MEXT Working Group G. Giaretta
Internet-Draft Qualcomm
Intended status: Informational I. Guardini
Expires: November 3, 2008 E. Demaria
Telecom Italia
J. Bournelle
Orange Labs
R. Lopez
Univ. of Murcia
May 2, 2008
AAA Goals for Mobile IPv6
draft-ietf-mext-aaa-ha-goals-01
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Abstract
In commercial and enterprise deployments Mobile IPv6 can be a service
offered by a Mobility Services Provider (MSP). In this case all
protocol operations may need to be explicitly authorized and traced,
requiring the interaction between Mobile IPv6 and the AAA
infrastructure. Integrating the AAA infrastructure (e.g. NAS and
AAA server) offers also a solution component for Mobile IPv6
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bootstrapping. This document describes various scenarios where a AAA
interface for Mobile IPv6 is required. Additionally, it lists design
goals and requirements for such an interface.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Bootstrapping Scenarios . . . . . . . . . . . . . . . . . . . 4
4.1. Split Scenario . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Integrated Scenario . . . . . . . . . . . . . . . . . . . 5
5. Goals for AAA-HA interface . . . . . . . . . . . . . . . . . . 6
5.1. General goals . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Service Authorization . . . . . . . . . . . . . . . . . . 6
5.3. Accounting . . . . . . . . . . . . . . . . . . . . . . . . 7
5.4. Mobile Node Authentication . . . . . . . . . . . . . . . . 8
5.5. Provisioning of Configuration Parameters . . . . . . . . . 8
6. Goals for the AAA-NAS interface . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . . . 12
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1. Introduction
Mobile IPv6 [1] provides the basic IP mobility functionality for
IPv6. When Mobile IPv6 is used in tightly managed environments with
the use of the AAA (Authentication, Authorization and Accounting)
infrastructure, an interface between Mobile IPv6 and AAA protocols
needs to be defined. Also, two scenarios for bootstrapping Mobile
IPv6 service [2] , i.e., split [3] and integrated [4] scenarios,
require the specification of a message exchange between the HA and
AAA infrastructure for authentication and authorization purposes and
a message exchange between the AAA server and the NAS in order to
provide the visited network with the necessary configuration
information (e.g. Home Agent address).
This document describes various scenarios where a AAA interface is
required. Additionally, it lists design goals and requirements for
the communication between the HA and the AAA server and the NAS and
the AAA server needed in the split and integrated scenarios.
Requirements are listed in case either IPsec or rfc 4285 [5] is used
for Mobile IPv6 authentication.
This document only describes requirements, goals and scenarios. It
does not provide solutions.
Notice that this document builds on the security model of the AAA
infrastructure. As such, the end host/user shares credentials with
the home AAA server and the communication between the AAA server and
the AAA client may be protected. If the AAA server and the AAA
client are not part of the same administrative domain, then some sort
of contractual relationship between the involved administrative
domains is typically in place in form of roaming agreements.
2. Terminology
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 [6], with the
qualification that unless otherwise stated these words apply to the
design of the AAA protocol extension, not its implementation or its
usage.
Some of the terms are also extracted from [2].
o Access Service Authorizer (ASA). A network operator that
authenticates a mobile node and establishes the mobile node's
authorization to receive Internet service.
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o Access Service Provider (ASP). A network operator that provides
direct IP packet forwarding to and from the end host.
o Mobility Service Authorizer (MSA). A service provider that
authorizes Mobile IPv6 service.
o Mobility Service Provider (MSP). A service provider that provides
Mobile IPv6 service. In order to obtain such service, the mobile
node must be authenticated and prove authorization to obtain the
service.
