Mobile IP Working Group F. Johansson
Internet-Draft ipUnplugged
Expires: June 11, 2004 T. Johansson
Bytemobile
December 12, 2003
Mobile IPv4 Extension for carrying Network Access Identifiers
<draft-ietf-mip4-aaa-nai-02.txt>
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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 the home network has both multiple
Authentication Authorization and Accounting (AAA) servers and Home
Agents (HAs) in use, the Home AAA server may not have sufficient
information to process the re-authentication correctly (i.e., to
ensure that the same HA continues to be used). This document defines
a Mobile IP extension that carries identities for the Home AAA and HA
servers in the form of Network Access Identifiers (NAIs). The
extension allows a Home Agent to pass its identity (and that of the
Home AAA server) to the mobile node, which can then pass it on to the
local AAA server when changing its point of attachment. This
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extension may also 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 . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
Normative References . . . . . . . . . . . . . . . . . . . . . 8
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 [5]. This may unfortunately not be enough, since
some AAA infrastructures (such as Diameter [6]) use realm based
routing; such a 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 a reason for the HA to also include its own identity in the
registration reply. The MIP v4 extension defined in this document
also has a subtype defined by which this may be done. The HA identity
can then be included by the mobile node in later 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 [1].
The Mobile IP related terminology described in RFC 3344 [5] 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.
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NAI
Network Access Identifier [2].
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 [5]. The extension may be used by any node
that wants to send identity information in the form of a NAI [4].
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) [5]
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 it in a
registration reply message, provide it in every subsequent
registration request when re-authentication is needed. Failure to
re-authenticate, for instance because no AAAH can be reached, will
result in termination of the Mobile-IP session. On initiation of a
new session a new HA Identity NAI may be provided to the Mobile node,
and the requirement above will apply to the newly received NAI.
If the mobile node requires a specific home agent and it has the NAI
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 SHOULD save the latest AAAH Identity received in a
registration reply message and SHOULD provide the AAAH Identity in
every registration request sent when re-authenticating, for
efficiency reasons. Failure to reach the indicated AAAH during
re-authentication will result in a new AAAH Identity NAI being
returned (which should then be saved and provided in subsequent
registration requests). Similarly, failure to re-authenticate, for
instance because no AAAH can be reached, will result in termination
of the Mobile-IP session; on initiation of a new session a new AAAH
Identity NAI may be provided to the Mobile Node for re-use during
later re-registrations.
A foreign agent which receives the AAAH NAI by this extension in a
registration request SHOULD include the AAAH NAI provided when
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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 [4], 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
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 [3].
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 NAI Carrying Extension should be assigned a type value from both
the IANA number space for Mobile IPv4 skippable extensions, and from
the IANA number space for Mobile IPv4 advertisement extensions.
Ideally, the numbers assigned from these two numbering spaces should
have the same value.
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.
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Also thanks to Henrik Levkowetz and Kevin Purser for valuable
feedback and help when writing this draft.
Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC
2486, January 1999.
[3] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[4] Calhoun, P. and C. Perkins, "Mobile IP Network Access Identifier
Extension for IPv4", RFC 2794, March 2000.
[5] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
2002.
[6] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J. Arkko,
"Diameter Base Protocol", RFC 3588, September 2003.
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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