Mobile IPv6 WG G. Giaretta
Internet-Draft I. Guardini
Expires: December 28, 2006 E. Demaria
Telecom Italia
J. Bournelle
GET/INT
R. Lopez
Univ. of Murcia
June 26, 2006
Goals for AAA-HA interface
draft-ietf-mip6-aaa-ha-goals-02
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Copyright (C) The Internet Society (2006).
Abstract
In commercial 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
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the interaction between Mobile IPv6 and the AAA infrastructure.
Integrating the AAA infrastructure offers also a solution component
for Mobile IPv6 bootstrapping in integrated and split scenarios.
This document describes various scenarios where a AAA interface for
Mobile IPv6 is actually required. Additionally, it lists design
goals and requirements for such an interface.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Bootstrapping scenarios . . . . . . . . . . . . . . . . . . . 4
4.1. Split Scenario . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Integrated Scenario . . . . . . . . . . . . . . . . . . . 5
5. Goals for the split scenario . . . . . . . . . . . . . . . . . 6
5.1. General goals . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Service Authorization . . . . . . . . . . . . . . . . . . 7
5.3. Accounting . . . . . . . . . . . . . . . . . . . . . . . . 7
5.4. Mobile Node Authentication . . . . . . . . . . . . . . . . 8
5.5. Provisioning of configuration parameters . . . . . . . . . 8
6. Goals for the Integrated scenario . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12
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1. 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 [1].
2. Introduction
Mobile IPv6 [2] was originally designed as a protocol without any
integration with the AAA infrastructure of the Mobility Service
Provider (MSP) that offers mobility service. Nonetheless, in some
environments it might be desirable to authenticate the user based on
existing credentials stored in the AAA infrastructure, to authorize
protocol operations and to enable accounting. Due to this
requirement, Mobile IPv6 might require the interaction with the AAA
infrastructure. Integrating the AAA infrastructure offers also a
solution component for Mobile IPv6 bootstrapping [3] in split [4] and
integrated [5] scenarios.
This document describes various scenarios where a AAA interface is
required. Additionally, it lists design goals and requirements for
such an interface.
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 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.
3. Motivation
Mobile IPv6 specification [2] 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 to protect Mobile IPv6 signaling (e.g.
shared keys or certificates to setup IPsec security associations).
One approach is to statically provision the necessary configuration
parameters at MNs and HAs. This solution is sub-optimal from a
deployment perspective, especially in large networks with a lot of
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users (e.g., a mobile operator network). For this reason the Mobile
IPv6 bootstrapping problem was investigated [3]. Based on the
analysed scenarios (i.e. integrated and split), two solutions were
developed. The solution for the split scenario is described in [4]
and the one for the integrated scenario can be found at [5]. A key
point behind these mechanisms is that, whenever static provisioning
is not feasible, the AAA infrastructure of the MSP 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 HA.
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 MSP, that stores users' service
profiles and credentials.
The deployment of this service model requires the availability of an
interface between the AAA infrastructure and the HA, that can be seen
as the Network Access Server (NAS) for Mobile IPv6. The core
capabilities that should be supported by this interface include
Mobile IPv6 service authorization and maintenance (e.g. asynchronous
service termination) as well as the exchange of accounting data.
This basic set of features is needed in any Mobile IPv6 bootstrapping
scenario.
There is therefore space for the definition of a general AAA-HA
communication interface capable to support the basic features
described above (e.g. authorization and accounting) as well as the
extended capabilities (e.g. transfer of configuration data) needed to
enable various dynamic Mobile IPv6 bootstrapping scenarios.
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.
4.1. Split Scenario
In the split scenario [4], there is the assumption that the mobility
service and network access service are separate. This implies that
the mobility service can be authorized by a different entity
deploying its own AAA infrastructure. The entity offering the
mobility service is called Mobility Service Provider (MSP) while the
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entity authorizing the service is the Mobility Service Authorizer
(MSA).
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, the document [4] defines a
new service resource record (SRV RR).
Then the Mobile Node performs an IKEv2 [6] exchange with the HA to
setup IPsec SAs (to protect Mobile IPv6 signaling) and to configure
its Home Address (HoA). The IKEv2 Mobile Node to Home Agent
authentication can be done using either public key signatures or the
Extensible Authentication Protocol (EAP).
If EAP is used for authentication, the operator can choose any
available EAP authentication methods. Note that even if EAP is used,
the MN authenticates the HA using public key signature based
authentication. The HA may rely on a remote EAP server. In this
case, a AAA protocol such as RADIUS EAP [7] or Diameter EAP [8] must
be used between the HA and the home EAP server. This allows a pool
of HAs to rely on the same EAP server to authenticate Mobile Nodes.
It also allows the roaming mobility case in which the Mobile Node
obtains the mobility service in a different administrative domain
(MSP != MSA).
The Mobile Node may also want to update its FQDN in the DNS with the
newly allocated Home Address. The document [4] 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 (IDii 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, the
document [4] suggests the home AAA server to be responsible of the
update. Thus the HA should send to the home AAA server the FDQN-HoA
pair through the AAA protocol. Note that the AAA exchange between
the HA and the AAA infrastructure is normally terminated before the
HA receives the Binding Update message. The reason is that the
authentication has succeeded if the Mobile Node is able to send the
BU.
