draft-ietf-dmm-requirements-03.txt   draft-ietf-dmm-requirements-04.txt 
Network Working Group H. Chan (Ed.) Network Working Group H. Chan (Ed.)
Internet-Draft Huawei Technologies (more Internet-Draft Huawei Technologies (more
Intended status: Informational co-authors on P. 17) Intended status: Informational co-authors on P. 17)
Expires: June 25, 2013 D. Liu Expires: November 9, 2013 D. Liu
China Mobile China Mobile
P. Seite P. Seite
France Telecom - Orange France Telecom - Orange
H. Yokota H. Yokota
KDDI Lab KDDI Lab
J. Korhonen J. Korhonen
Nokia Siemens Networks Nokia Siemens Networks
December 22, 2012 May 8, 2013
Requirements for Distributed Mobility Management Requirements for Distributed Mobility Management
draft-ietf-dmm-requirements-03 draft-ietf-dmm-requirements-04
Abstract Abstract
This document defines the requirements for Distributed Mobility This document defines the requirements for Distributed Mobility
Management (DMM) in IPv6 deployments. The traditionally hierarchical Management (DMM) in IPv6 deployments. The hierarchical structure in
structure of cellular networks has led to deployment models which are traditional wireless networks has led to deployment models which are
in practice centralized. Mobility management with logically in practice centralized. Mobility management with logically
centralized mobility anchoring in current mobile networks is prone to centralized mobility anchoring in current mobile networks is prone to
suboptimal routing and raises scalability issues. Such centralized suboptimal routing and raises scalability issues. Such centralized
functions can lead to single points of failure and inevitably functions can lead to single points of failure and inevitably
introduce longer delays and higher signaling loads for network introduce longer delays and higher signaling loads for network
operations related to mobility management. The objective is to operations related to mobility management. The objective is to
enhance mobility management in order to meet the primary goals in enhance mobility management in order to meet the primary goals in
network evolution, i.e., improve scalability, avoid single points of network evolution, i.e., improve scalability, avoid single points of
failure, enable transparent mobility support to upper layers only failure, enable transparent mobility support to upper layers only
when needed, and so on. Distributed mobility management must be when needed, and so on. Distributed mobility management must be
secure and compatible with existing network deployments and end secure and may co-exist with existing network deployments and end
hosts. hosts.
Requirements Language
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 [RFC2119].
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions used in this document . . . . . . . . . . . . . . 6 2. Conventions used in this document . . . . . . . . . . . . . . 6
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
3. Centralized versus distributed mobility management . . . . . . 6 3. Centralized versus distributed mobility management . . . . . . 7
3.1. Centralized mobility management . . . . . . . . . . . . . 7 3.1. Centralized mobility management . . . . . . . . . . . . . 7
3.2. Distributed mobility management . . . . . . . . . . . . . 8 3.2. Distributed mobility management . . . . . . . . . . . . . 8
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9 4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Distributed deployment . . . . . . . . . . . . . . . . . . 9 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Transparency to Upper Layers when needed . . . . . . . . . 10 5.1. Distributed deployment . . . . . . . . . . . . . . . . . . 11
4.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 11 5.2. Transparency to Upper Layers when needed . . . . . . . . . 11
4.4. Existing mobility protocols . . . . . . . . . . . . . . . 11 5.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 12
4.5. Co-existence . . . . . . . . . . . . . . . . . . . . . . . 11 5.4. Existing mobility protocols . . . . . . . . . . . . . . . 12
4.6. Security considerations . . . . . . . . . . . . . . . . . 12 5.5. Co-existence . . . . . . . . . . . . . . . . . . . . . . . 12
4.7. Flexible multicast distribution . . . . . . . . . . . . . 13 5.6. Security considerations . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13 5.7. Multicast considerations . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Co-authors and Contributors . . . . . . . . . . . . . . . . . 14 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8. Co-authors and Contributors . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
In the past decade a fair number of mobility protocols have been In the past decade a fair number of mobility protocols have been
standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301] [RFC5213]. standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301] [RFC5213].
Although the protocols differ in terms of functions and associated Although the protocols differ in terms of functions and associated
message formats, we can identify a few key common features: message formats, we can identify a few key common features:
a centralized mobility anchor providing global reachability and an o a centralized mobility anchor providing global reachability and an
always-on experience to the user; always-on experience to the user;
extensions to the base protocols to optimize handover performance o extensions to the base protocols to optimize handover performance
while users roam across wireless cells; and while users roam across wireless cells; and
extensions to enable the use of heterogeneous wireless interfaces o extensions to enable the use of heterogeneous wireless interfaces
for multi-mode terminals (e.g. smartphones). for multi-mode terminals (e.g. smartphones).
