP is a fully distributed scheme, in which the Proxy
Binding Update is not performed, and instead each MAG will multicast
a Proxy Binding Query message to all of the MAGs in its local PMIP
domain to retrieve the Proxy-CoA of the MN.
4. Problem statement
This section identifies problems and limitations of centralized
mobility approaches, and compares against possible distributed
approaches. A few other related problems that may not be specific to
the centralized approach are also described.
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4.1. Non-optimal routes
PS1: Routing via a centralized anchor often results in a longer
route, and the problem is especially manifested when accessing
a local or cache server of a Content Delivery Network (CDN).
Figure 3 shows two cases of non-optimized routes.
MIP/PMIP
+------+
|HA/LMA|
+------+
/\ \ \ +---+
/ \ \ \ |CDN|
/ \ \ \ +---+
/ \ \ \ |
/ \ \ \ |
+------+ +------+ +------+ +------+
|FA/MAG| |FA/MAG| |FA/MAG| |FA/MAG|
+------+ +------+ +------+ +------+
| |
---- ----
| CN | | MN |
---- ----
Figure 3. Non-optimized route when communicating with a CN and when
accessing a local or cache server of a CDN.
In the first case, the mobile node and the correspondent node are
close to each other but are both far from the mobility anchor.
Packets destined to the mobile node need to be routed via the
mobility anchor, which is not on the shortest path. The second case
involves a content delivery network (CDN). A user may obtain content
from a server, such as when watching a video. As such usage becomes
more popular, resulting in an increase in the core network traffic,
service providers may relieve the core network traffic by placing
these contents closer to the users in the access network in the form
of cache or local CDN servers. Yet as the MN is getting content from
a local or cache server of a CDN, even though the server is close to
the MN, packets still need to go through the core network to route
via the mobility anchor in the home network of the MN, if the MN uses
the HoA as its identifier.
In a distributed mobility management design, one possibility is to
have mobility anchors distributed in different access networks so
that packets may be routed via a nearby mobility anchor function, as
shown in Figure 4.
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+---+
|CDN|
+---+
|
|
+------+ +------+ +------+ +------+
| MF | | MF | | MF | | MF |
+------+ +------+ +------+ +------+
| |
---- ----
| CN | | MN |
---- ----
Figure 4. Mobile node in any network is served by a close by
mobility function.
Due to the above limitation, with the centralized mobility anchor
design, route optimization extensions to mobility protocols are
therefore needed. Whereas the location privacy of each MN may be
compromised when the CoA of an MN is given to the CN, those mobility
protocol deployments that lack such optimization extensions will
encounter non-optimal routes, which affect the performance.
In contrast, route optimization may be naturally an integral part of
a distributed mobility management design. With the help of such
intrinsic route optimization, the data transmission delay will be
reduced, by which the data transmission throughputs can be enhanced.
Furthermore, the data traffic overhead at the mobility agents such as
the HA and the LMA in the core network can be alleviated
significantly.
4.2. Non-optimality in Evolved Network Architecture
PS2: The centralized mobility management can become non-optimal as a
network architecture evolves and becomes more flattened.
Centralized mobility management is currently deployed to support the
existing hierarchical mobile data networks. It leverages on the
hierarchical architecture. However, the volume of wireless data
traffic continues to increase exponentially. The data traffic
increase would require 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., the P-GW
in 3GPP EPS. In order to address this issue, a trend in the
evolution of mobile networks is to distribute network functions close
to access networks. These network functions can be the content
servers in a CDN, and also the data anchor point.
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Mobile networks have been evolving from a hierarchical architecture
to a more flattened architecture. In the 3GPP standards, the GPRS
network has the hierarchy GGSN "C SGSN "C RNC "C NB (Node B). In
3GPP EPS networks, the hierarchy is reduced to P-GW "C S-GW "C eNB
(Evolved NB). In some deployments, the P-GW and the S-GW are
collocated to further reduce the hierarchy. Reducing the hierarchy
this way reduces the number of different physical network elements in
the network, contributing to easier system maintenance and lower
cost. As mobile networks become more flattened, the centralized
mobility management can become non-optimal. Mobility management
deployment with distributed architecture is then needed to support
the more flattened network and the CDN networks.
