Network Working Group M. Nakhjiri, Ed.
Internet-Draft Huawei USA
Intended status: Informational K. Chowdhury
Expires: January 21, 2008 Starent Networks
A. Lior
Bridgewater Systems
K. Leung
Cisco Systems
July 20, 2007
Mobile IPv4 RADIUS requirements
draft-ietf-mip4-radius-requirements-04.txt
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Copyright (C) The IETF Trust (2007).
Abstract
This document provides an applicability statement as well as a scope
definition for specifying RADIUS extensions to support Mobile IPv4.
The goal is to allow specification of RADIUS attributes to assist the
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Mobile IPv4 signaling procedures.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . . . 4
3.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Non-Goals . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
To kick start the Mobile IPv4 [RFC3344] processing of its packets by
Mobile IP agents, a mobile node (MN) needs to be able to acquire a
pair of home and care of addresses (HoA and CoA, respectively), find
a willing agent to act as a Home Agent, HA, for the MN and perform a
registration process with the HA. The registration process consists
of an exchange of a registration request and reply message between
the MN and the HA. The specification in [RFC3344] allows an MN to
start the registration process prior to having acquired its home
address or the address of its HA. Acquiring those parameters by the
MN is typically part of a process referred to as bootstrapping.
Successful processing of registration requests, and replies among
other things depends on successful creation and verification of a
number of authentication extensions developed specifically to protect
the integrity and security of the registration requests and replies
and the entities processing them, i.e. MN, HA and some times,
foreign agents, FA [RFC3344]. Creation as well as verification of
these extensions requires existence of trust relationships and shared
keys between MN and each of the mobility agents. However, creation
of these trust relationships, typically referred to as mobility
security associations, MSA, is considered outside scope of the base
Mobile IPv4 specification defined in [RFC3344]. It is desired to
avoid the scalability issues arising from creating static security
associations between an MN and all possible mobility agents. Thus it
is preferred to establish the associations dynamically using the pre-
existing relationship between the MN and the AAA server.
To allow for utilization of an existing AAA infrastructure in the
bootstrapping of the Mobile IPv4 parameters and security
relationships, the Mobile IPv4 working group has developed extensions
to allow the MN to authenticate to the home AAA server [RFC4721] and
to request assistance from the AAA server in creation of security
associations [RFC3957] with the mobility agents, all based on the
pre-established trust relationship between the MN and its home AAA
server.
However, utilization of the AAA infrastructure for Mobile IPv4
purposes, involves both Mobile IP and AAA signaling, where the
interaction between the MN and the mobility agents (HA and FA) is
based on Mobile IP signaling, while the signaling beyond the mobility
agents to the AAA server is based on AAA protocols. Around the same
time, when the specification was being developed, the AAA community
was in the process of designing Diameter as a successor to RADIUS.
Thus, the Mobile IP group developed a set of guidelines and
requirements specifically from Mobile IP standpoint [RFC2977] for
such a successor. These requirements, led to development of an
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specification for use of Diameter in Mobile IPv4 bootstrapping
[RFC4004], while the requirement document is essentially standardized
[RFC2977] after standardization of RADIUS [RFC2865]
Thus it is obvious that RADIUS does not and cannot meet all the
requirements listed In [RFC2977] without undergoing an extensive
design change and thus no RADIUS attributes have been standardized
for Mobile IP support thus far. However, in the absence of IETF
standardized RADIUS attributes for support of MIPv4, different
wireless SDOs have taken the path of developing VSAs for dynamic
bootstrapping of Mobile IPv4 registration procedure. The use of
different VSAs and different RADIUS procedures for the same purpose
of Mobile IPv4 bootstrapping at different SDOs will cause a lack
interoperability between these wireless standards, potentially
hindering mobility across these wireless networks.
To respond to the described issue, it is desired to standardize a set
of RADIUS attributes within IETF to allow a consistent and
interoperable interaction with RADIUS based AAA infrastructure during
the Mobile IPv4 Registration procedure. The bootstrapping attributes
can include configuration parameters as well as material used for
provisioning security of Mobile IPv4 messaging (authentication) as
defined by [RFC4721] and [RFC3957].
