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01
IETF INTERNET-DRAFT Thierry Ernst, WIDE and INRIA
Hong-Yon Lach, Motorola Labs Paris
October 2002
Network Mobility Support Terminology
draft-ernst-nemo-terminology-00.txt
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document proposes a terminology for defining network mobility
problems and solution requirements. Network mobility occurs when an
entire network changes its point of attachment to the Internet and
thus its reachability in the topology, which is referred to as a
mobile network.
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Contents
Status of This Memo
Abstract
1. Introduction
2. Applications
3. Terminology
3.1. Architecture Components
Mobile Network
Mobile Network Node (MNN)
Mobile Router (MR)
Fixed Node (FN)
Mobile Node (MN)
Node behind the MR
Correspondent Node (CN)
Access Router (AR)
Egress Interface of a MR
Ingress Interface of a MR
Home subnet prefix
Foreign subnet prefix
Mobile Network Prefix
3.2. Functional Terms
Local Fixed Node (LFN)
Local Mobile Node (LMN)
Visiting Mobile Node (VMN)
NEMO-enabled (NEMO-node)
MIPv6-enabled (MIPv6-node)
3.3. Nested Mobility
root-NEMO
parent-NEMO
sub-NEMO
Top-Level Mobile Router (TLMR)
3.4. Multihomed mobile network
3.5. Miscellaneous Terms
NEMO support
intra-domain mobility
inter-domain mobility
Idle MNN
Idle Mobile Network
Acknowledgments
References
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1. Introduction
A mobile network is an entire network, moving as a unit, which
changes its point of attachment to the Internet and thus its
reachability in the topology. A mobile network may be composed by one
or more IP-subnets and is connected to the global Internet via one or
more Mobile Routers (MR). Nodes behind the MR primarily comprise
fixed nodes (nodes unable to change their point of attachment while
maintaining ongoing sessions), and additionally mobile nodes (nodes
able to change their point of attachment while maintaining ongoing
sessions). The internal configuration of the mobile network is
assumed to be relatively stable with respect to the MR.
If network mobility is not explicitly supported by some mechanisms
once a MR changes its point of attachment, existing sessions between
CNs and nodes behind the MR are broken, and connectivity to the
global Internet is lost. In addition, fixed nodes behind the MR are
faced with sub-optimal routing with their correspondents in the
global Internet, whereas multiple levels of mobility may cause
extremely sub-optimal routing.
Traditional work on mobility support as conducted in the Mobile IP
working group is to provide continuous Internet connectivity to
mobile hosts only (host mobility support) and are unable to support
network mobility. The NEMO working group has therefore been created
to specify solutions specific for network mobility support.
To describe the problems and to define the requirements that will
have to be met by the solutions, a new terminology is needed, which
is the object of the present document. This terminology is supposed
to serve as the base document produced by the NEMO WG and shall be
refined once we agree on the requirements.
2. Applications
Cases of mobile networks include networks attached to people
(Personal Area Network or PAN, i.e. a network composed by all
Internet appliances carried by people, like a PDA, a mobile phone, a
digital camera, a laptop, etc.) and networks of sensors deployed in
aircrafts, boats, busses, cars, trains, etc. An airline company that
provides permanent on-board Internet access is an example of a mobile
network. This allows passengers to use their laptops (this scenario
is mentioned in [Tanenbaum] under section 1.2.4 and section 5.5.8;
[Perkins] under section 5.12; [Solomon] under section 11.2; and
[RFC2002] section 4.5), PDA, or mobile phone to connect to remote
hosts, download music or video, browse the web. Passengers could
themselves carry a network with them (a PAN). At the same time, air
control traffic could be exchanged between the aircraft and air
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traffic control stations (this scenario has already been investigated
by Eurocontrol, the European Organization for the safety of air
navigation. During a transatlantic flight, the aircraft changes its
point of attachment to the Internet and may be reachable by distinct
Internet Service Providers (ISPs). Over the oceans, the aircraft gets
connected to the Internet through a geostationary satellite; over the
ground, it's through a radio link. Handoffs do typically not occur
very often (a radio link may cover 400-500 kilometers). Another
similar scenario mentioning ships and aircrafts can be found in
[RFC1726, section 5.15]. Similarly, a bus, the metropolitan public
transport, or the taxi company could allow passengers to connect
their PAN to the Internet via the embarked network, therefore
ensuring, while on-board, an alternative to the metropolitan cellular
network, in terms of price or available bandwidth, access control,
etc. Meanwhile, a number of Internet appliances deployed in the
mobile network are used to collect traffic and navigation data from
the Internet while sensors within the mobile network collect and
transmit to the Internet live information, like the current number of
passengers, expected time to arrival, the amount of petrol left in
the tank, etc. For a number of reasons (network management, security,
performance,...), it is desirable to interconnect the Internet
appliances deployed in cars, trains, busses by means of, for
instance, an Ethernet cable, instead of connecting them individually
and directly to the Internet, therefore exhibiting the need to
displace an entire network.