The presence of the centralized mobility anchor allows a mobile node The presence of the centralized mobility anchor allows a mobile node
to remain reachable when it is not connected to its home domain. The to remain reachable after it has moved to a different network. The
anchor point, among other tasks, ensures connectivity by forwarding anchor point, among other tasks, ensures connectivity by forwarding
packets destined to, or sent from, the mobile node. In practice, packets destined to, or sent from, the mobile node. In practice,
most of the deployed architectures today have a small number of most of the deployed architectures today have a small number of
centralized anchors managing the traffic of millions of mobile nodes. centralized anchors managing the traffic of millions of mobile nodes.
Compared with a distributed approach, a centralized approach is Compared with a distributed approach, a centralized approach is
likely to have several issues or limitations affecting performance likely to have several issues or limitations affecting performance
and scalability, which require costly network dimensioning and and scalability, which require costly network dimensioning and
engineering to resolve. engineering to resolve.
To optimize handovers from the perspective of mobile nodes, the base To optimize handovers from the perspective of mobile nodes, the base
protocols have been extended to efficiently handle packet forwarding protocols have been extended to efficiently handle packet forwarding
between the previous and new points of attachment. These extensions between the previous and new points of attachment. These extensions
are necessary when applications have stringent requirements in terms are necessary when applications have stringent requirements in terms
of delay. Notions of localization and distribution of local agents of delay. Notions of localization and distribution of local agents
have been introduced to reduce signaling overhead [Paper- have been introduced to reduce signaling overhead [Paper-
Distributed.Centralized.Mobility]. Unfortunately, today we witness Distributed.Centralized.Mobility]. Unfortunately, today we witness
difficulties in getting such protocols deployed, resulting in sub- difficulties in getting such protocols deployed, resulting in sub-
optimal choices for the network operators. optimal choices for the network operators.
Moreover, the availability of multi-mode devices and the possibility Moreover, the availability of multiple-interface host and the
of using several network interfaces simultaneously have motivated the possibility of using several network interfaces simultaneously have
development of even more protocol extensions to add more capabilities motivated the development of even more protocol extensions to add
and to combine IP multicasting to the base protocol. In the end, more capabilities to the mobility management protocol. In the end,
deployment is further complicated with the multitude of extensions. deployment is further complicated with the multitude of extensions.
As an effective transport method for multimedia data delivery, IP
multicast support, including optimizations, have been introduced but
by "patching-up" procedure after completing the design of reference
mobility protocol, leading to network inefficiency and non-optimal
routing.
Mobile users are, more than ever, consuming Internet content; such Mobile users are, more than ever, consuming Internet content; such
traffic imposes new requirements on mobile core networks for data traffic imposes new requirements on mobile core networks for data
traffic delivery. The presence of content providers closer to the traffic delivery. The presence of content providers closer to
mobile/fixed Internet Service Providers network requires taking into Internet Service Providers (ISP) network requires taking into account
account local Content Delivery Networks (CDNs) while providing local Content Delivery Networks (CDNs) while providing mobility
mobility services. Moreover, when the traffic demand exceeds services. Moreover, when the traffic demand exceeds available
available capacity, service providers need to implement new capacity, service providers need to implement new strategies such as
strategies such as selective traffic offload (e.g. 3GPP work items selective traffic offload (e.g. 3GPP work items LIPA/SIPTO
LIPA/SIPTO [TS.23829]) through alternative access networks (e.g. [TS.23.401]) through alternative access networks (e.g. WLAN) [Paper-
WLAN) [Paper-Mobile.Data.Offloading]. Gateway selection mechanism is Mobile.Data.Offloading]. A gateway selection mechanism also takes
also taking the user proximity into account within EPC [TS.29303]. the user proximity into account within EPC [TS.29303]. These
These mechanisms were not pursued in the past owing to charging and mechanisms were not pursued in the past owing to charging and billing
billing reasons. However assigning a gateway anchor node from a reasons. Assigning a gateway anchor node from a visited network in
visited network in roaming scenario has until recently been done and roaming scenario has until recently been done and are limited to
are limited to voice services only. Issues such as charging and voice services only. Charging and billing require solutions beyond
billing require solutions beyond the mobility protocol. the mobility protocol.
