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Differences from draft-ietf-nemo-requirements-02.txt
NEMO Working Group T. Ernst
Internet-Draft WIDE at Keio University
Expires: April 25, 2005 October 25, 2004
Network Mobility Support Goals and Requirements
draft-ietf-nemo-requirements-03
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
Network mobility arises when a router connecting an entire network to
the Internet dynamically changes its point of attachment to the
Internet therefrom causing the reachability of the entire network to
be changed in the topology. Such kind of network is referred to as a
mobile network. Without appropriate mechanisms, sessions established
between nodes in the mobile network and the global Internet cannot be
maintained while the mobile router changes its point of attachment.
The required support mechanisms will be provided in two phases. The
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first phase, referred to as NEMO Basic Support is to provide session
continuity while the necessary optimizations mechanims referred to as
NEMO Extended Support might be provided later. This document
outlines the goals expected from network mobility support and defines
the requirements that must be met by NEMO Basic Support solutions.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. NEMO Working Group Objectives and Methodology . . . . . . . 4
3. NEMO Support Design Goals . . . . . . . . . . . . . . . . . 5
3.1 Migration Transparency . . . . . . . . . . . . . . . . . . 5
3.2 Performance Transparency and Seamless Mobility . . . . . . 5
3.3 Network Mobility Support Transparency . . . . . . . . . . 5
3.4 Operational Transparency . . . . . . . . . . . . . . . . . 6
3.5 Arbitrary Configurations . . . . . . . . . . . . . . . . . 6
3.6 Local Mobility and Global Mobility . . . . . . . . . . . . 7
3.7 Scalability . . . . . . . . . . . . . . . . . . . . . . . 7
3.8 Backward Compatibility . . . . . . . . . . . . . . . . . . 7
3.9 Secure Signaling . . . . . . . . . . . . . . . . . . . . . 8
3.10 Location Privacy . . . . . . . . . . . . . . . . . . . . 8
3.11 IPv4 and NAT Traversal . . . . . . . . . . . . . . . . . 8
4. NEMO Basic Support One-Liner Requirements . . . . . . . . . 8
5. Changes Between Versions . . . . . . . . . . . . . . . . . . 10
5.1 Changes between version -02 and -03 . . . . . . . . . . . 10
5.2 Changes Between Version -01 and -02 . . . . . . . . . . . 10
5.3 Changes Between Version -00 and -01 . . . . . . . . . . . 11
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . 13
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1. Introduction
Network mobility support is concerned with managing the mobility of
an entire network, viewed as a single unit, which changes its point
of attachment to the Internet and thus its reachability in the
Internet topology. Such kind of network is referred to as a mobile
network and includes one or more mobile routers (MRs) which connect
it to the global Internet. Nodes behind the MR(s) (MNNs) are both
fixed (LFNs) and mobile (VMNs or LMNs). In most cases, the internal
structure of the mobile network will in effect be relatively stable
(no dynamic change of the topology), but this is not a general
assumption.
Cases of mobile networks include for instance:
o networks attached to people (Personal Area Networks or PANs): a
cell-phone with one cellular interface and one Bluetooth interface
together with a Bluetooth-enabled PDA constitute a very simple
instance of a mobile network. The cell-phone is the mobile router
while the PDA is used for web browsing or runs a personal web
server.
o networks of sensors and computers deployed in vehicles: vehicles
are more and more embedded with a number of processing units for
safety and ease of driving reasons, as advocated by ITS
(Intelligent Transportation Systems) applications.
o access networks deployed in public transportation (buses, trains,
taxis, aircrafts): they provide Internet access to IP devices
carried by passengers (laptop, camera, mobile phone: host mobility
within network mobility or PANs: network mobility within network
mobility, i.e. nested mobility).
o ad-hoc networks connected to the Internet via a MR: for instance
students in a train that both need to set up an ad-hoc network
among themselves and to get Internet connectivity through the MR
connecting the train to the Internet.
