Mobile IP Working Group F. Johansson
Internet-Draft ipUnplugged
Expires: March 1, 2004 T. Johansson
Bytemobile
September 1, 2003
AAA NAI for Mobile IPv4 Extension
draft-ietf-mobileip-aaa-nai-06
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
When a mobile node moves between two foreign networks it has to be
reauthenticated. If the home network has multiple AAA servers the
reauthentication request may not be received by the same AAAH as
previous authentication requests.
In order for the new AAAH to be able to forward the request to the
correct HA it has to know the identity of the HA. This document
defines an extension that enables the HA to pass its identity to the
mobile node which can in turn pass it to the AAA server when changing
point of attachment. This document specifies a NAI extension that
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can carry these NAIs.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements terminology . . . . . . . . . . . . . . . . . . . 3
3. AAA NAI Extension . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Processing of the AAA NAI Extension . . . . . . . . . . . . . 5
4. HA Identity subtype . . . . . . . . . . . . . . . . . . . . . 5
5. AAAH Identity subtype . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
Noramtive References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
When building networks one would like to be able to have redundancy.
In order to achieve this, one might place multiple AAA servers in one
domain. When a mobile node registers via a visited network the
authentication will be handled by one of the AAA servers in the home
domain. At a later point, when the mobile node moves to another
visited domain it again has to be authenticated. However, due to the
redundancy offered by the AAA protocol, it can not be guaranteed that
the authentication will be handled by the same AAAH server as the
previous one which can cause problems when trying to contact the HA
assigned during this session.
To solve this the home agent MUST include the AAAH NAI in the
registration reply message, sent via the AAA infrastructure, which
the mobile node then MUST include in every subsequent registration
request sent to a foreign agent when changing point of attachment.
Furthermore, the only information that is available about the home
agent in the registration request is the IP address as defined in RFC
3344 [1]. This is unfortunately not enough, since the AAA
infrastructure needs to know the FQDN identity of the home agent to
be able to correctly handle the assignment of the home agent. A
reverse DNS lookup would only disclose the identity of the Mobile IP
interface for that HA IP address, which may or may not be the same as
the AAA interface of the home agent. One way of solving this problem
would be for the home agent to include its identity in the
registration reply so that it can be included by the mobile node in
the coming registration requests when changing point of attachment.
2. Requirements 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 [5].
The Mobile IP related described in RFC 3344 [1] is used in this
document.
The Mobile IP related terminology described in RFC 3344 [1] is used
in this document. In addition, the following terms are used:
AAAH
One of possible several AAA Servers in the Home Network
FQDN
Fully Qualified Domain Name.
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Identity
The identity of a node is equal to its FQDN.
NAI
Network Access Identifier [3].
3. AAA NAI Extension
This section defines the AAA NAI Extension, which is carried in
Mobile IP Registration Request and Reply messages [1]. The extension
is used by any node that wants to inform about its identity in the
form a of a NAI [4].
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Sub-Type | NAI ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
(Type to be assigned by IANA) (skippable) [1]
Length 8-bit unsigned integer. Length of the extension, in octets,
excluding the extension Type and the extension Length
fields. This field MUST be set to 1 plus the total length
of the NAI field.
Sub-Type This field describes the type of the entity which owns the
NAI. The following subtypes are defined:
1 HA Identity NAI HA Identity (Section 4)
2 AAAH Identity NAI AAAH Identity (Section 5)
NAI Contains the NAI [3] in a string format.
3.1 Processing of the AAA NAI Extension
When a mobile node or home agent adds an AAA NAI extension to a
registration message, the extension MUST appear prior to any
authentication extensions.
In the event the foreign agent adds an AAA NAI extension to a
registration message, the extension MUST appear prior to any
authentication extensions added by the FA.
If an HA appended an AAA-NAI extension to a Registration Reply to an
MN, and does not receive the AAA-NAI extensions in subsequent
Registration Request messages from the MN, the HA can assume that the
MN does not understand the AAA-NAI extensions. In this case, the HA
SHOULD NOT append the AAA-NAI to further Registration Reply messages
to the MN.
4. HA Identity subtype
The HA identity uses subtype 1 of the AAA NAI Extension. It contains
the NAI of the AAA interface of the HA in the form hostname@realm.
Together the hostname and realm forms the complete FQDN
(hostname.realm) of the HA's AAA interface.
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The Home Agent MUST provide this in the first Registration Reply sent
to the Mobile Node destined through the AAA infrastructure. The
extension only need to be included in subsequent Registration Replies
if the same extension is included in Registration Requests received
from the same Mobile Node.
A mobile node that recieves this extension in a registration reply
message MUST provide it in every registration request when re-
authentication is needed. If the mobile node requests a specific
home agent and it has the information available it MUST provide this
extension in its initial registration request.
The foreign agent MUST provide it to the AAA server via RADIUS [2] or
other future AAA protocols where applicable.
5. AAAH Identity subtype
The AAAH identity uses subtype 2 of the AAA NAI Extension. It
contains the NAI of the home AAA server in the form hostname@realm.
Together the hostname and realm forms the complete FQDN
(hostname.realm) of the home AAA servers interface.
If there exists several AAA servers in the Home Network, the Home
Agent MUST provide this in the first Registration Reply sent to the
Mobile Node destined through the AAA infrastructure. The extension
only need to be included in subsequent Registration Replies if the
same extension is included in Registration Requests received from the
same Mobile Node.
A mobile node MUST always save the latest AAAH Identity received in
the registration reply message and MUST provide the AAAH Identity in
every registration request sent when re-authenticating.
If the AAAH identity is present, the foreign agent MUST include this
identity when requesting the Mobile Node authentication through the
AAA infrastructure, e.g. RADIUS [2] or in other future AAA protocols
where applicable.
6. Security Considerations
This specification introduces new Mobile IP extensions that are used
to carry mobility agent and AAA server identities, in the form of
Network Access Identifiers. It is assumed that the Mobile IP
messages that would carry these extensions would be authenticated in
the manner that is described in [4], or any follow-on authentication
mechanisms. Therefore, this specification does not lessen the
security of Mobile IP messages.
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It should be noted, that the identities sent in the extensions
specified herein MAY be sent in the clear over the network. However,
the authors do not envision that this information would create any
security issues.
7. IANA Considerations
The value assigned to the AAA NAI Extension should be taken from the
IANA number space for Mobile IPv4 skippable extensions.
8. Acknowledgements
Thanks to the original authors of the GNAIE draft, Mohamed M Khalil,
Emad Qaddoura, Haseeb Akhtar, Pat R. Calhoun. The original draft
was removed from the MIP WG charter when no use was seen for the
extension. The original ideas has been reused in this draft.
Also thanks to Henrik Levkowetz and Kevin Purser for valuable
feedback and help when writing this draft.
Noramtive References
[1] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
2002.
[2] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865, June
2000.
[3] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC
2486, January 1999.
[4] Calhoun, P. and C. Perkins, "Mobile IP Network Access Identifier
Extension for IPv4", RFC 2794, March 2000.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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Authors' Addresses
Fredrik Johansson
ipUnplugged AB
Arenavagen 23
Stockholm S-121 28
SWEDEN
Phone: +46 8 725 5916
EMail: fredrik@ipunplugged.com
Tony Johansson
Bytemobile Inc
2029 Stierlin Court
Mountain View, CA 94043
USA
Phone: +1 650 862 0523
EMail: tony.johansson@bytemobile.com
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