IETF INTERNET-DRAFT Thierry Ernst
WIDE Project / INRIA
Hong-Yon Lach
Motorola Labs
February 2002
Network Mobility Support Terminology
draft-ernst-monet-terminology-00.txt
Status of This Memo
This document is an Internet-Draft and is in full conformance with
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Abstract
The purpose of traditional mobility support is to provide continuous
Internet connectivity to mobile hosts (host mobility support). In
contrast, network mobility support is concerned with situations where
an entire network changes its point of attachment to the Internet and
thus its reachability in the topology. We shall refer to such a
network as a mobile network (MONET). There is presently no existing
terminology to define the issues, goals, architecture elements,
problems and requirements pertaining to network mobility support, but
one is needed. It is therefore the object of this document to define
a new terminology, to depict the characteristics of mobile networks
and to make some observations.
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Contents
Status of This Memo
Abstract
1. Introduction
2. Terminology
2.1. Architecture Components
2.2. Other Terminology
3. Characteristics / Observations
Acknowledgments
References
Author's Addresses
1. Introduction
The purpose of traditional mobility support is to provide continuous
Internet connectivity to mobile hosts (host mobility support). In
contrast, network mobility support is concerned with situations where
an entire network changes its point of attachment to the Internet and
thus its reachability in the topology. We shall refer to such a
network as a mobile network (MONET).
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 [Tanenbaum96] under section 1.2.4 and section 5.5.8;
[Perkins98] under section 5.12; [Solomon98] 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
traffic control stations (this scenario has already been investigated
by Eurocontrol, the European Organization for the safety of air
navigation, [Quinot98]). 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
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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.
To describe such kind of scenarios, we need to agree on a
terminology. However, there is presently no existing terminology to
define the issues, goals, architecture elements, problems and
requirements pertaining to the scenarios outlined here above, but one
is needed. It is therefore the object of this document to define such
a new terminology and to make some observations. The material
presented in this document is based on [Ernst01] and on our former
internet-draft that was submitted in July 2001 [OLD-draft] for the
consideration of the Mobile IP Working Group. In addition to the
present terminology, this former draft was also presenting a set of
requirements and issues as an attempt to clarify the problem caused
by networks in motion. We decided to split this former document in
two because requirements are more subject to discussion and
disagreements that the terminology on which we must agree on to base
our discussion. Our proposed requirements can therefore now be found
in [REQUIREMENTS]. Additional requirements may be found in
[REQUIREMENTS-NOKIA] and [REQUIREMENTS-MOTOROLA]. A comprehensive
description of the problem and issues posed by networks in motion is
discussed in [SCOPE]. More information may be found on the MONET web
page [WEB-MONET].
2. Terminology
Our proposed terminology defines a number of new terms in conformance
with the terminology already defined in the IPv6 [RFC2460] and Mobile
IPv6 [MIPv6] specifications. Note that our terminology is primarily
targeted to IPv6, but is not limited to it. The first section defines
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the architecture components, and the second section defines a number
of other terms useful to discuss requirements.
2.1. Architecture Components
Mobile Network (MONET)
A set of nodes composed by one or more IP-subnets attached to a
mobile router (MR) and mobile as a unit, with respect to the rest
of the Internet, i.e. a MR and all its attached nodes. The MR
changes dynamically its point of attachment to the Internet and
thus its reachability in the Internet.
Mobile IP-subnet
A MONET composed of a single IP-subnet.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
______|__ foreign __|_____________ home
link __|_ link
| |
| MR | Mobile Router
|____|
_________|_______ internal
__|__ __|__ link
| | | |
| MNN | | MNN | Mobile Network Nodes
|_____| |_____|
Figure 1: Terminology
Mobile Network Node (MNN)
Any host or router located within the MONET, 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
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issues related to mobility management and access control, but does
not preclude that mobility should be handled differently.
Mobile Router (MR)
A router which attaches the MONET to the rest of the Internet. The
MR maintains the Internet connectivity for the MONET. It is used
as a gateway to route packets between the MONET and the Internet.
The MR has at least two interfaces, an egress interface, and an
ingress interface. When transmitting a packet to the Internet
(i.e. outside), it sends it through the egress interface; when
transmitting it withing the MONET (i.e. inside), it sends it
through the ingress interface.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
__|_ _____|_____________ home
| | _|__ link
| MN ] | | |
|____| |__| MR | Mobile Router
| |____|
| __|_____________ internal
| __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal
link 2
Figure 2: Larger Mobile Network with 2 subnets
Local Fixed Node (LFN)
A node permanently located within the MONET and that does not
change its point of attachment. A LFN can either be a LFH (Local
Fixed Host) or a LFR (Local Fixed Router).
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Local Mobile Node (LMN)
A mobile node that belongs to the MONET and that changes its point
of attachment from a link within the mobile network to another
link within or outside the MONET (the home link of the LMN is a
link within MONET). A LMN can either be a LMH (Local Mobile Host)
or a LMR (Local Mobile Router).