When demand exceeds capacity, both traffic offloading and CDN Both traffic offloading and CDN mechanisms could benefit from the
mechanisms could benefit from the development of mobile architectures development of mobile architectures with fewer levels of routing
with fewer levels of routing hierarchy introduced into the data path hierarchy introduced into the data path by the mobility management
by the mobility management system. This trend towards so-called system. This trend towards so-called "flat networks" is reinforced
"flat networks" is reinforced by a shift in user traffic behavior. by a shift in user traffic behavior. In particular, there are direct
In particular, there is an increase in direct communications among communications among peers in the same geographical area.
peers in the same geographical area. Distributed mobility management Distributed mobility management in a truly flat mobile architecture
in a truly flat mobile architecture would anchor the traffic closer would anchor the traffic closer to the point of attachment of the
to the point of attachment of the user, overcoming the suboptimal user.
route stretch of a centralized mobility scheme.
While deploying today's mobile networks, service providers face new Today's mobile networks present service providers with new
challenges. Mobility patterns indicate that, more often than not, challenges. Mobility patterns indicate that mobile nodes remain
mobile nodes remain attached to the same point of attachment for attached to the same point of attachment for considerable periods of
considerable periods of time [Paper-Locating.User] . Therefore it is time [Paper-Locating.User]. Specific IP mobility management support
not uncommon to observe that specific IP mobility management support
is not required for applications that launch and complete their is not required for applications that launch and complete their
sessions while the mobile node is connected to the same point of sessions while the mobile node is connected to the same point of
attachment. However, currently, IP mobility support is designed for attachment. However, currently, IP mobility support is designed for
always-on operation, maintaining all parameters of the context for always-on operation, maintaining all parameters of the context for
each mobile subscriber for as long as they are connected to the each mobile subscriber for as long as they are connected to the
network. This can result in a waste of resources and ever-increasing network. This can result in a waste of resources and unnecessary
costs for the service provider. Infrequent node mobility coupled costs for the service provider. Infrequent node mobility coupled
with application intelligence suggest that mobility can be provided with application intelligence suggest that mobility support could be
selectively, thus simplifying the context maintained in the different provided selectively, thus reducing the amount of context maintained
nodes of the mobile network. in the network.
The DMM charter addresses two complementary aspects of mobility The distributed mobility managemetn (DMM) charter addresses two
management procedures: the distribution of mobility anchors towards a complementary aspects of mobility management procedures: the
more flat network and the dynamic activation/deactivation of mobility distribution of mobility anchors towards a more flat network and the
protocol support as an enabler to distributed mobility management. dynamic activation/deactivation of mobility protocol support as an
The former aims at positioning mobility anchors (HA, LMA) closer to enabler to distributed mobility management. The former aims at
the user; ideally, mobility agents could be collocated with the positioning mobility anchors (e.g., HA, LMA) closer to the user;
first-hop router. The latter, facilitated by the distribution of ideally, mobility agents could be collocated with the first-hop
mobility anchors, aims at identifying when mobility support must be router. The latter, facilitated by the distribution of mobility
activated and identifying sessions that do not require mobility anchors, aims at identifying when mobility support must be activated
management support -- thus reducing the amount of state information and identifying sessions that do not require mobility management
that must be maintained in various mobility agents of the mobile support -- thus reducing the amount of state information that must be
network. The key idea is that dynamic mobility management relaxes maintained in various mobility agents of the mobile network. The key
some of the constraints of previously-standardized mobility idea is that dynamic mobility management relaxes some of the
management solutions and, by doing so, it can avoid the establishment constraints of previously-standardized mobility management solutions
of non-optimal tunnels between two topologically distant anchors. and, by doing so, it can avoid the unnecessary establishment of
mechanisms to forward traffic from an old to a new mobility anchor.
Given this motivational background in this section, this document This document compares distributed mobility management with
compares distributed mobility management with centralized mobility centralized mobility management in Section 3. The problems that can
management in Section 3. The requirements to address these problems be addressed with DMM are summarized in Section 4. The requirements
are given in Section 4. Finally, security considerations are to address various problems are given in Section 5. Finally,
discussed in Section 5. security considerations are discussed in Section 6.
The problem statement and the use cases [I-D.yokota-dmm-scenario] can The problem statement and the use cases [I-D.yokota-dmm-scenario] can
be found in [Paper-Distributed.Mobility.Review]. be found in [Paper-Distributed.Mobility.Review].
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
skipping to change at page 7, line 24 skipping to change at page 7, line 31
continuously delivered to a mobile node at its home address, then all continuously delivered to a mobile node at its home address, then all
sessions using that home address are unaffected even though the sessions using that home address are unaffected even though the
routing address (CoA) changes. routing address (CoA) changes.