4.3. Low scalability of centralized route and mobility context
maintenance
PS3: Setting up such special routes and maintaining the mobility
context for each MN is more difficult to scale in a centralized
design with a large number of MNs. Distributing the route
maintenance function and the mobility context maintenance
function among different networks can be more scalable.
Special routes are set up to enable session continuity when a
handover occurs. Packets sent from the CN need to be tunneled
between the HA and FA in MIP and between the LMA and MAG in PMIP.
However, these network elements at the ends of the tunnel are also
routers performing the regular routing tasks for ordinary packets not
involving a mobile node. These ordinary packets need to be directly
routed according to the routing table in the routers without
tunneling. Therefore, the network must be able to distinguish those
packets requiring tunneling from the regular packets. For each
packet that requires tunneling owing to mobility, the network will
encapsulate it with a proper outer IP header with the proper source
and destination IP addresses. The network therefore needs to
maintain and manage the mobility context of each MN, which is the
relevant information needed to characterize the mobility situation of
that MN to allow the network to distinguish their packets from other
packets and to perform the required tunneling.
Setting up such special routes and maintaining the mobility context
for each MN is more difficult to scale in a centralized design with a
large number of MNs. Distributing the route maintenance function and
the mobility context maintenance function among different networks
can be more scalable.
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4.4. Single point of failure and attack
PS4: Centralized anchoring may be more vulnerable to single point of
failure and attack than a distributed system.
A centralized anchoring architecture is generally more vulnerable to
a single point of failure or attack, requiring duplication and
backups of the support functions.
On the other hand, 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.
4.5. Wasting resources to support mobile nodes not needing mobility
support
PS5: IP mobility support is not always required. For example, some
applications do not need a stable IP address during handover,
i.e., IP session continuity. Sometimes, the entire application
session runs while the terminal does not change the point of
attachment. In these situations that do not require IP
mobility support, network resources are wasted when mobility
context is set up.
The problem of centralized route and mobility context maintenance is
aggravated when the via routes are set up for many more MNs that are
not requiring IP mobility support. On the one hand, the network
needs to provide mobility support for the increasing number of mobile
devices because the existing mobility management has been designed to
always provide such support as long as a mobile device is attached to
the network. On the other hand, many nomadic users are connected to
a network in an office or meeting room. Such users will not move for
the entire network session. It has been measured that over two-
thirds of a user mobility is local [Paper-Locating.User]. In
addition, it is possible to have the intelligence for applications to
manage mobility without needing help from the network. Network
resources are therefore wasted to provide mobility support for the
devices that do not really need it at the moment.
It is necessary to dynamically set up the via routes only for MNs
that actually undergo handovers and lack higher-layer mobility
support. With distributed mobility anchors, such dynamic mobility
management mechanism may then also be distributed. Therefore,
dynamic mobility and distributed mobility may complement each other
and may be integrated.
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4.6. Other related problems
Other related problems that may not be specifically owing to a
centralized architecture but are desirable to solve are described in
this subsection.
4.6.1. Mobility signaling overhead with peer-to-peer communication
O-PS1: Wasting resources when mobility signaling (e.g., maintenance
of the tunnel, keep alive, etc.) is not turned off for peer-
to-peer communication.
In peer-to-peer communications, end users communicate by sending
packets directly addressed to each other's IP address. However, they
need to find each other's IP address first through signaling in the
network. While different schemes for this purpose may be used, MIP
already has a mechanism to locate an MN and may be used in this way.
In particular, MIPv6 Route Optimization (RO) mode enables a more
efficient data packets exchange than the bidirectional tunneling (BT)
mode, as shown in Figure 5.
MIP/PMIP
+------+
|HA/LMA|
+------+
/\ \ \
/ \ \ \
/ \ \ \
/ \ \ \
/ \ \ \
+------+ +------+ +------+ +------+
|FA/MAG| |FA/MAG| |FA/MAG| |FA/MAG|
+------+ +------+ +------+ +------+
| |
---- ----
| MN |<--->| CN |
---- ----
Figure 5. Non-optimized route when communicating with CN and when
accessing local content.