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
__|_ _____|_____________ home
| | _|__ link
| MN | | | |
|____| _____ |__| MR | Mobile Router
| |__| |____|
|--> | LMN | | __|_____________ internal
| |_____| | __|__ | link 1
| _____ | | |
| | |__| | LFN |
| | LFN | | |_____| |
| |_____| | |
| | internal |
| link 2 |
|------------------------------|
Figure 3: LMN changing subnet
Visiting Mobile Node (VMN)
A mobile node that does not belong to the MONET and that changes
its point of attachment from a link outside the MONET to a link
within the MONET (the home link of the VMN is not a link within
the MONET). A VMN that attaches to a link within the MONET obtains
an address on that link. A VMN can either be a VMH (Visiting
Mobile Host) or a VMR (Visiting Mobile Router).
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Top-Level Mobile Router (TLMR)
In case there are more MONETs aggregated into the MONET, the TLMR
is the MR(s) used to direcly connect the aggregated MONET to the
fixed Internet.
Node behind the MR
Any MNN in a MONET that is not a MR for this MONET.
Correspondent Node (CN) of a MONET
Any node located outside the MONET that is communicating with one
or more MNNs. CNs corresponding with MNNs located in the same
MONET are said to be CNs of this MONET.
Access Router (AR)
Any subsequent point of attachment of the MONET at the network
layer. Basically, a router on the home link or the foreign link.
When considering nested mobility, an AR seen by the MONET may be a
MR or a LFR for the entire network.
Home subnet prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the 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 a foreign link within the Internet
topology.
Mobile Network Prefix
A bit string that consists of some number of initial bits of an IP
address which identifies a MONET within the Internet topology.
Nodes belonging to the MONET (i.e. at least MR, LFNs and LMNs)
share the same IPv6 "network identifier". For a single mobile IP-
subnet, the Mobile Network Prefix is the "network identifier" of
this subnet.
Egress Interface of a MR
The interface attached to the home link if the MONET is at home,
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or attached to a foreign link if the MONET is in a foreign
network.
Ingress Interface of a MR
The interface attached to a link inside the MONET. This interface
is configured with the Mobile Network Prefix.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ home
| _|__ link
| | | |
| _____ |__| MR | Mobile Router
| | |__| |____|
----------> | VMN | | __|_____________ internal
|_____| | __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal
link 2
Figure 4: Nested Mobility: Visiting Mobile Node (VMN)
The terminology is summarized in fig.1 and to 5. Fig.1 shows a single
mobile IP-subnet. Fig.2. shows a large mobile network. Fig.3
illustrates a LMN changing subnet within the mobile network whereas
fig.4 illustrates the case of a VMN that enters the mobile network.
Fig 5. illustrates the case of a mobile IP-subnet that attaches to a
MONET.
2.2. Other Terminology
Nested mobility
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We speak about nested mobility when a MONET comprises mobile nodes
(LMNs or VMNs) and even MONETs. In the bus instance, the bus is a
MONET whereas a passenger is either a VMN in a MONET if it carries
a mobile phone or a MONET in the MONET if it carries a PAN.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ home
_|__ link
| | |
| _____ |__| MR | Mobile Router (TLMR)
|_| |__| |____|
| | VMR | | __|_____________ internal
| |_____| | __|__ __|__ link 1
_____ | | | | | |
| | | | | LFN | | LMN |
| LFN |__| | |_____| |_____|
|_____| | |
| | internal
link 2
Figure 5: Nested Mobility: mobile IP-subnet in a MONET
Multi-Homing
A MONET is multi-homed when it has two or more active egress
interfaces connected to distinct parts of the Internet. This could
either be a single MR with two egress interfaces simultaneously
connected to the Internet, or the MONET may be connected to the
Internet via two or more MRs. In the first case, we could think of
a unique router used to connect a car both to the cellular phone
network and to a satellite. In the second case, we may think of a
PAN where a phone is used to connect the PAN to the cellular phone
network whereas a Bluetooth PDA is used to collect bus timetables
from the city bus network. In this situation both the phone and
the PDA are MRs.
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Local-Area Mobility
Mobility within a single administrative domain, i.e. between
subnetworks topologically close in the IP hierarchy. In the
literature, and depending on the definition of ``closeness'', this
is also termed intra-site mobility, intra-domain mobility, local
mobility or micro-mobility. As an instance of Local-Area Mobility,
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.
Wide-Area Mobility
Mobility across domain boundaries, i.e. between subnetworks
topologically distant in the IP hierarchy. In the literature, and
depending on the definition of ``remoteness'', this is also termed
inter-site mobility, inter-domain mobility, or global mobility, or
macro-mobility. As an instance of Wide-Area Mobility, displacement
of a node between distinct ISPs or organizations, or between
widely separated sites of a single organization.
Idle MNN
A MNN that does not engage in any communication.
Idle Mobile Network
A MONET that does not engage in any communication outside the
network may be considered as idle from the point of view of the
Internet. This doesn't preclude that MNNs are themselves idle.
Internal traffic between any two MNNs located in the same MONET is
not concerned by this statement.