The next two subsections explain centralized and distributed mobility The next two subsections explain centralized and distributed mobility
management functions in the network. management functions in the network.
3.1. Centralized mobility management 3.1. Centralized mobility management
In centralized mobility management, the mapping information between In centralized mobility management, the mapping information between
the persistent node identifier and the changing IP address of a the persistent node identifier and the locator IP address of a mobile
mobile node (MN) is kept at a single mobility anchor. At the same node (MN) is kept at a single mobility anchor. At the same time,
time, packets destined to the MN are routed via this anchor. In packets destined to the MN are routed via this anchor. In other
other words, such mobility management systems are centralized in both words, such mobility management systems are centralized in both the
the control plane and the data plane. control plane and the data plane.
Many existing mobility management deployments make use of centralized Many existing mobility management deployments make use of centralized
mobility anchoring in a hierarchical network architecture, as shown mobility anchoring in a hierarchical network architecture, as shown
in Figure 1. Examples of such centralized mobility anchors are the in Figure 1. Examples of such centralized mobility anchors are the
home agent (HA) and local mobility anchor (LMA) in Mobile IPv6 home agent (HA) and local mobility anchor (LMA) in Mobile IPv6
[RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively. Current [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively. Current
cellular networks such as the Third Generation Partnership Project cellular networks such as the Third Generation Partnership Project
(3GPP) UMTS networks, CDMA networks, and 3GPP Evolved Packet System (3GPP) GPRS networks, CDMA networks, and 3GPP Evolved Packet System
(EPS) networks employ centralized mobility management too. In (EPS) networks employ centralized mobility management too. In
particular, Gateway GPRS Support Node (GGSN) and Serving GPRS Support particular, the Gateway GPRS Support Node (GGSN), Serving GPRS
Node (SGSN) in the 3GPP UMTS hierarchical network, and the Packet Support Node (SGSN) and Radio Network Controller (RNC) in the 3GPP
data network Gateway (P-GW) and Serving Gateway (S-GW) in the 3GPP GPRS hierarchical network, and the Packet Data Network Gateway (P-GW)
EPS network, respectively, act as anchors in a hierarchy. and Serving Gateway (S-GW) in the 3GPP EPS network, respectively, act
as anchors in a hierarchy.
UMTS 3GPP SAE MIP/PMIP 3G GPRS 3GPP EPS MIP/PMIP
+------+ +------+ +------+ +------+ +------+ +------+
| GGSN | | P-GW | |HA/LMA| | GGSN | | P-GW | |HA/LMA|
+------+ +------+ +------+ +------+ +------+ +------+
/\ /\ /\ /\ /\ /\
/ \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \
+------+ +------+ +------+ +------+ +------+ +------+ / \ / \ / \
| SGSN | | SGSN | | S-GW | | S-GW | |MN/MAG| |MN/MAG| / \ / \ / \
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| SGSN | | SGSN | | S-GW | | S-GW | |MN/MAG| |MN/MAG|
+------+ +------+ +------+ +------+ +------+ +------+
/\ /\
/ \ / \
/ \ / \
+---+ +---+ +---+ +---+
|RNC| |RNC| |RNC| |RNC|
+---+ +---+ +---+ +---+
Figure 1. Centralized mobility management. Figure 1. Centralized mobility management.
3.2. Distributed mobility management 3.2. Distributed mobility management
Mobility management functions may also be distributed to multiple 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 as shown in Figure 2, so that a mobile node in any of these
networks may be served by a closeby mobility function (MF). networks may be served by a nearby mobility function (MF).
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| MF | | MF | | MF | | MF | | MF | | MF | | MF | | MF |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| |
---- +----+
| MN | | MN |
---- +----+
Figure 2. Distributed mobility management. Figure 2. Distributed mobility management.
Mobility management may be partially or fully distributed. In the Mobility management may be partially or fully distributed. In the
former case only the data plane is distributed. Fully distributed former case only the data plane is distributed. Fully distributed
mobility management implies that both the data plane and the control mobility management implies that both the data plane and the control
plane are distributed. These different approaches are described in plane are distributed. Such concepts of data and control plane
detail in [I-D.yokota-dmm-scenario]. While mobility management can separation are not yet described in the IETF developed mobility
be distributed, it is not necessary for other functions such as protocols so far but are described in detail in [I-D.yokota-dmm-
subscription management, subscription database, and network access scenario]. While mobility management can be distributed, it is not
authentication to be similarly distributed. necessary for other functions such as subscription management,
subscription database, and network access authentication to be
similarly distributed.
