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rfc:rfc3846

Network Working Group F. Johansson Request for Comments: 3846 ipUnplugged Category: Standards Track T. Johansson

                                                            Bytemobile
                                                             June 2004
   Mobile IPv4 Extension for Carrying Network Access Identifiers

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).

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
 extension may also be used in other situations requiring
 communication of a NAI between Mobile IP nodes.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
 2.  Requirements terminology . . . . . . . . . . . . . . . . . . .  2
 3.  NAI Carrying Extension . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Processing of the NAI Carrying Extension . . . . . . . .  3
 4.  HA Identity subtype  . . . . . . . . . . . . . . . . . . . . .  4
 5.  AAAH Identity subtype  . . . . . . . . . . . . . . . . . . . .  4
 6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5
 7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
 8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  6

Jhansson & Johansson Standards Track [Page 1] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

 9.  Normative References . . . . . . . . . . . . . . . . . . . . .  6
 10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  7
 11. Full Copyright Statement . . . . . . . . . . . . . . . . . . .  8

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 to which
 HA the session was assigned.  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].  Unfortunately this may 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 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
 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 the 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 BCP 14, 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 several possible AAA Servers in the Home Network

Jhansson & Johansson Standards Track [Page 2] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

 FQDN
    Fully Qualified Domain Name.
 Identity
    The identity of a node is equal to its FQDN.
 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 Sections 4 and 5.  It is expected
 that other types of NAI will be defined by other documents in the
 future.
   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      136 (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.

Jhansson & Johansson Standards Track [Page 3] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

 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 form 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
 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.  Upon 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 form the complete FQDN
 (hostname.realm) of the home AAA server.

Jhansson & Johansson Standards Track [Page 4] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

 If several AAA servers exist 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 needs 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
 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
 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 136.  This
 extension introduces a new sub-type numbering space where the values

Jhansson & Johansson Standards Track [Page 5] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

 1 and 2 have been assigned 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 do 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 document, Mohamed M
 Khalil, Emad Qaddoura, Haseeb Akhtar, and Pat R. Calhoun.  The
 original document was removed from the MIP WG charter when no use was
 seen for the extension.  The original ideas have been reused in this
 document.  Also thanks to Henrik Levkowetz and Kevin Purser for
 valuable feedback and help when writing this document.

9. 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.

Jhansson & Johansson Standards Track [Page 6] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

10. 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

Jhansson & Johansson Standards Track [Page 7] RFC 3846 MIPv4 Extension for AAA NAIs June 2004

11. Full Copyright Statement

 Copyright (C) The Internet Society (2004).  This document is subject
 to the rights, licenses and restrictions contained in BCP 78, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

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 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
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 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
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 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Jhansson & Johansson Standards Track [Page 8]

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