3. Motivation
Mobile IPv6 specification [1] requires that Mobile Nodes (MNs) are
provisioned with a set of configuration parameters, namely the Home
Address and the Home Agent Address, in order to accomplish a home
registration. Moreover, MNs and Home Agents (HAs) must share the
cryptographic material needed in order to setup IPsec security
associations to protect Mobile IPv6 signaling (e.g. shared keys or
certificates). This is referred as the bootstrapping problem: as
described in [2], the AAA infrastructure can be used as the central
element to enable dynamic Mobile IPv6 bootstrapping. In this case
the AAA infrastructure can be exploited to offload the end host's
authentication to the AAA server as well as to deliver the necessary
configuration parameters to the visited network (e.g. Home Agent
address as specified in [4]).
Moreover, in case Mobile IPv6 is a service offered by a Mobility
Service Provider (MSP), all protocol operations (e.g., home
registrations) may need to be explicitly authorized and monitored
(e.g., for accounting purposes). This can be accomplished relying on
the AAA infrastructure of the MSA that stores user profiles and
credentials.
4. Bootstrapping Scenarios
This section describes some bootstrapping scenarios in which a
communication between the AAA infrastructure of the Mobility Service
Provider and the Home Agent is needed. The need of a MIPv6-aware
communication between the AAA server and the Network Access Server
(NAS) is also described. For more details, please refer to the
bootstrapping documents [2], [3] and [4].
4.1. Split Scenario
In the split scenario [3], there is the assumption that the mobility
service and network access service are not provided by the same
administrative entity. This implies that the mobility service is
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authorized by the MSA that is a different entity from the ASA.
In this scenario, the Mobile Node discovers the Home Agent Address
using the Domain Name Service (DNS). It queries the address based on
the Home Agent name or by service name. In the former case, the
Mobile Node is configured with the Fully Qualified Domain Name (FDQN)
of the Home Agent. In the latter case, [3] defines a new service
resource record (SRV RR).
Then the Mobile Node performs an IKEv2 [8] exchange with the HA to
setup IPsec SAs (to protect Mobile IPv6 signaling) and to configure
its Home Address (HoA). Mutual authentication for IKEv2 between
Mobile Node and Home Agent can be done with or without use of
Extensible Authentication Protocol (EAP).
If EAP is used for authentication, the operator can choose any
available EAP methods. Use of EAP with the AAA infrastructure allows
the HA for not necessarily maintaining authentication credentials for
each Mobile Node by itself, checking the validity of the credentials
with the AAA infrastructure. It also allows roaming in terms of
Mobile IPv6 service where MSP and MSA belong to different
administrative domains. In this case the HA in the MSP can check the
vailidity of the credentials provided by the MN with the AAA
infrastructure of MSA, receiving the relevant authorization
information.
The Mobile Node may also want to update its FQDN in the DNS with the
newly allocated Home Address. [3] recommends that the HA performs the
DNS entry update on behalf of the Mobile Node. For that purpose, the
Mobile Node indicates its FDQN in the IKEv2 exchange (IDi field in
IKE_AUTH) and adds a DNS Update Option in the Binding Update message
sent to the HA.
When the Mobile Node uses a Home Agent belonging to a different
administrative domain (MSP != MSA), the local HA may not share a
security association with the home DNS server. In this case, [3]
suggests that the home AAA server is responsible for the update.
Thus, the HA should send to the home AAA server the (FDQN, HoA) pair.
4.2. Integrated Scenario
In the integrated scenario [4], the assumption is that the Access
Service Authorizer (ASA) is same as the Mobility Service Authorizer
(MSA).
The Home Agent can the assigned either in the Access Service
Provider's network or in the separate network. In the former case,
the MSP is the same entity as the ASP, whereas in the latter case MSP
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and ASP are different entities.
In this scenario, Mobile Node discovers the Home Agent Address using
DHCPv6. If the user is authorized for Mobile IPv6 service, during
the network access authentication the AAAH sends the information
about the assigned Home Agent to the Network Access Server (NAS)
where the Mobile Node is currently attached. To request Home Agent
data, the Mobile Node sends a DHCPv6 Information Request to the
All_DHCP_Relay_Agents_and_Servers multicast address. With this
request, the Mobile Node can specify if it wants a Home Agent
provided by the visited domain (ASP/MSP) or by the home domain (ASA/
MSA). In both cases, the NAS acts a DHCPv6 relay. When the NAS
receives the DHCPv6 Information Request then it sends Home Agent
information received from AAAH in a new DHC Relay Agent Option as
defined in [4].