A distributed mobility management scheme for future flat IP-based A distributed mobility management scheme for flat IP-based mobile
mobile network architecture consisting of access nodes is proposed in network architecture consisting of access nodes is proposed in
[Paper-Distributed.Dynamic.Mobility]. Its benefits over centralized [Paper-Distributed.Dynamic.Mobility]. Its benefits over centralized
mobility management are shown through simulations in [Paper- mobility management are shown through simulations in [Paper-
Distributed.Centralized.Mobility]. Moreover, the (re)use and Distributed.Centralized.Mobility]. Moreover, the (re)use and
extension of existing protocols in the design of both fully extension of existing protocols in the design of both fully
distributed mobility management [Paper-Migrating.Home.Agents] [Paper- distributed mobility management [Paper-Migrating.Home.Agents] [Paper-
Distributed.Mobility.SAE] and partially distributed mobility Distributed.Mobility.SAE] and partially distributed mobility
management [Paper-Distributed.Mobility.PMIP] [Paper- management [Paper-Distributed.Mobility.PMIP] [Paper-
Distributed.Mobility.MIP] have been reported in the literature. Distributed.Mobility.MIP] have been reported in the literature.
Therefore, before designing new mobility management protocols for a Therefore, before designing new mobility management protocols for a
future flat IP architecture, it is recommended to first consider future flat IP architecture, it is recommended to first consider
whether existing mobility management protocols can be extended to whether existing mobility management protocols can be extended to
serve a flat IP architecture. serve a flat IP architecture.
4. Requirements 4. Problem Statement
After comparing distributed mobility management against centralized
deployment in Section 3, this section states the requirements as
follows:
4.1. Distributed deployment
REQ1: Distributed deployment
IP mobility, network access and routing solutions provided by
DMM MUST enable distributed deployment for mobility management
of IP sessions so that traffic does not need to traverse
centrally deployed mobility anchors and thus can be routed in
an optimal manner.
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.
This requirement addresses problems PS1, PS2, PS3, and PS4 in the The problems that can be addressed with DMM are summarized in the
following. following:
PS1: Non-optimal routes PS1: Non-optimal routes
Routing via a centralized anchor often results in a longer Routing via a centralized anchor often results in a longer
route. The problem is manifested, for example, when accessing route. The problem is manifested, for example, when accessing
a local server or servers of a Content Delivery Network (CDN), a local server or servers of a Content Delivery Network (CDN),
or when receiving locally available IP multicast or sending IP or when receiving locally available IP multicast or sending IP
multicast packets. multicast packets.
PS2: Divergence from other evolutionary trends in network PS2: Divergence from other evolutionary trends in network
architectures such as distribution of content delivery. architectures such as distribution of content delivery.
Centralized mobility management can become non-optimal with a Centralized mobility management can become non-optimal with a
flat network architecture. flat network architecture.
PS3: Low scalability of centralized tunnel management and mobility PS3: Low scalability of centralized tunnel management and mobility
context maintenance context maintenance
Setting up tunnels through a central anchor and maintaining Setting up tunnels through a central anchor and maintaining
mobility context for each MN therein requires more resources in mobility context for each MN requires more resources in a
a centralized design, thus reducing scalability. Distributing centralized design, thus reducing scalability. Distributing
the tunnel maintenance function and the mobility context the tunnel maintenance function and the mobility context
maintenance function among different network entities can maintenance function among different network entities with
increase scalability. proper signaling protocol design can increase scalability.
PS4: Single point of failure and attack PS4: Single point of failure and attack
Centralized anchoring may be more vulnerable to single points Centralized anchoring designs may be more vulnerable to single
of failures and attacks than a distributed system. The impact points of failures and attacks than a distributed system. The
of a successful attack on a system with centralized mobility impact of a successful attack on a system with centralized
management can be far greater as well. mobility management can be far greater as well.
4.2. Transparency to Upper Layers when needed PS5: Unnecessarily reserving resources to provide mobility support
to nodes that do not need such support
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."
PS6: (Related problem) Mobility signaling overhead with peer-to-peer
communication
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. In such a case, it is better to enable
mobility support selectively.
PS7: (Related problem) Complicated deployment with many MIP variants
and extensions
Deployment is complicated with many variants and extensions of
MIP. When introducing new functions which may add to the
complexity, existing solutions are more vulnerable to break.
