MEXT Working Group CJ. Bernardos
Internet-Draft A. de la Oliva
Intended status: Informational UC3M
Expires: September 8, 2011 F. Giust
IMDEA Networks and UC3M
March 7, 2011
A IPv6 Distributed Client Mobility Management approach using existing
mechanisms
draft-bernardos-mext-dmm-cmip-00
Abstract
The use of centralized mobility management approaches -- such as
Mobile IPv6 -- poses some difficulties to operators of current and
future networks, due to the expected large number of mobile users and
their exigent demands. All this has triggered the need for
distributed mobility management alternatives, that alleviate
operators' concerns allowing for cheaper and more efficient network
deployments.
This draft describes a possible way of achieving a distributed
mobility behavior with Client Mobile IP, based on Mobile IPv6 and the
use of Cryptographic Generated Addresses.
Status of this Memo
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Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Description of the solution . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Most of the currently standardized IP mobility solutions, like Mobile
IPv6 [RFC3775], or Proxy Mobile IPv6 [RFC5213] rely to a certain
extent on a centralized mobility anchor entity. This centralized
network node is in charge of both the control of the network entities
involved in the mobility management (i.e., it is a central point for
the control signalling), and the user data forwarding (i.e., it is
also a central point for the user plane). This makes centralized
mobility solutions prone to several problems and limitations, as
identified in [I-D.chan-distributed-mobility-ps]: longer (sub-
optimal) routing paths, scalability problems, signaling overhead (and
most likely a longer associated handover latency), more complex
network deployment, higher vulnerability due to the existence of a
potential single point of failure, and lack of granularity on the
mobility management service (i.e., mobility is offered on a per-node
basis, not being possible to define finer granularity policies, as
for example per-application).
There are basically two main approaches that are being researched
now: one aimed at making Mobile IPv6 work in a distributed way, and
another one doing the same exercise for Proxy Mobile IPv6. In this
draft we describe a solution to achieve a DMM behavior with a CMIP
(MIPv6) solution. This document is based on a research paper of the
same authors, called "Flat Access and Mobility Architecture: an IPv6
Distributed Client Mobility Management solution" [GOB+11].
2. Terminology
The following terms used in this document are defined in the Mobile
IPv6 specification [RFC3775]:
Home Agent (HA)
Home Link
Home Address (HoA)
Care-of Address (CoA)
Binding Update (BU)
Binding Acknowledgement (BA)
The following terms are defined and used in this document:
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DAR (Distributed Anchor Router). First hop routers where the mobile
nodes attach to. They also play the role of mobility managers for
the IPv6 addresses they anchor.
HDAR (Home Distributed Anchor Router). DAR which plays the role of
Home Agent for a particular IPv6 address (i.e., DAR where that
IPv6 address is anchored).
3. Description of the solution
Distributed Mobility Management approaches try to overcome the
limitations of the traditional centralized mobility management, i.e.,
Mobile IP, by bringing the mobility anchor closer to the MN.
Following this idea, in our approach -- that we call Flat Access and
Mobility Architecture (FAMA) -- the MIPv6 centralized home agent is
moved to the edge of the network, being deployed in the default
gateway of the mobile node. That is, the first elements that provide
IP connectivity to a set of MNs are also the mobility managers for
those MNs. In the following we will call these access routers
Distributed Anchor Routers (DARs).
Every time a mobile node attaches to a distributed anchor router, it
gets an IPv6 address which is topologically anchored at the DAR.
That means that while attached to this DAR, the mobile can send and
receive traffic using that address without using any tunneling nor
special packet handling. Every time the mobile node moves to a
different DAR, it gets a new IPv6 address from the new access router.
In case the MN wants to keep the reachability of the IPv6 address(es)
it obtained from the previous DAR (note that this decision is dynamic
and it is out of scope of this document, it can be done on an
application basis for example), the mobile has to involve its MIPv6
stack, by sending a Binding Update to the DAR where the IPv6 address
is anchored, using the address obtained from the current DAR as
care-of address. In this way, the IPv6 address that the node wants
to maintain plays the role of home address, and the DAR from where
that address was configured plays the role of Home Agent (for that
particular address). Note that the FAMA approach basically enables a
mobile node to simultaneously handle several IPv6 addresses -- each
of them anchored at a different DAR -- ensuring their continuous
reachability by using Mobile IPv6 in a distributed fashion (i.e.,
each access router is a potential home agent for the address it
delegates, if required). This distributed address anchoring is
enabled on demand and on a per-address granularity, which means that
depending on the user needs, it might be the case that all, some or
none of the IPv6 addresses that a mobile node configures while moving
within a FAMA domain, are kept reachable and used by the mobile.
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In traditional Mobile IPv6, the communication between the MN and the
HA is secured through IPsec [RFC4877]. Following a similar approach
in FAMA is difficult due to the large number of security associations
that would be required, since any gateway of the access network can
play the role of home agent for any mobile node. In order to
overcome this problem and provide authentication between the DAR and
the MNs, we propose the use of Cryptographically Generated Addresses
[RFC3972] (CGAs), as introduced in [I-D.laganier-mext-cga]. CGAs are
a powerful mechanism allowing authentication of the packets and
requires no public-key infrastructure, hence it is well-suited for
this application.