Given that RADIUS as it stands today cannot meet all the requirements
in [RFC2977], the purpose of this requirement is to define a set of
goals and nongoals specifically defined for RADIUS when it comes to
assisting mobile nodes and mobility agents in bootstrapping Mobile
IPv4 operation.
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 [RFC2119].
3. Goals and Non-Goals
Since this document serves as requirement specification for RADIUS
extensions supporting Mobile IPv4 interaction with RADIUS
infrastructure, the goals and non-goals refer to only those RADIUS
extensions that are required for support of Mobile IPv4.
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3.1. Goals
The scope of the work is to standardize RADIUS attributes and to
define the procedure by which the Mobile IPv4 agents, e.g. Home
agent (HA) and Foreign Agent (FA) map the Mobile IP registration
message fields into the proposed RADIUS attributes and vice versa.
o It is required of the RADIUS servers to be able to understand and
process the attributes to be defined for Mobile IPv4 support and
to perform verification of authentication extensions specified in
[RFC4721]. RADIUS proxies are expected to be able to forward
messages including the Mobile IPv4 related attributes as they
would with any other RADIUS messages and attributes.
o All RADIUS work MUST be backward compatible with existing RADIUS
RFCs, including RFCs as follows: [RFC2865], [RFC2866], [RFC2867],
[RFC2868], [RFC2869], [RFC3576], [RFC3579], and [RFC3580].
o It is also required of the Mobile IP agents (FA and HA) to operate
as RADIUS clients (NASes in context of [RFC2865]) when translating
RADIUS signaling into Mobile IP signaling and vice versa. Details
on the behavior of Mobile IP agents as RADIUS clients are to be
provided by the solution draft describing the RADIUS extensions
for Mobile IP support.
3.2. Non-Goals
The scope of this work is to only standardize RADIUS attributes and
to define the procedure by which the Mobile IPv4 agents, e.g. Home
agent (HA) and Foreign Agent (FA) map the Mobile IP registration
message fields into the proposed RADIUS attributes and vice versa.
It is not the intention to extend the functionality of existing
RADIUS servers or protocol. More specifically, the following are
NON-GOALS:
o Enhancing RADIUS Security: Creating new security properties for
RADIUS, such as creating key transport capabilities is not the
goal. No new security mechanisms are to be defined for the
transport of RADIUS Access Requests in relation to support of
Mobile IPv4 bootstrapping. Existing RADIUS authentication
procedures, e.g. Message-Authenticator (80) described in
[RFC2869], are used. The security considerations for use of
RADIUS in bootstrapping Mobile IPv4 are described in a later
section of this document.
o Enhancing RADIUS transport reliability: Transport properties of
RADIUS remain intact. No new reliability mechanisms are defined
in the transport of such Access Requests.
o Extending RADIUS message set: RADIUS extensions for bootstrapping
Mobile IPv4 are not to define new RADIUS messages. Diameter
Mobile IP application [RFC4004] has defined new command codes for
support of Mobile IP signaling, depending on whether Diameter
server is dealing with a Mobile IP HA or an FA. RADIUS currently
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does not have any messages that correspond to these Diameter
commands. Instead, RADIUS extensions for Mobile IPv4
bootstrapping need to provide proposals for new RADIUS attributes
that facilitates Diameter-RADIUS messaging translation without
defining any new RADIUS messaging. At the same time, the RADIUS
extensions for Mobile IPv4 need to re-use Diameter AVPs to the
fullest extent possible.
o RFC2977 compatibility: Extending RADIUS in a way that fulfills the
full list of requirements in [RFC2977] will not be attempted.
4. Attributes
A specification of the RADIUS extensions for Mobile IPv4 needs to
describe the full set of attributes required for RADIUS-Mobile IP
interaction. While some of the attributes may already be
standardized, others will require standardization and IANA type
assignments.