PS8: Duplicate multicast traffic
IP multicast distribution over architectures using IP mobility
solutions (e.g. 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.
5. Requirements
After comparing distributed mobility management against centralized
deployment in Section 3, this section identifies the following
requirements:
5.1. Distributed deployment
REQ1: Distributed deployment
IP mobility, network access and routing solutions provided by
DMM MUST enable distributed deployment for mobility management
of some flows so that traffic does not need to traverse
centrally deployed mobility anchors and thus can be routed in
an optimal manner.
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.
This requirement addresses problems PS1, PS2, PS3, and PS4 in Section
4.
5.2. Transparency to Upper Layers when needed
REQ2: Transparency to Upper Layers when needed REQ2: Transparency to Upper Layers when needed
DMM solutions MUST provide transparent mobility support above DMM solutions MUST provide transparent mobility support above
the IP layer when needed. Such transparency is needed, for the IP layer when needed. Such transparency is needed, for
example, when, upon change of point of attachment to the example, when, upon change of point of attachment to the
Internet, an application flow cannot cope with a change in the network, an application flow cannot cope with a change in the
IP address. However, it is not always necessary to maintain a IP address. However, it is not always necessary to maintain a
stable home IP address or prefix for every application or at stable home IP address or prefix for every application or at
all times for a mobile node. all times for a mobile node.
Motivation: The motivation of this requirement is to enable Motivation: The motivation of this requirement is to enable
more efficient use of network resources and more efficient more efficient use of network resources and more efficient
routing by not maintaining context at the mobility anchor when routing by not maintaining context at the mobility anchor when
there is no such need. there is no such need.
This requirement addresses the problem PS5 as well as the related This requirement addresses the problem PS5 as well as the related
problem PS6. problem PS6 in Section 4.
PS5: Wasting resources to provide mobility support to nodes that do
not need such support
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 IP session continuity. Sometimes, the
entire application session runs while the terminal does not
change the point of attachment.
PS6: (Related problem) Mobility signaling overhead with peer-to-peer
communication
Wasting resources when mobility signaling (e.g., maintenance of
the tunnel, keep alive, 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 alives, etc.) wastes network resources for no application
gain. In such a case, it is better to enable mobility support
selectively.
4.3. IPv6 deployment 5.3. IPv6 deployment
REQ3: IPv6 deployment REQ3: IPv6 deployment
DMM solutions SHOULD target IPv6 as the primary deployment DMM solutions SHOULD target IPv6 as the primary deployment
environment and SHOULD NOT be tailored specifically to support environment and SHOULD NOT be tailored specifically to support
IPv4, in particular in situations where private IPv4 addresses IPv4, in particular in situations where private IPv4 addresses
and/or NATs are used. and/or NATs are used.
Motivation: This requirement is to be inline with the general Motivation: This requirement conforms to the general
orientation of IETF work. DMM deployment is foreseen in mid- orientation of IETF work. DMM deployment is foreseen in mid-
to long-term horizon, when IPv6 is expected to be far more to long-term horizon, when IPv6 is expected to be far more
common than today. It is also unnecessarily complex to solve common than today. It is also unnecessarily complex to solve
this problem for IPv4, as we will not be able to use some of this problem for IPv4, as we will not be able to use some of
the IPv6-specific features/tools. the IPv6-specific features/tools.
4.4. Existing mobility protocols 5.4. Existing mobility protocols
REQ4: Existing mobility protocols REQ4: Existing mobility protocols
A DMM solution SHOULD first consider reusing and extending A DMM solution SHOULD first consider reusing and extending
IETF-standardized protocols before specifying new protocols. IETF-standardized protocols before specifying new protocols.
4.5. Co-existence 5.5. Co-existence
REQ5: Co-existence with deployed networks and hosts REQ5: Co-existence with deployed networks and hosts
The DMM solution MUST be able to co-exist with existing The DMM solution MUST be able to co-exist with existing
network deployments and end hosts. For example, depending on network deployments and end hosts. For example, depending on
the environment in which DMM is deployed, DMM solutions may the environment in which DMM is deployed, DMM solutions may
need to be compatible with other deployed mobility protocols need to be compatible with other deployed mobility protocols
or may need to interoperate with a network or mobile hosts/ or may need to co-exist with a network or mobile hosts/routers
routers that do not support DMM protocols. Furthermore, a DMM that do not support DMM protocols. The mobile node may also
solution SHOULD work across different networks, possibly move between different access networks, where some of them may
operated as separate administrative domains, when allowed by neither support DMM nor another mobility protocol.
the trust relationship between them. Furthermore, a DMM solution SHOULD work across different
networks, possibly operated as separate administrative
Motivation: The motivations of this requirement are (1) to domains, when allowed by the trust relationship between them.
preserve backwards compatibility so that existing networks and
hosts are not affected and continue to function as usual, and
(2) enable inter-domain operation if desired.