Mobility of networks does not cause MNNs to change their own physical
point of attachment, however they happen to change their topological
location with respect to the global Internet. If network mobility is
not explicitly supported by some mechanisms, the mobility of the MR
results into MNNs losing Internet access and breaking ongoing
sessions entertained between arbitrary correspondent node (CNs) in
the global Internet and those MNNs located within the mobile network.
In addition, the communication path between MNNs and arbitrary
correspondent nodes (CN) becomes sub-optimal, whereas multiple levels
of mobility will cause extremely sub-optimal routing.
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The mechanisms required for handling such mobility issues are
currently lacking within the IETF standards. Traditional work
conducted on mobility support (particularly in the Mobile IP working
group) is to provide continuous Internet connectivity and optimal
routing to mobile hosts only (host mobility support) and are unable
to support network mobility. The NEMO working group has therefore
been set up to deal with issues specific to network mobility. The
purpose of this document is thus to detail the methodology that will
be followed by the NEMO working group, its goals, and to define
requirements for network mobility support.
Mobility-related terms used in this document are defined in [3]
whereas terms pertaining to network mobility specifically are defined
in [4]. This document is structured as follows: Section 2 defines
the rough objectives and methodology of the NEMO working group and we
emphasize the stepwise approach the working group has decided to
follow. A number of desirable design goals are listed in Section 3.
Those design goals serve as guidelines to edict the requirements
listed in Section 4 for basic network mobility support [2].
2. NEMO Working Group Objectives and Methodology
The primary objective of the NEMO work is to specify a solution which
allows mobile network nodes (MNNs) to remain connected to the
Internet and continuously reachable at all times while the mobile
network they are attached to changes its point of attachment.
Secondary goals of the work is to investigate the effects of network
mobility on various aspects of internet communication such as routing
protocol changes, implications of realtime traffic and fast
handovers, optimizations. These should all support the primary goal
of reachability for mobile network nodes. Security is an important
consideration too, and efforts should be made to use existing
solutions if they are appropriate. Although a well-designed solution
may include security inherent in other protocols, mobile networks
also introduce new challenges.
For doing so, the NEMO working group has decided to take a stepwise
approach by standardizing a basic solution to preserve session
continuity (NEMO Basic Support), and at the same time study the
possible approaches and issues with providing more optimal routing
with potentially nested mobile networks (NEMO Extended Support).
However, the working group is not chartered to actually standardize a
solution to such route optimization at this point in time.
For NEMO Basic Support, the working group will assume that none of
the nodes behind the MR will be aware of the network's mobility, thus
the network's movement needs to be completely transparent to the
nodes inside the mobile network. This assumption will be made to
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accommodate nodes inside the network that are not generally aware of
mobility.
The efforts of the Mobile IP working group have resulted in the
Mobile IPv4 and Mobile IPv6 protocols, which have already solved the
issue of host mobility support. Since challenges to enabling mobile
networks are vastly reduced by this work, basic network mobility
support will adopt the methods for host mobility support used in
Mobile IP, and extend them in the simplest way possible to achieve
its goals. The basic support solution is for each MR to have a Home
Agent, and use 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 (MN) using Mobile IP. This approach allows nested
mobile networks, since each MR will appear to its attachment point as
a single node.
3. NEMO Support Design Goals
This section details the fundamental design goals the solutions will
tend to achieve. Those design goals will serve to edict and
understand the requirements defined for forthcoming solutions.
Actual requirements for NEMO Basic Support are in the next section,
whereas NEMO Extended Support has not yet been considered.
3.1 Migration Transparency
A permanent connectivity to the Internet has to be provided to all
MNNs while continuous sessions are expected to be maintained as the
mobile router changes its point of attachment. For doing so, MNNs
are expected to be reachable via their permanent IP addresses.