This RO mode is expected to be used whenever possible unless the MN
is not interested in disclosing its topological location, i.e., the
CoA, to the CN (e.g., for privacy reasons) or some other network
constraints are put in place. However, MIPv6 RO mode requires
exchanging a significant amount of signaling messages in order to
establish and periodically refresh a bidirectional security
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association (BSA) between an MN and its CN. While the mobility
signaling exchange impacts the overall handover 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.
A dynamic mobility management capability that turns off these
signaling when they are not needed will enable the RO mode between
two mobile endpoints at minimum or no cost. It will also reduce the
handover latency owing to the removal of the extra signaling. These
benefits for peer-to-peer communications will encourage the adoption
and large-scale deployment of dynamic mobility management.
4.6.2. Complicated deployment with too many variants and extensions of
MIP
O-PS2: Deployment is complicated with many variants and extensions
of MIP. When introducing new functions which may add to the
complicity, existing solutions are more vulnerable to break.
Mobile IP, which has primarily been deployed in a centralized manner
for the hierarchical mobile networks, already has numerous variants
and extensions including PMIP, Fast MIP (FMIP) [RFC4068] [RFC4988] ,
Proxy-based FMIP (PFMIP) [RFC5949] , hierarchical MIP (HMIP)
[RFC5380] , Dual-Stack Mobile IP (DSMIP) [RFC5454] [RFC5555] and
there may be more to come. These different modifications or
extensions of MIP have been developed over the years owing to the
different needs that are found afterwards. Deployment can then
become complicated, especially when interoperability with different
deployments is an issue.
A desirable feature of mobility management is to be able to work with
network architectures of both hierarchical networks and flattened
networks, so that the mobility management protocol possesses enough
flexibility 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 mobility signaling. Such
flexibility in the design is compatible with the goal to integrate
different mobility variants as options. Some additional extensions
to the base protocols may then be needed to improve the integration
while avoiding existing functions to break.
5. Requirements
After reviewing the problems and limitations of centralized
deployment in Section 4, this section states the requirements as
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follows:
5.1. Distributed deployment
REQ1: Distributed deployment
IP mobility, network access and routing solutions provided by
DMM SHALL enable a distributed deployment of mobility
management of IP sessions so that the traffic can be routed in
an optimal manner without traversing centrally deployed
mobility anchors.
Motivation: The motivations of this requirement are to match
mobility deployment with current trend in network evolution:
more cost and resource effective to cache and distribute
contents when combining distributed anchors with caching
systems (e.g., CDN); improve scalability; avoid single point
of failure; mitigate threats being focused on a centrally
deployed anchor, e.g., home agent and local mobility anchor.
This requirement addresses the problems PS1, PS2, PS3, and PS4
explained in Section 4 above.
5.2. Transparency to Upper Layers when needed
REQ2: Transparency to Upper Layers when needed
The DMM solutions SHALL provide transparency above the IP
layer when needed. Such transparency is needed, when the
mobile hosts or entire mobile networks change their point of
attachment to the Internet, for the application flows that
cannot cope with a change of IP address. Otherwise the
support to maintain a stable home IP address or prefix during
handover may be declined.
Motivation: The motivation of this requirement is to enable
more efficient use of network resources and more efficient
routing by not maintaining a stable IP home IP address when
there is no such need.
This requirement addresses the problems PS5 as well as the other
related problem O-PS1 which are explained in Section 4 above.
5.3. IPv6 deployment
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REQ3: IPv6 deployment
The DMM solutions SHOULD target IPv6 as primary deployment and
SHOULD NOT be tailored specifically to support IPv4, in
particular in situations where private IPv4 addresses and/or
NATs are used.
Motivation: The motivation for this requirement is to be
inline with the general orientation of IETF. Moreover, DMM
deployment is foreseen in mid-term/long-term, hopefully in an
IPv6 world. It is also unnecessarily complex to solve this
problem for IPv4, as we will not be able to use some of the
IPv6-specific features/tools.