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3. Observations
Structure of the mobile network
A MR changing its point of attachment does not cause the MNNs
behind the MR to change their own physical point of attachment.
Thus, the internal structure of a MONET is not modified as a
result of the MONET changing its point of attachment and a MNN may
not notice such a displacement. However, MNNs MAY appear to move
from the point of view of an other node in the Internet.
Mobile Router is a transit point
All packets sent from a CN to a MNN necessarily transit through a
MR.
Size of the MONET
A MONET may comprise one or more subnets. Its size could scale
from a sole subnet with a few IP devices, such as in the case of a
PAN, to a collection of subnets with hundreds of IP devices, such
as in a train.
Large number of CNs
A MONET may have a very large number of CNs. For instance, each
passenger in a train may be considered a MNN. Each of them may be
communicating with a few CNs. As a result, the total number of CNs
could be several times as large as the number of MNNs and scale up
to a few thousands.
Sparseness of the CNs
CNs are typically sparsely distributed in the Internet and belong
to distinct administrative domains.
Handoff frequency
MONETs may not move with the same speed and frequency. For
instance, a PAN connected to the Internet via a 802.11b WLAN (e.g.
user in a shopping mall) is likely to change its point of
attachment very frequently, while an aircraft or a boat may be
connected to the Internet via the same satellite link for a couple
of hours. Obviously, MONETs may not move at all for a large amount
of time.
Ad-Hoc Network
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An Ad-hoc network as defined in the IETF MANET Working Group is
not to be confused with a MONET. An ad-hoc network is an
autonomous system of mobile nodes (i.e. routers) connected by
wireless links. The routers are free to move randomly and to
organize themselves arbitrary. In a mobile network, some routers
may effectively move arbitrary, but this not a common case.
However, an Ad-hoc network connected to the Internet and that
changes its point of attachment may be considered as a special
instance of a MONET.
Routers in the Mobile Network
All routers in the Internet are considered to run a number of
protocols such as a routing protocol, Neighbor Discovery, ICMP,
and others. This also applies to routers in the MONET, including
the MR.
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Acknowledgments
The first author would like to thank both Motorola Labs Paris and
INRIA Rhône-Alpes, for the opportunity to bring this topic to the
IETF, 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) for their comments on
this draft.
References
[Ernst01] Thierry Ernst "Network Mobility Support in IPv6", PhD
Thesis, University Joseph Fourier Grenoble, France. October 2001.
[MIPv6] David B. Johnson and C. Perkins. "Mobility Support in IPv6".
Internet Draft draft-ietf-mobileip-ipv6-14.txt, Internet Engineering
Task Force (IETF), July 2001. Work in progress.
[OLD-draft] Thierry Ernst, Hong-Yon Lach, Claude Castelluccia
"Network Mobility Support in IPv6: Problem Statement and
Requirements", IETF Internet-Draft draft-ernst-mobileip-
monetv6-00.txt, July 2001. Expiration pending.
[Perkins98] C. E. Perkins. Mobile IP, Design Principles and
Practices. Wireless Communications Series. Addison-Wesley, 1998. ISBN
0-201-63469-4.
[Quinot98] Thomas Quinot. An IPv6 architecture for Aeronautical
Telecommunication Network. Master's thesis, Ecole Nationale
Superieure des Telecommunications Paris, EUROCONTROL - European
Organization for the Safety of Air Navigation - ISA project (IPv6,
Satellite communication and ATMode for ATN), 1998.
http://www.eurocontrol.fr/.
[RFC1726] C. Partridge "Technical Criteria for Choosing IP the Next
Generation (IPng)", IETF RFC 1726 section 5.15, December 1994.
[RFC2460] S. Deering and R. Hinden. "Internet Protocol Version 6
(IPv6) Specification". IETF RFC 2460, Internet Engineering Task
Force (IETF), December 1998.
[RFC2002] C. Perkins (Editor). IP Mobility Support. IETF RFC 2002,
October 1996.
[REQUIREMENTS] Thierry Ernst "Requirements for Network Mobility
Support", IETF Internet-Draft draft-ernst-monet-requirements-00.txt,
February 2001. Work in progress.
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[REQUIREMENTS-MOTOROLA] Hong-Yon Lach "Mobile Network Scenarios,
Scope and Requirements", IETF Internet-Draft draft-lach-monet-
requirements-00.txt, February 2002. Work in progress.
[REQUIREMENTS-NOKIA] draft-kniveton-monet-requirements.txt, February
2002. Work in progress.
[SCOPE] Hesham Soliman "Problem Scope", IETF Internet-Draft draft-
soliman-monet-scope-00.txt, February 2002. Work in progress.
[Solomon98] 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.
[Tanenbaum96] Andrew Tanenbaum "Computer Networks", Prentice-Hall,
Third Edition. 1996
[WEB-MONET] MONET web page http://www.nal.motlabs.com/monet
Author's Addresses
Questions about this document can be directed to the authors:
Thierry Ernst,
WIDE Project
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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