Mobile Networks BOF T. J. Kniveton
Internet Draft Nokia
Expires: May 1, 2003 Alper E. Yegin
Informational: November 1, 2002 DoCoMo USA Labs
Problem Scope and Requirements for Network Mobility Working Group
draft-kniveton-monet-requirements-01.txt
Status of This Memo
This document is a submission by the NEMO Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the nemo@nal.motlabs.com mailing list.
Distribution of this memo is unlimited.
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Abstract
This document suggests problem scope definitions and possible domain
requirements for proposed solutions which describe how to connect
mobile routers within the scope of the Network Mobility working
group. The recommendations made in this draft result from the
discussions of the Mobile IP mailing list, the NEMO mailing list, and
past meetings of MONET and NEMO BOF sessions.
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Contents
Status of This Memo 1
Abstract 1
1. Introduction 2
2. Terms 3
3. Goals and Problem Scope 4
4. Non-goals and Excluded Scope 4
5. Protocols 5
6. Network Architecture 6
7. Security Considerations 7
8. Intellectual Property Right Considerations 7
9. Acknowledgements 7
Authors' Addresses 8
Full Copyright Statement 9
1. Introduction
This document describes problem scope boundaries and solution
requirements for enabling subnet mobility within an IP network. This
document is considered to be a contribution toward defining the
potential requirements specification work of the Network Mobility
(NEMO) working group, based on the outcomes of discussions on the
MONET/NEMO mailing list, the Mobile IP mailing list, and at past BOF
meetings of this group which occurred IETF52, IETF53, and IETF54
conferences.
The ideas presented in this work are expected to be complimented by
other efforts to define problem scope and solution requirements for
this group, which have been described in NEMO internet-drafts [9, 5].
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2. Terms
The terminology defined in Network Mobility Support in IPv6 [4], and
that of IPv6 [2] and Mobile IPv6 [6] forms the basis for discussion
about mobile networks (and the mobile routers which enable them).
One change is noted in this terminology: for the purposes of
discussing the mobile network problem domain, no distincion is made
between Visiting or Local nodes within the mobile network. Visiting
Mobile Nodes and Local Mobile Nodes are simply considered Mobile
Nodes as defined in Mobile IP, and Local Fixed Nodes are simply
considered Fixed Nodes, with their addresses allocated on the mobile
network.
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 [1].
In addition, this document uses the following terms:
Fixed Host
A host not capable moving from its home link to other
links. A fixed node is capable of sending and receiving
packets, that is, being a source or destination of
traffic, but not a forwarder of it.
Fixed Router
A router not capable of moving from its home link to
other links. A Fixed Router does not move with respect
to the mobile network, but moves with respect to the
fixed network, following the mobile network's movements,
but mobility is taken care of by a mobile router in the
same network as this fixed router.
Mobile Host
A host which communicates from the mobile network (which
may or may not be its home link), but can also enter and
leave the mobile network.
Mobile Router
A router which moves from its home link to other links.
A mobile router is capable of forwarding packets between
two or more interfaces, with one being the Internet, and
the other link being the mobile network(s) that move
with the mobile router. The mobile router must be aware
of network mobility and must handle aspects of mobility
management for the other nodes in the mobile network.
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Mobile Network
A network whose point of attachment to the Internet can
change. A mobile network is a collection of one or more
mobile routers with possibly a number of fixed and mobile
routers, and fixed and mobile nodes behind them.
3. Goals and Problem Scope
The primary goal of the NEMO work should be to support a technical
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 point of
attachment. MNNs are both fixed (keeping the same address on the
mobile network at all times), and mobile (entering and leaving the
mobile network as they roam with respect to it). Support for both
fixed and mobile MNNs is within the scope of this work.
Secondary goals of the work can be 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.
The NEMO group is part of the IETF, and as such should be motivated
by standardization work. Although mobile networks bring up many
interesting research questions, these are only within the scope
of this group insofar as they lead directly toward implementable
solutions. Any further research topics should be offered to the IRTF
Micromobility Design Team for additional review.
Security is an important consideration, 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, such as
securing route update information when a network changes points of
attachment. These can be considered, as long as they do not conflict
with the prior paragraph about research.
4. Non-goals and Excluded Scope
The following goals are excluded:
- host mobility. This is the problem domain of Mobile IP.
- administration of the network
- address assignment of hosts and links
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- network architectures
- solutions for service discovery. These should be handled by
traditional service discovery mechanisms
5. Protocols
Internet Protocol
The mobile networks we discuss are communicating using the Internet
Protocol. Due to the advantages for mobility of IP version 6, it is
desirable to spend most effort initially on an IPv6-based solution.
However, it is also important to investigate how mobile networks can
be enabled under IPv4 [8] conditions.
To address this issue, it is desirable to either create a solution
that could be utilized by both IPv6 and IPv4 with minimal (or no)
changes, or subsequently undertake steps to adapt the solution to
IPv4 or if that is not possible, create a new IPv4-based solution.