3.2 Performance Transparency and Seamless Mobility
NEMO support is expected to be provided with limited signaling
overhead and to minimize the impact of handover over applications, in
terms of packet loss or delay. However, although variable delays of
transmission and losses between MNNs and their respective CNs could
be perceived as the network is displaced, it would not be considered
a lack of performance transparency.
3.3 Network Mobility Support Transparency
MNNs behind the MR(s) don't change their own physical point of
attachment as a result of the mobile network's displacement in the
Internet topology. Consequently, NEMO support is expected to be
performed by the sole MR(s) and specific support functions on any
other node than the MR(s) would better be avoided.
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3.4 Operational Transparency
NEMO support is to be implemented at the IP layer level. It is
expected to be transparent to upper layers so that any upper layer
protocol can run unchanged on top of an IP layer extended with NEMO
support.
3.5 Arbitrary Configurations
The formation of a mobile network can exist in various levels of
complexity. In the simplest case, a mobile network contains just a
mobile router and a host. In the most complicated case, a mobile
network is multihomed and is itself a multi-level aggregation of
mobile networks with collectively thousands of mobile routers and
hosts. While the list of potential configurations of mobile networks
cannot be limited, at least the following configurations are
desirable:
o mobile networks of any size, ranging from a sole subnet with a few
IP devices to a collection of subnets with a large number of IP
devices,
o nodes that change their point of attachment within the mobile
network,
o foreign mobile nodes that attach to the mobile network,
o multihomed mobile network either when a single MR has multiple
attachments to the internet, or when the mobile network is
attached to the Internet by means of multiple MRs (see definition
in [4] and the analys in [5]),
o nested mobile networks (mobile networks attaching to other mobile
networks (see definition in [4]). Although the complexity
requirements of those nested networks is not clear, it is
desirable to support arbitrary levels of recursive networks, and
only in the case where this is impractical and protocol concerns
preclude this support should the solution impose restrictions on
nesting (e.g. path MTU),
o distinct mobility frequencies (see mobility factor in [3])
o distinct access medium.
In order to keep complexity minimal, transit networks are excluded
from this list. A transit network is one in which data would be
forwarded between two endpoints outside of the network, so that the
network itself simply serves as a transitional conduit for packet
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forwarding. A stub network (leaf network), on the other hand, does
not serve as a data forwarding path. Data on a stub network is
either sent by or addressed to a node located within that network.
3.6 Local Mobility and Global Mobility
Mobile networks and mobile nodes owned by administratively different
entities are expected to be displaced within a domain boundary or
between domain boundaries. Multihoming, vertical and horizontal
handoffs, and access control mechanisms are desirable to achieve this
goal. Such mobility type is not expected to be limited for any
consideration other than administrative and security policies.
3.7 Scalability
NEMO support signaling and processing is expected to scale to a
potentially large number of mobile networks irrespective of their
configuration, mobility frequency, size and number of CNs.
3.8 Backward Compatibility
NEMO support will have to co-exist with existing IPv6 standards
without interfering with them. Standards defined in other IETF
working groups have to be reused as much as possible and extended
only if deemed necessary. For instance, the following mechanisms
defined by other working groups are expected to function without
modidications:
o Address allocation and configuration mechanisms
o Host mobility support: mobile nodes and correspondent nodes,
either located within or outside the mobile network are expected
to keep operating protocols defined by the Mobile IP working
group. This include mechanisms for host mobility support (Mobile
IPv6) and seamless mobility (FMIPv6).
o Multicast support entertained by MNNs are expected to be
maintained while the mobile router changes its point of
attachment.
o Access control protocols and mechanisms used by visiting mobile
hosts and routers to be authenticated and authorized to gain
access to the Internet via the mobile network infrastructure
(MRs).
o Security protocols and mechanisms
o Mechanisms performed by routers deployed both in the visited
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networks and in mobile networks (routing protocols, Neighbor
Discovery, ICMP, Router Renumbering, ...).
