Mobile IP Working Group F. Johansson
Internet-Draft ipUnplugged
Expires: May 31, 2004 T. Johansson
Bytemobile
December 1, 2003
Mobile IPv4 Extension for carrying Network Access Identifiers
<draft-ietf-mip4-aaa-nai-01.txt>
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This document is an Internet-Draft and is in full conformance with
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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
re-authenticated. If for instance the home network has multiple
Authentication Authorization and Accounting (AAA) servers the
re-authentication request may not be received by the same Home AAA
server as previous authentication requests. In order for the new
Home AAA server to be able to forward the request to the correct Home
Agent it has to know the identity of the Home Agent. This document
defines a Mobile IP extension that carries identities in the form of
Network Access Identifiers (NAIs), which may be used by an HA to pass
its identity to the mobile node which can then pass it on to the new
AAA server when changing point of attachment. This extension may also
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be used in other situations requiring communication of a NAI between
Mobile IP nodes.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements terminology . . . . . . . . . . . . . . . . . . . 3
3. NAI Carrying Extension . . . . . . . . . . . . . . . . . . . . 4
3.1 Processing of the NAI Carrying Extension . . . . . . . . 5
4. HA Identity subtype . . . . . . . . . . . . . . . . . . . . . 5
5. AAAH Identity subtype . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 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 result in the new AAAH not knowing which HA
the session was assigned to. This document defines a Mobile IP
extension which can be used to distribute the information needed to
resolve this.
Furthermore, the only information that is normally 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 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 have a
one-to-one correspondence with the home agent FQDN identity. This is
the reason why the HA also includes its own identity in the
registration reply. It can then 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 [4].
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.
Identity
The identity of a node is equal to its FQDN.
NAI
Network Access Identifier [2].
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3. NAI Carrying Extension
This section defines the NAI Carrying Extension which may be used in
Mobile IP Registration Request and Reply messages, and also in Mobile
IP Agent Advertisements [1]. The extension may be used by any node
that wants to send identity information in the form of a NAI [3].
This document also defines some subtype numbers which identify the
specific type of NAI carried, in Section 4 and Section 5. It is
expected that other types of NAI will be defined by other documents
in the future.
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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 particular type NAI which is
carried in the NAI field.
NAI Contains the NAI [2] in a string format.
3.1 Processing of the NAI Carrying Extension
When a mobile node or home agent adds a NAI Carrying Extension to a
registration message, the extension MUST appear prior to any
authentication extensions.
In the event the foreign agent adds a NAI Carrying Extension to a
registration message, the extension MUST appear prior to any
authentication extensions added by the FA.
If an HA has appended a NAI Carrying Extension to a Registration
Reply to an MN, and does not receive the NAI extension in subsequent
Registration Request messages from the MN, the HA can assume that the
MN does not understand this NAI extension. In this case, the HA
SHOULD NOT append this NAI extension to further Registration Reply
messages to the MN.
4. HA Identity subtype
The HA identity uses subtype 1 of the NAI Carrying Extension. It
contains the NAI of the HA in the form hostname@realm. Together the
hostname and realm forms the complete FQDN (hostname.realm) of the
HA.
A Home Agent using this extension MUST provide it in the first
Registration Reply sent to a Mobile Node which is not currently
registered. The extension only need to be included in subsequent
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Registration Replies if the same extension is included in
Registration Requests received from the same Mobile Node.
A mobile node using this extension MUST, if it receives in a
registration reply message, provide it in every subsequent
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.
A foreign agent which receives the Home Agent NAI by this extension
in a registration request SHOULD include the Home Agent NAI when
requesting Mobile Node authentication through the AAA infrastructure
if the AAA protocol used can carry the information.
5. AAAH Identity subtype
The AAAH identity uses subtype 2 of the NAI Carrying 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 server.
If there exists several AAA servers in the Home Network, a Home Agent
providing AAAH selection support according to this document MUST
provide the AAAH identity in the first Registration Reply sent to the
Mobile Node. 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 a
registration reply message and MUST provide the AAAH Identity in
every registration request sent when re-authenticating.
A foreign agent which receives the AAAH NAI by this extension in a
registration request SHOULD include the AAAH NAI provided when
requesting Mobile Node authentication through the AAA infrastructure
if the AAA protocol used can carry the information.
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. The Mobile IP messages that carry this
extension MUST be authenticated as described in [3], unless other
authentication methods have been agreed upon. Therefore, this
specification does not lessen the security of Mobile IP messages.
It should be noted that the identities sent in the extensions
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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
This document defines one new mobile IP extension, and one new Mobile
IP extension sub-type numbering space to be managed by IANA.
Section 3 defines a new Mobile IP extension, the Mobile IP NAI
Carrying Extension. The type number for this extension is [TBD,
assigned by IANA]. This extension introduces a new sub-type
numbering space where the values 1 and 2 has been assigned values in
this document. Approval of new Mobile IP NAI Carrying Extension
sub-type numbers is subject to Expert Review, and a specification is
required [5].
The content and format for this extension is not specific to AAA
NAIs, so if in the future new NAIs are defined which does not
strictly fall within the category of AAA NAIs, they may nevertheless
be accommodated within the subtype numbering space defined for the
NAI Carrying Extension defined in this document.
The value assigned to the NAI Carrying 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.
Normative References
[1] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
2002.
[2] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC
2486, January 1999.
[3] Calhoun, P. and C. Perkins, "Mobile IP Network Access Identifier
Extension for IPv4", RFC 2794, March 2000.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
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Levels", BCP 14, RFC 2119, March 1997.
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
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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