4.2. Integrated Scenario
In the integrated scenario [5], the assumption is which the mobile
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user's mobility service is authorized by the same authorizer than
network access service. Basically Mobility Service Authorizer (MSA)
and the Access Service Authorizer (ASA) are the same entity. The
scenario considers two cases:
1. Mobile Node requests a home agent to its home domain (ASA/MSA).
2. Mobile Node requests a home agent to the Access Service Provider
(ASP)
In the first case, Home Agent is allocated by user's home domain. In
the second case it is allocated by user's visited domain. In both
cases, it is assumed that the AAA server in the home domain (AAAH)
authorizes both network access service and mobility service.
In this scenario, Mobile Node discovers the Home Agent Address using
DHCPv6. During network access service authentication and
authorization, AAAH also verifies if authenticating user is
authorized to use mobility service. In affirmative case, AAAH sends
to the Network Access Server (NAS) where the Mobile Node is attached,
the information about the assigned home agent. Then NAS stores that
information. To request home agent data, Mobile Node sends a DHCPv6
Information Request to the All_DHCP_Relay_Agents_and_Servers
multicast address. With this request, Mobile Node can specify if it
wants a home agent provided by the visited domain (ASP) or by the
home domain (ASA). In both cases, the NAS acts a DHCPv6 relay. When
the NAS receives DHCPv6 Information Request then it attaches home
agent information received from AAAH in a new DHC Relay Agent Option
defined in [9].
In case Mobile Node cannot acquire home agent information via DHCPv6,
it can try the default mechanism based on DNS described in [4].
After the Mobile Node has acquired 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 [4].
5. Goals for the split scenario
The motivations and scenarios illustrated for the split scenario
raise the need to define an interface between the AAAH server and the
HA. The following sections list a set of goals for this interface.
5.1. General goals
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G1.1 The AAAH server and the HA MUST be able to authenticate each
other (mutual authentication) in order to prevent the installation
of unauthorized state on the HA.
G1.2 The AAA-HA interface MUST provide integrity protection in order
to prevent any alteration of exchanged data (e.g. Mobile IPv6
configuration parameters).
G1.3 The AAA-HA interface MUST provide replay protection.
G1.4 The AAA-HA interface SHOULD provide confidentiality since it may
be used to transfer keying material (e.g. shared key generated
during EAP authentication).
G1.5 The AAA-HA interface SHOULD support inactive peer detection.
This functionality can be used by the AAAH server to maintain a
list of active HAs (e.g. useful for HA selection).
5.2. Service Authorization
G2.1 The AAA-HA interface SHOULD allow the use of Network Access
Identifier (NAI) to identify the mobile node.
G2.2 The HA SHOULD 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).
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 support pass-through EAP
authentication with the HA working as EAP authenticator operating
in pass-through mode and the AAAH server working as back-end
authentication server.
5.5. Provisioning of configuration parameters
G5.1 The HA SHOULD be able to communicate to the AAAH server the Home
Address allocated to the MN (e.g. for allowing the AAAH server to
perform DNS update on behalf of the MN).
G5.2 The AAAH SHOULD be able to indicate to the HA if the MN is
authorized to autoconfigure its Home Address.
6. Goals for the Integrated scenario
In the integrated scenario, the AAA server provides the HA
information to the NAS as part of the whole AAA operations for
network access. Next goals are considered in addition to those
described in section Section 5.
G6.1 The AAAH server MUST be able to communicate the Home-Agent
Information (Address or FQDN) to the NAS.
G6.2 The NAS SHOULD be able to notify to the AAA infrastructure that
it supports the functionalities described in [5].
7. IANA Considerations
No new message formats or services are defined in this document.
8. Security Considerations
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As stated in section 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 a feature that is strongly
recommended to be supported. However note that some suitable
interfaces may not provide end-to-end confidentiality between AAA and
HA (e.g. AAA protocols).
9. Acknowledgements
The authors would like to thank James Kempf, Alper Yegin, Vijay
Devarapalli, Basavaraj Patil, Gopal Dommety 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 authors would like to thank also the European Commission support
in the co-funding of the ENABLE project, where this work is partly
being developed.
10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
10.2. Informative References
[3] Giaretta, G. and A. Patel, "Problem Statement for bootstrapping
Mobile IPv6", draft-ietf-mip6-bootstrap-ps-05 (work in
progress), May 2006.
[4] Giaretta, G., "Mobile IPv6 bootstrapping in split scenario",
draft-ietf-mip6-bootstrapping-split-02 (work in progress),
March 2006.
[5] Chowdhury, K. and A. Yegin, "MIP6-bootstrapping via DHCPv6 for
the Integrated Scenario",
draft-ietf-mip6-bootstrapping-integrated-dhc-01 (work in
progress), June 2006.
[6] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
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[7] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial
In User Service) Support For Extensible Authentication Protocol
(EAP)", RFC 3579, September 2003.
[8] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
[9] Yegin, A., "DHCP Option for Home Agent Discovery in MIPv6",
draft-jang-dhc-haopt-02 (work in progress), March 2006.
[10] Chowdhury, K. and A. Lior, "RADIUS Attributes for Mobile IPv6
bootstrapping", draft-chowdhury-mip6-bootstrap-radius-01 (work
in progress), November 2004.
[11] Giaretta, G., "MIPv6 Authorization and Configuration based on
EAP", draft-giaretta-mip6-authorization-eap-03 (work in
progress), March 2006.
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Authors' Addresses
Gerardo Giaretta
Telecom Italia Lab
via G. Reiss Romoli, 274
TORINO, 10148
Italy
Email: gerardo.giaretta@telecomitalia.it
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
GET/INT
9 rue Charles Fourier
Evry 91011
France
Email: julien.bournelle@int-evry.fr
Rafa Marin Lopez
University of Murcia
30071 Murcia
Spain
Email: rafa@dif.um.es
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