5.4. Compatibility
REQ4: Compatibility
The DMM solution SHOULD be able to work between trusted
administrative domains when allowed by the security measures
deployed between these domains. Furthermore, the DMM solution
SHOULD preserve backwards compatibility with existing network
deployment and end hosts. For example, depending on the
environment in which dmm is deployed, the dmm solutions may
need to be compatible with other existing mobility protocols
that are deployed in that environment or may need to be
interoperable with the network or the mobile hosts/routers
that do not support the dmm enabling protocol.
Motivation: The motivation of this requirement is to allow
inter-domain operation if desired and to preserve backwards
compatibility so that the existing networks and hosts are not
affected and do not break.
5.5. Existing mobility protocols
REQ5: Existing mobility protocols
A DMM solution SHOULD first consider reusing and extending the
existing mobility protocols before specifying new protocols.
Motivation: The purpose is to reuse the existing protocols
first before considering new protocols.
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5.6. Security considerations
REQ6: Security considerations
The protocol solutions for DMM SHALL consider security, for
example authentication and authorization mechanisms that allow
a legitimate mobile host/router to access to the DMM service,
protection of signaling messages of the protocol solutions in
terms of authentication, data integrity, and data
confidentiality, opti-in or opt-out data confidentiality to
signaling messages depending on network environments or user
requirements.
Motivation and problem statement: Mutual authentication and
authorization between a mobile host/router and an access
router providing the DMM service to the mobile host/router are
required to prevent potential attacks in the access network of
the DMM service. Otherwise, various attacks such as
impersonation, denial of service, man-in-the-middle attacks,
etc. are present to obtain illegitimate access or to collapse
the DMM service.
Signaling messages are subject to various attacks since these
messages carry context of a mobile host/router. For instance,
a malicious node can forge and send a number of signaling
messages to redirect traffic to a specific node.
Consequently, the specific node is under a denial of service
attack, whereas other nodes are not receiving their traffic.
As signaling messages travel over the Internet, the end-to-end
security is required.
6. Security Considerations
Distributed mobility management (DMM) requires two kinds of security
considerations: 1) access network security that only allows a
legitimate mobile host/router to access the DMM service; 2) end-to-
end security that protects signaling messages for the DMM service.
Access network security is required between the mobile host/router
and the access network providing the DMM service. End-to-end
security is required between nodes that participate in the DMM
protocol.
It is necessary to provide sufficient defense against possible
security attacks, or to adopt existing security mechanisms and
protocols to provide sufficient security protections. For instance,
EAP based authentication can be used for access network security,
while IPsec can be used for end-to-end security.
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7. IANA Considerations
None
8. Co-authors and Contributors
This problem statement document is a joint effort among the following
participants. Each individual has made significant contributions to
this work.
Dapeng Liu: liudapeng@chinamobile.com
Pierrick Seite: pierrick.seite@orange-ftgroup.com
Hidetoshi Yokota: yokota@kddilabs.jp
Charles E. Perkins: charliep@computer.org
Melia Telemaco: telemaco.melia@alcatel-lucent.com
Elena Demaria: elena.demaria@telecomitalia.it
Peter McCann: Peter.McCann@huawei.com
Wassim Michel Haddad: Wassam.Haddad@ericsson.com
Hui Deng: denghui@chinamobile.com
Tricci So: tso@zteusa.com
Jong-Hyouk Lee: jh.lee@telecom-bretagne.eu
Seok Joo Koh: sjkoh@knu.ac.kr
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[I-D.ietf-netext-pd-pmip]
Zhou, X., Korhonen, J., Williams, C., Gundavelli, S., and
C. Bernardos, "Prefix Delegation for Proxy Mobile IPv6",
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draft-ietf-netext-pd-pmip-02 (work in progress),
March 2012.
[I-D.jikim-dmm-pmip]
Kim, J., Koh, S., Jung, H., and Y. Han, "Use of Proxy
Mobile IPv6 for Distributed Mobility Control",
draft-jikim-dmm-pmip-00 (work in progress), March 2012.
[I-D.yokota-dmm-scenario]
Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case
scenarios for Distributed Mobility Management",
draft-yokota-dmm-scenario-00 (work in progress),
October 2010.