3. Terminology
Terms introduced in this draft comply with the terminology already
defined in the IPv6 [RFC2460] and Mobile IPv6 [MIPv6] specifications.
Our terminology is primarily targeted toward IPv6 but is not
necessarily limited to it. Some terms will only be useful for the
purpose of defining the problem scope and functional requirements of
network mobility support and shall be removed or refined once we
agree on the requirements.
The first section introduces terms to define the architecture
components; the second introduces terms to discuss the requirements,
the third, terms to discuss nested mobility; the forth defines
multihoming, and the last, miscellaneous terms which do not fit in
either sections. The terminology summarized in fig.1 to 5. Fig.1
shows a single mobile subnetwork. Fig.2. shows a larger mobile
network comprising several subnetworks, attached on a foreign link.
Fig.3 illustrates a node changing its point of attachment within the
mobile network. Fig.4 and 5 illustrate nested mobility.
3.1. Architecture Components
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Mobile Network
An entire network, moving as a unit, which dynamically changes its
point of attachment to the Internet and thus its reachability in
the topology. The mobile network is connected to the global
Internet via one or more mobile router(s) (MRs). From the fixed
Internet, the mobile network is a cloud. The internal
configuration of the mobile network is assumed to be relatively
stable with respect to the MR and is not a matter of concern. The
internal of the mobile network will therefore not affect network
mobility support protocols.
Mobile Network Node (MNN)
Any host or router located within the mobile network, either
permanently or temporarily. A MNN could be any of a MR, LFN, VMN,
or LMN. The distinction between LFN, LMN and VMN is necessary to
discuss issues related to mobility management and access control,
but does not preclude that mobility should be handled differently.
Nodes are classified according to their function and capabilities.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
______|__ foreign __|_____________ home
link __|_ link
| |
| MR | Mobile Router
|____|
_________|_______ internal
__|__ __|__ link
| | | |
| MNN | | MNN | Mobile Network Nodes
|_____| |_____|
Figure 1: Architecture Components
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Mobile Router (MR)
A router which changes its point of attachment to the Internet.
The MR has one or more egress interface(s) and one or more ingress
interface(s) and acts as a gateway between the mobile network and
the rest of the Internet. The MR thus maintains the Internet
connectivity for the entire mobile network. When forwarding a
packet to the Internet (i.e. upstream), the packet transmitted
through one MR's egress interface; when forwarding a packet to the
mobile network (i.e. downstream), the packet is transmitted
through one of the MR's ingress interface.
Fixed Node (FN)
A node, either a host or a router, unable to change its point of
attachment and its IP address without breaking open sessions. FNs
are standard IPv6 nodes as defined in [IPv6-NODE] which do not
support the MN functionality defined in [MIPv6] section 8.5 nor
any other form of mobility support (also see [IPv6-NODE] section 7
"Mobility").
Mobile Node (MN)
A node, either a host or a router, which is able to change its
point of attachment and maintain continuous sessions.
Node behind the MR
Any MNN in a mobile network, beside the MRs connecting the mobile
network to the Internet.
Correspondent Node (CN)
Any node that is communicating with one or more MNNs. A CN could
itself be located within the mobile network.
Access Router (AR)
Any subsequent point of attachment of the MR at the network layer.
Basically, a router on the home link or the foreign link. An AR
may itself be located in a mobile network and provide access to
mobile nodes.
Egress Interface of a MR
The interface attached to the home link if the MR is at home, or
attached to a foreign link if the MR is in a foreign network.
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Ingress Interface of a MR
The interface attached to a link inside the mobile network. This
interface is configured with the Mobile Network Prefix.
________________________
| |
| |
| Internet |
| |
|________________________|
__|_
Access | |
Router | AR |
|____|
foreign _____|_____________
link |
| egress interface
__|__
| | |
ingress |____| MR | Mobile Router
interface | |____|
| |
| | ingress interface
| ____|________________ internal
| __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal
link 2
Figure 2: Larger Mobile Network with 2 subnets
Home subnet prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the MR's home link within the Internet
topology (i.e. the IP subnet prefix corresponding to the mobile
node's home address, as defined in [MIPv6]).
Foreign subnet prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the MR's foreign link within the Internet
topology.
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Mobile Network Prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the entire mobile network within the
Internet topology. All MNNs necessarily have an address named
after this prefix.
3.2. Functional Terms
The distinction between LFN, LMN, and VMN as defined below it is a
property of how different types of nodes can move in the topology.