Mobile IP
The efforts of the Mobile IP working group have resulted in the
Mobile IPv4 [7] and Mobile IPv6 [6] protocols, which have already
solved the issue of host mobility. Since challenges to enabling
mobile networks are vastly reduced by this work, it is proposed that
the work in this group will adopt the methods for host mobility used
in Mobile IP, and extend them in the simplest way possible to achieve
its goals.
MONET should be able to co-exist and not interfere with other
mobility management protocols, such as Mobile IPv4, Mobile IPv6, Fast
Handovers for Mobile IPv6 [3] and Mobile IPv4.
Addressing and Configuration
This topic is central to communication within a mobile network, so
the changes to addressing models are a top concern for work within
this group.
Multicast
There is some interest in discussing implications to multicast within
the Monet scope.
Service Discovery
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It may hold true that service discovery protocols need some
modification in this type of environment, but at this point it is
generally believed that existing solutions may be able to run on top
of a mobile network without change.
6. Network Architecture
Nesting
It should be possible to create topologies within a mobile network
of smaller subnetworks, and possibly attach other mobile networks
in that topology. Although it is not fully clear how many layers
of topology must be supported, or the complexity requirements of
those nested networks, the goal is 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.
Transit Networks
For the purposes of this work, we make a distinction between Transit
Networks and Stub Networks. 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 forwarding. A stub network, on the other hand, does not serve
as a data forwarding path. Data on a stub network is destined for an
endpoint located on that network.
In order to keep minimal complexity, transit networks are outside
of the scope of this group. Effort will be applied to solving
communication for MNNs within a stub network only.
Multi-homing
Mobile network nodes can have multiple IP interfaces, therefore be
multi-homed. On each interface they can have a different role within
the scope of network mobility. A multi-homed node might have a
fixed interface which is always attached to the same network, and a
mobile interface which changes its point of attachment. Such a node
would be a fixed host on the former interface, and a mobile host on
the latter interface. A NEMO protocol must be able to handle such
multi-homing (multi-role) cases.
Route Optimization
Using overlay networks by using Mobile IP and NEMO can create
sub-optimal routing among communicating entities. Protocols can
have route optimizations to remedy this problem by enabling entities
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to communicate their locations to each other for the shortest path.
Such methods are defined for Mobile IPv4 and Mobile IPv6. Route
optimization is an aspect of efficient communication that should be
taken into consideration within NEMO.
Protocol End-points
A NEMO protocol should be used at least by home agents and mobile
routers. This is the minimum set of entities that need to implement
this protocol to enable mobile networks.
NEMO should be transparent to fixed routers and fixed hosts,
therefore no implementation on these entities is needed.
For optional route optimizations, mobile hosts and correspondent
nodes can implement protocol extensions to utilize shortest paths in
their communications.
7. Security Considerations
The protocol signaling must be secured. The receiver of the
protocol signaling must be able to verify the authenticity and the
authorization of the sender to change routing information for the
host(s)/network indicated. Unauthenticated and unauthorized nodes'
request to change routing should not be permitted by the network.
This is a very similar to the security requirement of Mobile IP.
The difference is that when this requirement is not satisfied, the
consequences would only effect a single mobile node in the case
of Mobile IP, whereas a whole subnet, of possibly unlimited size,
would be affected in the case of NEMO. As such, stronger security
mechanisms should be required by NEMO.
8. Intellectual Property Right Considerations
9. Acknowledgements
References
[1] S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. Request for Comments (Best Current Practice) 2119,
Internet Engineering Task Force, March 1997.
[2] R. Coltun, D. Ferguson, and J. Moy. OSPF for IPv6. Request for
comments (proposed standard), Internet Engineering Task Force,
December 1999.
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[3] et al. Dommety, G. Fast handovers for mobile ipv6. Internet
Draft, Internet Engineering Task Force, July 2001.
[4] et al. Ernst, T. Mobile networks support in mobile ipv6.
Internet Draft, Internet Engineering Task Force, June 2001.
[5] T. Ernst, L. Hong-Yon, and C. Castelluccia. Network mobility
support in ipv6: Problem statement and requirements. Internet
Draft, Internet Engineering Task Force, July 2001.
[6] D. Johnson and C. Perkins. Mobility support in IPv6 (work in
progress). Internet Draft, Internet Engineering Task Force,
November 1998.
[7] C. Perkins. IP Mobility Support. Request for Comments (Proposed
Standard) 2002, Internet Engineering Task Force, October 1996.
[8] J. Postel. Internet Protocol. Request for Comments (Standard)
791, Internet Engineering Task Force, September 1981.
[9] H. Soliman and M. Pettersson. Mobile networks (monet) problem
statement and scope. Internet Draft, Internet Engineering Task
Force, February 2002.
Authors' Addresses
T. J. Kniveton
Communications Systems Lab
Nokia Research Center
313 Fairchild Drive
Mountain View, California 94043
USA
Phone: +1 650 625-2025
EMail: Timothy.Kniveton@Nokia.com
Fax: +1 650 625-2502
Alper E. Yegin
DoCoMo Communications Labs USA
101 Metro Drive, Suite 300
San Jose, California 95110
USA
Phone: +1 408 451-4743
EMail: alper@docomolabs-usa.com
Fax: +1 408 573-1090
Kniveton, Yegin Expires May 1, 2003 [Page 8]
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