In case the Mobile Node cannot acquire Home Agent information via
DHCPv6, it can try the default mechanism based on DNS described in
[3]. After the Mobile Node has acquired the Home Agent information,
the mechanism used to bootstrap the HoA, IPsec Security Association,
and Authentication and Authorization with the MSA is the same
described in the bootstrapping solution for split scenario [3].
5. Goals for AAA-HA interface
Section 4 raises the need to define extensions for the AAA protocol
used between the AAA server of the MSA and the HA. The following
sections list the goals for such an interface. This communication is
needed for both split and integrated scenario.
5.1. General goals
G1.1 The communication between the AAAH server and the HA MUST reuse
existing AAA security mechanisms with regard to authentication,
replay, integrity, and confidentiality protection. These
communication security mechanisms prevent a number of classical
threats, including the alteration of exchanged data (e.g., Mobile
IPv6 configuration parameters) and the installation of
unauthorized state.
5.2. Service Authorization
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G2.1 The AAA-HA interface MUST allow the use of Network Access
Identifier (NAI) to identify the user.
G2.2 The HA MUST be able to query the AAAH server to verify Mobile
IPv6 service authorization for the mobile node.
G2.3 The AAAH server MAY assign explicit operational limitations and
authorization restrictions on the HA (e.g., packet filters, QoS
parameters).
G2.4 The AAAH server MUST be able to send an authorization lifetime
to the HA to limit Mobile IPv6 session duration for the MN.
G2.5 The HA MUST be able to request to the AAAH server an extension
of the authorization lifetime granted to the MN.
G2.6 The AAAH server MUST be able to force the HA to terminate an
active Mobile IPv6 session for authorization policy reasons (e.g.,
credit exhaustion).
G2.7 The HA MUST be able to indicate to the AAAH the IPv6 HoA that
will be assigned to the MN.
G2.8 The AAAH server MUST be able to authorize the MN to use an IPv6
HoA and MUST indicate that to the HA.
G2.9 The AAAH server MUST be able to indicate to the HA whether
return routability test (HoT, HoTi) shall be permitted or not via
the HA for a given MN.
G2.10 The AAAH server MUST be able to support different levels of
Mobile IPv6 authorization. For example, the AAAH server may
authorize the MN to use of MIPv6 (as defined in [1]) or may
authorize the MN to utilize an IPv4 HoA assigned for Dual Stack
MIPv6 [9].
G2.11 The AAAH server MUST be able to indicate to the HA whether the
bearer traffic for the MN needs to receive IPsec ESP protection.
G2.12 The HA MUST be able to authenticate the MN through the AAAH in
case a pre-share key is used in IKEv2 for user authentication.
The exact procedure is part of the solution space.
5.3. Accounting
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G3.1 The AAA-HA interface MUST support the transfer of accounting
records needed for service control and charging. These include
(but may not be limited to): time of binding cache entry creation
and deletion, octets sent and received by the mobile node in bi-
directional tunneling, etc.
5.4. Mobile Node Authentication
G4.1 The AAA-HA interface MUST allow the HA to act as a pass-through
EAP authenticator.
G4.2 The AAA - HA interface MUST support authentication based on the
Mobility Message Authentication Options defined in [5].
G4.3 The AAAH MUST be able to provide a MN-HA key (or data used for
subsequent key derivation of the MN-HA key by the HA) to the HA if
requested. Additional data, such as the SPI or lifetime
parameters, are sent along with the keying material.
G4.4 The HA SHOULD be able to request the AAAH server to
authenticate the MN with the value in the MN-AAA Mobility Message
Authentication Option.
G4.5 The HA MUST include an identifier of the mobile node in the AAA
transactions with the AAAH server.