Following the ideas presented above, every time an MN attaches to a
DAR, it configures a CGA from a prefix anchored at the DAR (e.g., by
using stateless address auto-configuration mechanisms). This address
can then be used by the MN to establish a communication with a remote
Correspondent Node (CN) while attached to that particular DAR. If
the mobile then moves to a new DAR (nDAR), the following two cases
are possible: i) there is no need for the address that was configured
at the previous DAR (pDAR) to survive the movement: in this case
there is no further action required; ii) the mobile wants to keep the
reachability of the address configured at pDAR: in this case Mobile
IPv6 is triggered, and the MN sends a Binding Update (BU) message to
the pDAR, using the address configured at the previous DAR as home
address, and the address configured at the new DAR as care-of
address. This BU includes the CGA parameters and signature
[I-D.laganier-mext-cga], which are used by the receiving DAR to
identify the MN as the legitimate owner of the address. Although the
use of CGAs does not impose a heavy burden in terms of performance,
depending on the number of MNs handled at the DAR, the processing of
the CGAs can be problematic. To reduce the complexity of the
proposed protocol, we suggest an alternative mechanism to
authenticate any subsequent signaling packets exchanged between the
MN and the DAR (in case the mobile performs a new attachment to a
different DAR). This alternative method relies on the use of a
Permanent Home Keygen Token (PHKT), which will be used to generate
the Authorization option that the MN has to include in all next
Binding Update messages. This token is forwarded to the MN in the
Binding Acknowledgment message, sent on reply to the BU. The
procedure is depicted in Figure 1. Once the signaling procedure is
completed, a bi-directional tunnel is established between the mobile
node and the DAR where the IPv6 address is anchored (the "home" DAR
-- HDAR -- for that particular address), so the mobile can continue
using the IPv6 address.
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------ -------
| MN | | DAR |
------ -------
| |
CGA | |
config |-- BU + CGA param + signature ------>|
| | MN
PHKT |<----------------------- BA + PHKT --| auth
caching | |
| |
(first handoff)
PHKT | |
refresh,| |
next |-- BU(PHKT auth) ------------------->|
handoffs,| | MN
de-reg |<------------------------------ BA --| auth
| |
| |
(subsequent signaling)
Figure 1: Signaling between the MN and the DAR
In case the MN performs any subsequent movements and it requires to
maintain the reachability of an address for which it has already sent
a BU, the following BU messages can be secured using the PHKT
exchanged before, reducing the computational load at the receiving
DAR.
Note that on every attachment of a node to a DAR, the terminal also
obtains a new IPv6 address which is topologically anchored at that
DAR, and that this address can be used for new communications
(avoiding in this way the tunneling required when using an address
anchored at a different DAR). A mobile can keep multiple IPv6
addresses active and reachable at a given time, and that requires to
send -- every time the MN moves -- a BU message to all the previous
DARs that are anchoring the IP flows that the MN wish to maintain.
4. IANA Considerations
TBD.
5. Security Considerations
Although the approach documented in this document is attractive for
the reduced signaling overhead caused by the mobility support, it can
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be misused in some particular scenarios by malicious nodes that wish
to export an incorrect CoA in the BU message, since it does provide
proof of the MN's reachability at the visited network. Indeed, the
CGA approach assures that the BU message has been sent by the
legitimate HoA's owner but it does not make sure that same MN to be
reachable at the CoA indicated. This requires further analysis.
A possible approach to provide a more secure solution is the
following: a Return Routability procedure similar to the one defined
in MIPv6 Route Optimization can be used to mitigate the
aforementioned security issue. The Return Routability procedure
starts after the handoff. Instead of sending the BU message, the MN
sends a Care-of Test Init message (CoTI). This message is replied by
the DAR with a Care-Of Test message containing a CoA Keygen Token.
The MN can now send a BU using both Home and CoA Keygen tokens to
proof its reachability at both the HoA and the CoA. The message and
the knowledge of both tokens is a proof that the MN is the legitimate
node who has sent the BU and also is reachable at the CoA indicated.
As all security improvements, the one proposed incurs in a
performance penalty, in this case an increase in the handover delay.
Specifically this enhanced security approach requires four messages
to be exchanged between the MN and the DAR instead of the two
messages of the original solution. In terms of handover delay, it
increases it by a factor of two, as the new solution requires to two
Round Trip Times (RTTs) to conclude, instead of one.
6. Acknowledgments
The research leading to these results has received funding from the
European Community's Seventh Framework Programme (FP7-ICT-2009-5)
under grant agreement n. 258053 (MEDIEVAL project). The work of
Carlos J. Bernardos has also been partially supported by the Ministry
of Science and Innovation of Spain under the QUARTET project
(TIN2009-13992-C02-01).
7. References
7.1. Normative References
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
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IKEv2 and the Revised IPsec Architecture", RFC 4877,
April 2007.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
7.2. Informative References
[GOB+11] Giust, F., de la Oliva, A., and CJ. Bernardos, "Flat
Access and Mobility Architecture: an IPv6 Distributed
Client Mobility Management solution", 3rd IEEE
International Workshop on Mobility Management in the
Networks of the Future World (MobiWorld 2011), colocated
with IEEE INFOCOM 2011 , 2011.
[I-D.chan-distributed-mobility-ps]
Chan, A., Liu, D., Seite, P., Yokota, H., Perkins, C.,
Melia, T., Haddad, W., Demaria, E., Deng, H., and Z. Cao,
"Problem statement for distributed and dynamic mobility
management", draft-chan-distributed-mobility-ps-00 (work
in progress), October 2010.
[I-D.laganier-mext-cga]
Laganier, J., "Authorizing Mobile IPv6 Binding Update with
Cryptographically Generated Addresses",
draft-laganier-mext-cga-01 (work in progress),
October 2010.
Authors' Addresses
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
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Antonio de la Oliva
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 8803
Email: aoliva@it.uc3m.es
URI: http://www.it.uc3m.es/aoliva/
Fabio Giust
Institute IMDEA Networks and Universidad Carlos III de Madrid
Av. del Mar Mediterraneo, 22
Leganes, Madrid 28918
Spain
Email: fabio.giust@imdea.org
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