This requirement addresses the following related problem PS7.
PS7: (Related problem) Complicated deployment with too many MIP Motivation: (a) to preserve backwards compatibility so that
variants and extensions existing networks and hosts are not affected and continue to
function as usual, and (b) enable inter-domain operation if
desired.
Deployment is complicated with many variants and extensions of This requirement addresses the following related problem PS7 in
MIP. When introducing new functions which may add to the Section 4.
complexity, existing solutions are more vulnerable to break.
4.6. Security considerations 5.6. Security considerations
REQ6: Security considerations REQ6: Security considerations
DMM protocol solutions MUST consider security aspects, DMM protocol solutions MUST consider security risks introduced
including confidentiality and integrity. Examples of aspects by DMM into the network. Examples of such risks to be
to be considered are authentication and authorization considered are authentication and authorization mechanisms
mechanisms that allow a legitimate mobile host/router to use that allow a legitimate mobile host/router to use the mobility
the mobility support provided by the DMM solution; signaling support provided by the DMM solution; redirecting traffic to
message protection in terms of authentication, encryption, the wrong host when providing DMM support; signaling message
etc.; data integrity and confidentiality; opt-in or opt-out protection in terms of authentication, encryption, data
data confidentiality to signaling messages depending on integrity and confidentiality.
network environments or user requirements.
Motivation: Mutual authentication and authorization between a Motivation: Various attacks such as impersonation, denial of
mobile host/router and an access router providing the DMM service, man-in-the-middle attacks, and so on, can be mounted
service to the mobile host/router are required to prevent against a DMM network and need to be protected against. Proof
potential attacks in the access network of the DMM service. of possession of past and new IP addresses may be needed.
Various attacks such as impersonation, denial of service, man-
in-the-middle attacks, and so on, can be mounted against a DMM
service and need to be protected against.
Signaling messages can be subject to various attacks since Signaling messages can be subject to various attacks since
they carry critical context information about a mobile node/ they carry critical context information about a mobile node/
router. For instance, a malicious node can forge a number of router. For instance, a malicious node can forge a number of
signaling messages thus redirecting traffic from its signaling messages thus redirecting traffic from its
legitimate path. Consequently, the specific node is under a legitimate path. Consequently, the specific node is under a
denial of service attack, whereas other nodes do not receive denial of service attack, whereas other nodes do not receive
their traffic. As signaling messages may travel over the their traffic. As signaling messages may travel over the
Internet, end-to-end security could be required. Internet, end-to-end security between communicating hosts must
be required.
4.7. Flexible multicast distribution 5.7. Multicast considerations
REQ7: DMM should enable multicast solutions in flexible distribution REQ7: DMM should enable multicast solutions in flexible distribution
scenario. This flexibility enables different IP multicast scenario. This flexibility pertains to the preservation of IP
flows with respect to a mobile host to be managed (e.g., multicast nature from the perspective of a mobility entiry and
subscribed, received and/or transmitted) using multiple transmission of mulitcast packets to/from varius multicast-
endpoints. enabled entities. Therefore, this flexibility enables
different IP multicast flows with respect to a mobile host to
be managed (e.g., subscribed, received and/or transmitted)
using multiple multicast-enabled endpoints.
Motivation: The motivation of this requirement is to consider Motivation: The motivation of this requirement is to consider
multicast early so that solutions can be developed to overcome multicast early so that solutions can be developed to avoid
performance issues in multicast distribution scenario. The network inefficiency issues in multicast traffic delivery.
multicast solution may therefore avoid having multicast- The multicast solution should therefore avoid restricting the
capable access routers being restricted to manage all IP managment of all IP multicast traffic relative to a host
multicast traffic relative to a host via a single endpoint through a dedicated interface on multicast-capable access
(e.g., regular or tunnel interface), which would lead to the routers.
problems described in PS1 and PS6.
This requirement addresses the problems PS1 and PS8.
PS8: Duplicate multicast traffic
IP multicast distribution over architectures using IP mobility This requirement addresses the problems PS1 and PS8 in Section 4.
solutions (e.g. 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.