The rationale here is that nodes with different properties (may) have
different requirements. This distinction may not be useful once we
agree on the requirements. They are listed here as a means to ease
and clarify the requirement discussion.
Local Fixed Node (LFN)
A fixed node (FN) that belongs to the mobile network and which
doesn't move topologically with respect to the MR.
Local Mobile Node (LMN)
A mobile node (MN) or a mobile router (MR) that belongs to the
mobile network (i.e. its home link is within the mobile network).
It can move topologically with respect to the MR.
Visiting Mobile Node (VMN)
A mobile node (MN) or a mobile router (MR) that doesn't belong to
the mobile network (i.e. its home link is not within the mobile
network). A VMN that gets attached to a link within the mobile
network obtains an address on that link and can move topologically
with respect to the MR.
NEMO-enabled (NEMO-node)
A node that has been extended with network mobility support
capabilities and that may take special actions based on that.
(details of the capabilities are not known yet, but it may be
implementing some sort of Route Optimization).
MIPv6-enabled (MIPv6-node)
A mobile node (MN) which is able to change its point of attachment
and maintains continuous sessions thanks to the MN functionality
as defined in [MIPv6] section 8.5.
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________________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
__|_ _____|_____________ foreign
| | _|__ link
| MN | | | |
|____| _____ |__| MR | Mobile Router
| |__| |____|
|--> | LMN | | __|_____________ internal
| |_____| | __|__ | link 1
| _____ | | |
| | |__| | LFN |
| | LFN | | |_____| |
| |_____| | |
| | internal |
| link 2 |
|------------------------------|
Figure 3: LMN changing subnet
3.3. Nested Mobility
Nested mobility occurs when there are more than one level of
mobility. A MNN acts as an Access Router and allows visiting nodes to
get attached to it. There are two cases of nested mobility:
- when the attaching node is a single node: VMN (see figure 4).
For instance, when a passenger carrying a mobile phone gets
Internet access from the public access network deployed into a
bus.
- when the attaching node is a router with nodes behind it,
i.e.a mobile network (see figure 5). For instance, when a
passenger carrying a PAN gets Internet access from the public
access network deployed in the bus.
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________________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ home
| _|__ link
| | | |
| _____ |__| MR | Mobile Router
| | |__| |____|
----------> | VMN | | __|_____________ internal
|_____| | __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal link 2
Figure 4: Nested Mobility: single VMN attached to a mobile network
In the second case, a mobile network is getting attached to a
larger mobile network and the aggregated hierarchy of mobile
networks becomes a single nested mobile network. In this case, we
use the following terms:
- root-NEMO: the mobile network at the top of the nested
hierarchy.
- parent-NEMO: the upstream-NEMO providing access to a mobile
network down the hierarchy
- sub-NEMO: the downstream-NEMO attached to a mobile network up
the hierarchy. It becomes a subservient of the parent-NEMO.
- Top-Level Mobile Router (TLMR): the MR(s) of the root-NEMO
which are used to connect the nested mobile network to the
fixed Internet.
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________________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ foreign
_|__ link
| | |
| ____ |__| MR | Mobile Router (TLMR)
|_| |__| |____|
| | MR | | __|_____________ internal
| |____| | __|__ __|__ link 1
_____ | | | | | |
| | | | | LFN | | LMN |
| LFN |__| | |_____| |_____|
|_____| | |
| | internal
link 2
<-----------------> <--------------------------->
sub-NEMO root-NEMO
Figure 5: Nested Mobility: sub-NEMO attached to a larger mobile network
3.4. Multihomed mobile network
Multihoming, as currently defined by the IETF, covers site-
multihoming [MULTI6] and host multihoming. Within host-multihoming, a
host may be either:
- multi-addressed: multiple source addresses to choose between on
a given interface; all IPv6 nodes are multi-addressed due to the
presence of link-local addresses on all interfaces.
- multi-interfaced: multiple interfaces according to [RFC2460]
definition.
- multi-linked: just like multi-interfaced but all interfaces are
NOT connected to the same link.
- multi-sited: when using IPv6 site-local address and attached to
different sites
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So, a mobile network is multihomed when either:
- a MR has multiple egress interfaces on the same foreign link
- a MR has multiple egress interfaces on distinct foreign link
- there are more than one MR in the mobile network
3.5. Miscellaneous Terms
Host mobility support
Host Mobility Support allows mobile nodes to maintain session
continuity. In IPv6, it is achieved by Mobile IPv6
NEMO support
Network mobility support allows mobile networks to maintain
session continuity. Solutions developped to support NEtwork
MObility will be referred to as "NEMO support".