5.5. Provisioning of Configuration Parameters
o The HA SHOULD be able to communicate to the AAAH server the Home
Address allocated to the MN and the FQDN of the MN (e.g., for
allowing the AAAH server to perform a DNS update on behalf of the
MN).
o The AAAH SHOULD be able to indicate to the HA if the MN is
authorized to autoconfigure its Home Address.
6. Goals for the AAA-NAS interface
In the integrated scenario, the AAA server provides the HA
information to the NAS as part of the whole AAA operations for
network access.
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G6.1 The AAAH server MUST be able to communicate the Home Agent
Information (IP Address or FQDN) to the NAS.
G6.2 The NAS MUST be able to notify the AAAH if it supports the AAA
extensions designed to receive the HA assignment information
described in [4].
G6.3 The ASP/MSP SHOULD be able to indicate to the MSA if it can
allocate a Home Agent to the MN. Therefore the NAS SHOULD be able
to include suggested HA address in the ASP in the NAS - AAA
interaction.
G6.4 The AAA server of the MSA MUST be able to indicate to the NAS
whether the MN is authorized to use a local Home Agent (i.e. a
Home Agent in the ASP/MSP).
G6.5 The overall AAA solution for integrated scenario MUST support
the scenario where the AAA server of the ASA/MSA used for network
access authentication is different from the AAA server used for
mobility service authentication and authorization.
7. IANA Considerations
This document does not require actions by IANA.
8. Security Considerations
As stated in Section 5.1 the AAA-HA interface must provide mutual
authentication, integrity and replay protection. Furthermore, if
security parameters (e.g., IKE pre-shared key) are transferred
through this interface, confidentiality is strongly recommended to be
supported. In this case the links between the HA and the AAA server
of the MSA and between the NAS and the AAA server MUST be secure.
9. Acknowledgements
The authors would like to thank James Kempf, Alper Yegin, Vijay
Devarapalli, Basavaraj Patil, Gopal Dommety, Marcelo Bagnulo and
Madjid Nakhjiri for their comments and feedback. Moreover the
authors would like to thank Hannes Tschofenig for his deep technical
and editorial review of the draft. Finally the aithors would like to
thank Kuntal Chowdhury who contribbuted identifying the goals related
to rfc4285 authentication.
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10. References
10.1. Normative References
[1] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[2] Patel, A. and G. Giaretta, "Problem Statement for bootstrapping
Mobile IPv6 (MIPv6)", RFC 4640, September 2006.
[3] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
Bootstrapping in Split Scenario", RFC 5026, October 2007.
[4] Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the
Integrated Scenario",
draft-ietf-mip6-bootstrapping-integrated-dhc-06 (work in
progress), April 2008.
[5] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury,
"Authentication Protocol for Mobile IPv6", RFC 4285,
January 2006.
[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[7] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury,
"Mobile Node Identifier Option for Mobile IPv6 (MIPv6)",
RFC 4283, November 2005.
10.2. Informative References
[8] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306,
December 2005.
[9] Soliman, H., "Mobile IPv6 support for dual stack Hosts and
Routers (DSMIPv6)", draft-ietf-mip6-nemo-v4traversal-06 (work in
progress), November 2007.
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Authors' Addresses
Gerardo Giaretta
Qualcomm
5775 Morehouse Drive
San Diego, 92109
USA
Email: gerardo@qualcomm.com
Ivano Guardini
Telecom Italia Lab
via G. Reiss Romoli, 274
TORINO, 10148
Italy
Email: ivano.guardini@telecomitalia.it
Elena Demaria
Telecom Italia Lab
via G. Reiss Romoli, 274
TORINO, 10148
Italy
Email: elena.demaria@telecomitalia.it
Julien Bournelle
Orange Labs
Email: julien.bournelle@gmail.com
Rafa Marin Lopez
University of Murcia
30071 Murcia
Spain
Email: rafa@dif.um.es
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