5. Security Considerations 6. Security Considerations
Distributed mobility management (DMM) requires two kinds of security Distributed mobility management (DMM) requires two kinds of security
considerations: First, access network security that only allows a considerations: First, access network security that only allows a
legitimate mobile host/router to access the DMM service; Second, end- legitimate mobile host/router to use DMM; Second, end-to-end security
to-end security that protects signaling messages for the DMM service. between the end hosts, which protects signaling messages for DMM.
Access network security is required between the mobile host/router Access network security is required between the mobile host/router
and the access network providing the DMM service. End-to-end and the access network deploying DMM. End-to-end security is
security is required between nodes that participate in the DMM required between nodes that participate in the DMM protocol.
protocol.
It is necessary to provide sufficient defense against possible It is necessary to provide sufficient defense against possible
security attacks, or to adopt existing security mechanisms and security attacks, or to adopt existing security mechanisms and
protocols to provide sufficient security protections. For instance, protocols to provide sufficient security protections. For instance,
EAP-based authentication can be used for access network security, EAP-based authentication can be used for access network security,
while IPsec can be used for end-to-end security. while IPsec can be used for end-to-end security.
6. IANA Considerations 7. IANA Considerations
None None
7. Co-authors and Contributors 8. Co-authors and Contributors
This problem statement document is a joint effort among the numerous This problem statement document is a joint effort among the numerous
participants. Each individual has made significant contributions to participants. Each individual has made significant contributions to
this work and have been listed as co-authors. this work and have been listed as co-authors.
8. References 9. References
8.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References 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",
draft-ietf-netext-pd-pmip-02 (work in progress),
March 2012.
[I-D.yokota-dmm-scenario] [I-D.yokota-dmm-scenario]
Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case
scenarios for Distributed Mobility Management", scenarios for Distributed Mobility Management",
draft-yokota-dmm-scenario-00 (work in progress), draft-yokota-dmm-scenario-00 (work in progress),
October 2010. October 2010.
[Paper-Distributed.Centralized.Mobility] [Paper-Distributed.Centralized.Mobility]
Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed
or Centralized Mobility", Proceedings of Global or Centralized Mobility", Proceedings of Global
skipping to change at page 15, line 51 skipping to change at page 16, line 15
Networking Technologies, December 2006. Networking Technologies, December 2006.
[Paper-Mobile.Data.Offloading] [Paper-Mobile.Data.Offloading]
Lee, K., Lee, J., Yi, Y., Rhee, I., and S. Chong, "Mobile Lee, K., Lee, J., Yi, Y., Rhee, I., and S. Chong, "Mobile
Data Offloading: How Much Can WiFi Deliver?", SIGCOMM Data Offloading: How Much Can WiFi Deliver?", SIGCOMM
2010, 2010. 2010, 2010.
[RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology", [RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004. RFC 3753, June 2004.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5380] Soliman, H., Castelluccia, C., ElMalki, K., and L. [RFC5380] Soliman, H., Castelluccia, C., ElMalki, K., and L.
Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility
Management", RFC 5380, October 2008. Management", RFC 5380, October 2008.
[RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised",
RFC 5944, November 2010. RFC 5944, November 2010.
[RFC6224] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in Proxy Mobile
IPv6 (PMIPv6) Domains", RFC 6224, April 2011.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011. in IPv6", RFC 6275, July 2011.
[RFC6301] Zhu, Z., Wakikawa, R., and L. Zhang, "A Survey of Mobility [RFC6301] Zhu, Z., Wakikawa, R., and L. Zhang, "A Survey of Mobility
Support in the Internet", RFC 6301, July 2011. Support in the Internet", RFC 6301, July 2011.
[TS.23829] [TS.23.401]
3GPP, "Local IP Access and Selected IP Traffic Offload 3GPP, "General Packet Radio Service (GPRS) enhancements
(LIPA-SIPTO)", 3GPP TR 23.829 10.0.1, October 2011. for Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) access", 3GPP TR 23.401 10.10.0, March 2013.
[TS.29303] [TS.29303]
3GPP, "Domain Name System Procedures; Stage 3", 3GPP 3GPP, "Domain Name System Procedures; Stage 3", 3GPP
TR 23.303 11.2.0, September 2012. TR 23.303 11.2.0, September 2012.
Authors' Addresses Authors' Addresses
H Anthony Chan (editor) H Anthony Chan (editor)
Huawei Technologies (more co-authors on P. 17) Huawei Technologies (more co-authors on P. 17)
5340 Legacy Dr. Building 3, Plano, TX 75024, USA 5340 Legacy Dr. Building 3, Plano, TX 75024, USA
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