5. IANA Considerations
This requirement document does not allocate any numbers, so there are
no IANA considerations. On the other hand, solution documentations
for RADIUS support of Mobile IPv4 will likely introduce new RADIUS
attributes. Thus those documents will need new attribute type
numbers assigned by IANA.
6. Security considerations
Enhancing security properties of RADIUS are a specific non-goal for
the RADIUS extensions providing support for Mobile IP. Also, as this
is a requirement document and not a solution specification document,
no new security considerations aside from those that already exist
for RADIUS are noted. As such, the existing RADIUS security
considerations described previously apply, and no additional security
considerations are added here. For instance, the assumption in
RADIUS is that intermediary nodes are trusted, while at the same time
there is a concern on using AAA protocols that use hop by hop
security to distribute keys. Use of hop by hop security for key
distribution can be in conflict with some of the requirements stated
in [housley-aaa-key-mgmt], such as the requirement on binding a key
to its context and the requirement on limitation of the key scope.
The former for instance states that a key Must be bound to the
parties that are expected to have access to the keying material,
while the latter implies that parties that do not require access to a
key to perform their role MUST not have access to the key. Both of
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these requirements rule against trusting intermediary nodes and
proxies with distribution of keys. Due to lack of end to end
security mechanisms for RADIUS, imposing a MUST requirement for not
trusting proxies is not possible. RADIUS extension working group is
in the process of specifying procedures for wrapping key materials
within RADIUS attributes. For the time being, support of Mobile IP
within RADIUS may need to be based on trust of intermediaries,
despite the security considerations described.
When it comes to protecting attributes in Access Request, [RFC2868]
section 3.5 provides a mechanism for encrypting RADIUS attributes,
such as passwords. There is also work under progress for specifying
wrapping of sensitive attributes, such as key material within RADIUS
Access Accept messages. This work is currently considered as part of
RADIUS crypto-agility extensions and when completed can be used in
the process of distributing sensitive attributes, such as keying
material from RADIUS servers.
It is also possible to protect RADIUS transactions using IPsec (e.g.
as in RFC3579).
7. Acknowledgements
The authors would like to thank Alan DeKok for review and feedback,
Pete McCann and Jari Arkko for diligent shepherding of this document.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC2865] Rigney, C., "Remote Authentication Dial In User Service",
June 2000.
[RFC2866] Rigney, C., "RADIUS Accounting", June 2000.
[RFC2867] Zorn, G., "Remote Accounting Modification for Tunnel
Protocol Support", June 2000.
[RFC2977] Glass, S. and Perkins, "Mobile IP Authentication,
Authorization, and Accounting Requirements", October 2000.
[RFC3344] Perkins, C., "IP Mobility Support", August 2002.
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[RFC3957] Perkins, C. and P. Calhoun, "AAA Registration Keys for
Mobile IP", March 2005.
[RFC4004] Calhoun, P. and C. Perkins, "Diameter Mobile IP
application", May 2004.
[RFC4721] Perkins, C. and P. Calhoun, "Mobile IP Challenge/Response
Extensions (Revised)", January 2007.
[housley-aaa-key-mgmt]
Housley, R., "Guidance for AAA key management",
draft-housley-aaa-key-mgmt-09 (work in progress).
8.2. Informative References
[RFC2868] Zorn, G., "RADIUS Attributes for Tunnel Protocol Support",
June 2000.
[RFC2869] Rigney, C., "RADIUS Extensions", June 2000.
[RFC3576] Chiba, M., "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", July 2003.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", September 2003.
[RFC3580] Cogdon, P., "IEEE 802.1X Remote Authentication Dial In
User Service (RADIUS) Usage Guidelines", September 2003.
Authors' Addresses
Madjid Nakhjiri (editor)
Huawei USA
Email: mnakhjiri@huawei.com
Kuntal Chowdhury
Starent Networks
Email: kchowdhury@starentnetworks.com
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Avi Lior
Bridgewater Systems
Email: avi@bridgewatersystems.com
Kent Leung
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
US
Email: kleung@cisco.com
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