In Basic support, each Mobile Router has a Home Agent, and uses
bidirectional tunneling between the MR and HA to preserve session
continuity while the MR moves. The MR will acquire a Care-of-
address from its attachment point much like what is done for
Mobile Nodes using Mobile IP. This approach allows nesting of
Nemos, since each MR will appear to its attachment point as a
single node.
In Extended support, we will seek to optimize routing between MNNs
and arbitrary CNs by some means which details are not known yet.
intra-domain mobility
Mobility within a single administrative domain, i.e. between
subnetworks topologically close in the IP hierarchy. As an
instance, the displacement of a node within a limited vicinity of
adjacent subnetworks, like in a campus, that belong to the same
organization or between ARs that belong to the same ISP. In the
literature, and depending on the definition of ``closeness'', this
is also termed intra-site mobility, local mobility or micro-
mobility.
inter-domain mobility
Mobility across administrative domain boundaries, i.e. between
subnetworks topologically distant in the IP hierarchy. As an
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instance of Wide-Area Mobility, displacement of a node between
distinct ISPs or organizations, or between widely separated sites
of a single organization. In the literature, and depending on the
definition of ``remoteness'', this is also termed inter-site
mobility, global mobility, or macro-mobility.
Idle MNN
A MNN that does not engage in any communication.
Idle Mobile Network
A mobile network that does not engage in any communication outside
the network may be considered idle from the global Internet. This
doesn't preclude that MNNs are themselves idle. Internal traffic
between any two MNNs located in the same mobile network is not
concerned by this statement.
Acknowledgments
The material presented in this document takes most of the text from
our former internet-drafts submitted to MobileIP WG and to the former
MONET BOF, which where themselves based on original text from
[Ernst01]. Authors would therefore like to thank both Motorola Labs
Paris and INRIA (PLANETE team, Grenoble, France), for the opportunity
to bring this topic to the IETF since 2000, and particularly Claude
Castelluccia (INRIA) for its advices, suggestions, and direction. We
also acknowledge Alexandru Petrescu (Motorola), Christophe Janneteau
(Motorola), Hesham Soliman (Ericsson) and Mattias Petterson
(Ericsson) and all the people on the NEMO (formerly MONET) mailing
list which helped to improve this draft.
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References
[Ernst01] Thierry Ernst
Network Mobility Support in IPv6", PhD Thesis,
University Joseph Fourier Grenoble, France.
October 2001. http://www.inria.fr/rrrt/tu-0714.html
[MIPv6] David B. Johnson and C. Perkins.
"Mobility Support in IPv6".
Internet Draft draft-ietf-mobileip-ipv6-18.txt,
July 2002. Work in progress.
[MULTI6] B. Black, V. Gill and J. Abley
"Requirements for IPv6 Site-Multihoming Architectures"
draft-ietf-multi6-multihoming-requirements-03
May 2002. Work in progress
[IPv6-NODE] John Loughney
"IPv6 Node Requirements"
draft-ietf-ipv6-node-requirements-01.txt
July 2002, Work in progress.
[Perkins] C. E. Perkins.
"Mobile IP, Design Principles and Practices."
Wireless Communications Series.
Addison-Wesley, 1998. ISBN 0-201-63469-4.
[RFC1726] C. Partridge
"Technical Criteria for Choosing IP the Next Generation",
IETF RFC 1726 section 5.15, December 1994.
[RFC2460] S. Deering and R. Hinden.
"Internet Protocol Version 6 (IPv6) Specification".
IETF RFC 2460, December 1998.
[RFC2002] C. Perkins (Editor).
"IP Mobility Support".
IETF RFC 2002,October 1996.
[Solomon] J. D. Solomon.
"Mobile IP, The Internet Unplugged".
Prentice Hall Series in Computer Networking
and Distributed Systems.
Prentice Hall PTR, 1998. ISBN 0-13-856246-6.
[Tanenbaum] Andrew Tanenbaum
"Computer Networks",
Prentice-Hall, Third Edition. 1996
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Author's Addresses
Questions about this document can be directed to the authors:
Thierry Ernst,
INRIA, visiting researcher at WIDE
Jun Murai lab. Faculty of Environmental Information,
Keio University.
5322 Endo, Fujisawa-shi, Kanagawa 252-8520, Japan.
Phone : +81-466-49-1100
Fax : +81-466-49-1395
E-mail: ernst@sfc.wide.ad.jp
Web: http://www.sfc.wide.ad.jp/~ernst/
Hong-Yon Lach
Motorola Labs Paris, Lab Manager,
Networking and Applications Lab (NAL)
Espace Technologique - Saint Aubin
91193 Gif-sur-Yvette Cedex, France
Phone: +33-169-35-25-36
Email: Hong-Yon.Lach@crm.mot.com
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