3.9 Secure Signaling
NEMO support will have to comply with usual IETF security policies
and recommendations and is expected to have its specific security
issues fully addressed. In practice, all NEMO support control
messages transmitted in the network will have to ensure an acceptable
level of security to prevent intruders to usurp identities and forge
data. Specifically, the following issues have to be considered:
o Authentication of the sender to prevent identity usurpation.
o Authorization, to make sure the sender is granted permission to
perform the operation as indicated in the control message.
o Confidentiality of the data contained in the control message.
3.10 Location Privacy
Means to hide the actual location of MNNS to third parties other than
the HA are desired. In which extend this has to be enforced is not
clear since it is always possible to determine the topological
location by analysing IPv6 headers. It would thus require some kind
of encryption of the IPv6 header to prevent third parties to monitor
IPv6 addresses between the MR and the HA. On the other hand, it is
at the very least desirable to provide means for MNNs to hide their
real topological location to their CNs.
3.11 IPv4 and NAT Traversal
IPv4 clouds and NAT are likely to co-exist with IPv6 for a long time,
so it is desirable to ensure mechanisms developped for NEMO will be
able to traverse such clouds.
4. NEMO Basic Support One-Liner Requirements
The NEMO WG is to specify a unified and unique "Network Mobility
Basic Support" solution, hereafter referred to as "the solution".
This solution is to allow all nodes in the mobile network to be
reachable via permanent IP addresses, as well as maintain ongoing
sessions as the MR changes its point of attachment to the Internet
topology. This is to be done by maintaining a bidirectional tunnel
between a MR and its Home Agent.
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For doing so, the NEMO Working Group has decided to investigate
reusing the existing Mobile IPv6 [1] mechanisms for the tunnel
management, or extend it if deemed necessary.
The list of requirements below have been placed on the NEMO Basic
Support solution. They have been mostly met by the resulting
specification which can now be found in [2].
R01: The solution MUST be implemented at the IP layer level.
R02: The solution MUST set up a bi-directional tunnel between a
Mobile Router and its Home Agent (MRHA tunnel)
R03: All traffic exchanged between a MNN and a CN in the global
Internet MUST transit through the bidirectional MRHA tunnel.
R04: MNNs MUST be reachable at a permanent IP address and name.
R05: The solution MUST maintain continuous sessions (both unicast
and multicast) between MNNs and arbitrary CNs after IP handover of
(one of) the MR.
R06: The solution MUST not require modifications to any node other
than MRs and HAs.
R07: The solution MUST support fixed nodes, mobile hosts and
mobile routers in the mobile network.
R08: The solution MUST allow MIPv6-enabled MNNs to use a mobile
network link as either a home link or a foreign link.
R09: The solution MUST ensure backward compatibility with other
standards defined by the IETF. This include particularly:
R09:1: The solution MUST not prevent the proper operation of
Mobile IPv6 (i.e. the solution MUST allow MIPv6-enabled MNNs
to operate either the CN, HA, or MN operations defined in [1])
R10: The solution MUST treat all the potential configurations the
same way (whatever the number of subnets, MNNs, nested levels of
MRs, egress interfaces, ...)
R11: The solution MUST support at least 2 levels of nested mobile
networks, while, in principle, arbitrary levels of recursive
mobile networks SHOULD be supported.
R12: The solution MUST function for multihomed MR and multihomed
mobile networks as defined in [4].
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R13: NEMO Support signaling over the bidirectional MUST be
minimized
R14: Signaling messages between the HA and the MR MUST be secured:
R14.1: The receiver MUST be able to authenticate the sender
R14.2: The function performed by the sender MUST be authorized
for the content carried
R14.3: Anti-replay MUST be provided
R14.4: The signaling messages MAY be encrypted
R15: The solution MUST ensure transparent continuation of routing
and management operations over the bi-directional tunnel (this
includes e.g. unicast and multicast routing protocols, router
renumbering, DHCPv6, etc)
R16: The solution MUST not impact on the routing fabric neither on
the Internet addressing architecture. [ACCORDING TO IETF56
minutes, SHOULD BE REMOVED]
R18: The solution MAY preserve sessions established through
another egress interface when one fails
5. Changes Between Versions
5.1 Changes between version -02 and -03
- Mostly cosmetic changes
- Merged section Terminology into Introduction
- Cross-references with other NEMO WG docs
- Changed the introducion of section Section 4 and added reference to
NEMO Basic Support's resulting specification.