[Paper-Distributed.Centralized.Mobility]
Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed
or Centralized Mobility", Proceedings of Global
Communications Conference (GlobeCom), December 2009.
[Paper-Distributed.Dynamic.Mobility]
Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed
Dynamic Mobility Management Scheme Designed for Flat IP
Architectures", Proceedings of 3rd International
Conference on New Technologies, Mobility and Security
(NTMS), 2008.
[Paper-Distributed.Mobility.PMIP]
Chan, H., "Proxy Mobile IP with Distributed Mobility
Anchors", Proceedings of GlobeCom Workshop on Seamless
Wireless Mobility, December 2010.
[Paper-Distributed.Mobility.Review]
Chan, H., Yokota, H., Xie, J., Seite, P., and D. Liu,
"Distributed and Dynamic Mobility Management in Mobile
Internet: Current Approaches and Issues, Journal of
Communications, vol. 6, no. 1, pp. 4-15, Feb 2011.",
Proceedings of GlobeCom Workshop on Seamless Wireless
Mobility, February 2011.
[Paper-Distributed.Mobility.SAE]
Fisher, M., Anderson, F., Kopsel, A., Schafer, G., and M.
Schlager, "A Distributed IP Mobility Approach for 3G SAE",
Proceedings of the 19th International Symposium on
Personal, Indoor and Mobile Radio Communications (PIMRC),
2008.
[Paper-Locating.User]
Kirby, G., "Locating the User", Communication
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International, 1995.
[Paper-Migrating.Home.Agents]
Wakikawa, R., Valadon, G., and J. Murai, "Migrating Home
Agents Towards Internet-scale Mobility Deployments",
Proceedings of the ACM 2nd CoNEXT Conference on Future
Networking Technologies, December 2006.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
[RFC4068] Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068,
July 2005.
[RFC4988] Koodli, R. and C. Perkins, "Mobile IPv4 Fast Handovers",
RFC 4988, October 2007.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5380] Soliman, H., Castelluccia, C., ElMalki, K., and L.
Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility
Management", RFC 5380, October 2008.
[RFC5454] Tsirtsis, G., Park, V., and H. Soliman, "Dual-Stack Mobile
IPv4", RFC 5454, March 2009.
[RFC5555] Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
Routers", RFC 5555, June 2009.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.
[RFC5949] Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F.
Xia, "Fast Handovers for Proxy Mobile IPv6", RFC 5949,
September 2010.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
Author's Address
H Anthony Chan (editor)
Huawei Technologies
5340 Legacy Dr. Building 3, Plano, TX 75024, USA
Email: h.a.chan@ieee.org
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-
Dapeng Liu
China Mobile
Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China
Email: liudapeng@chinamobile.com
-
Pierrick Seite
France Telecom - Orange
4, rue du Clos Courtel, BP 91226, Cesson-Sevigne 35512, France
Email: pierrick.seite@orange-ftgroup.com
-
Hidetoshi Yokota
KDDI Lab
2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan
Email: yokota@kddilabs.jp
-
Charles E. Perkins
Huawei Technologies
Email: charliep@computer.org
-
Jouni Korhonen
Nokia Siemens Networks
Email: jouni.korhonen@nsn.com
-
Melia Telemaco
Alcatel-Lucent Bell Labs
Email: telemaco.melia@alcatel-lucent.com
-
Elena Demaria
Telecom Italia
via G. Reiss Romoli, 274, TORINO, 10148, Italy
Email: elena.demaria@telecomitalia.it
-
Jong-Hyouk Lee
RSM Department, Telecom Bretagne
Cesson-Sevigne, 35512, France
Email: jh.lee@telecom-bretagne.eu
-
Tricci So
ZTE
Email: tso@zteusa.com
-
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30, Leganes, Madrid 28911, Spain
Email: cjbc@it.uc3m.es
-
Peter McCann
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Huawei Technologies
Email: PeterMcCann@huawei.com
-
Seok Joo Koh
Kyungpook National University, Korea
Email: sjkoh@knu.ac.kr
-
Wen Luo
ZTE
No.68, Zijinhua RD,Yuhuatai District, Nanjing, Jiangsu 210012, China
Email: luo.wen@zte.com.cn
-
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