5.2 Changes Between Version -01 and -02
- removed sub-items in R12 (sub-cases are contained into the
definition of multihoming)
- minor typos
- R15: Added "multicast"
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- R14.4: SHOULD softened to MAY according to discussion at IETF56th
meeting.
- R17 moved to R09 and contains former R09 as a sub-case.
- R18: relaxed from "SHOULD" to may based on Vijay Devarapalli
comment (030718)
5.3 Changes Between Version -00 and -01
- title of documents: included the word "goals"
- entire document: some rewording
- section 4: changed title of section to "NEMO Design Goals".
- section 4: removed "MUST" and "MAY"
- section 4: more text about location privacy
- section 4: changed "Administration" paragraph to "Local and Global
Mobility". Text enhanced.
- section 5: R02: replace "between MR and MR's HA" with "a MR and its
HA" R11: specified at least 2 levels R12: replaced "support" with
"function" and add "multihomed MR" R13.x renumbered to R12.x since
part of R12 (editing mistake) R13 and R18: new requirements proposed
by editor and minor changes in the formulation of other Requirements
6. Acknowledgments
The material presented in this document takes most of its text from
discussions and previous documents submitted to the NEMO working
group. This includes initial contributions from Motorola, INRIA,
Ericsson and Nokia. We are particularly grateful to Hesham Soliman
(Ericsson) and the IETF ADs (Erik Nordmark and Thomas Narten) who
highly helped to set up the NEMO working group. We are also grateful
to all the following people whose comments highly contributed to the
present document: TJ Kniveton (Nokia), Alexandru Petrescu (Motorola),
Christophe Janneteau (Motorola), Pascal Thubert (CISCO), Hong-Yon
Lach (Motorola), Mattias Petterson (Ericsson) and all the others
people who have expressed their opinions on the NEMO (formely MONET)
mailing list. Thierry Ernst wish to personally grant support to its
previous employers, INRIA, and Motorola for their support and
direction in bringing this topic up to the IETF, particularly Claude
Castelluccia (INRIA) and Hong-Yon Lach (Motorola).
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7 References
[1] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[2] Devarapalli, V., "Network Mobility (NEMO) Basic Support
Protocol", draft-ietf-nemo-basic-support-03 (work in progress),
June 2004.
[3] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC
3753, June 2004.
[4] Ernst, T. and H. Lach, "Network Mobility Support Terminology",
draft-ietf-nemo-terminology-02 (work in progress), October 2004.
[5] Ng, C-W., Paik, E-K. and T. Ernst, "Analysis of Multihoming in
Network Mobility Support", draft-ietf-nemo-multihoming-issues-01
(work in progress), October 2004.
[6] Thubert, P., Wakikawa, R. and V. Devarapalli, "NEMO Home Network
Models", draft-ietf-nemo-home-network-models-01 (work in
progress), October 2004.
[7] Deering, S. and R. Hinden, "Internet Protocol Version 6 (IPv6)",
IETF RFC 2460, December 1998.
Author's Address
Thierry Ernst
WIDE at Keio University
Jun Murai Lab., Keio University.
K-square Town Campus, 1488-8 Ogura, Saiwa-Ku
Kawasaki, Kanagawa 212-0054
Japan
Phone: +81-44-580-1600
Fax: +81-44-580-1437
EMail: ernst@sfc.wide.ad.jp
URI: http://www.sfc.wide.ad.jp/~ernst/
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