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Network Working Group                                       F. JohanssonRequest for Comments: 3846                                   ipUnpluggedCategory: Standards Track                                   T. Johansson                                                              Bytemobile                                                               June 2004Mobile IPv4 Extension for Carrying Network Access IdentifiersStatus 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 Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .22.  Requirements terminology . . . . . . . . . . . . . . . . . . .23.  NAI Carrying Extension . . . . . . . . . . . . . . . . . . . .33.1.  Processing of the NAI Carrying Extension . . . . . . . .34.  HA Identity subtype  . . . . . . . . . . . . . . . . . . . . .45.  AAAH Identity subtype  . . . . . . . . . . . . . . . . . . . .46.  Security Considerations  . . . . . . . . . . . . . . . . . . .57.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .58.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .6Jhansson & Johansson        Standards Track                     [Page 1]

RFC 3846              MIPv4 Extension for AAA NAIs             June 20049.  Normative References . . . . . . . . . . . . . . . . . . . . .610. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .711. Full Copyright Statement . . . . . . . . . . . . . . . . . . .81.  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 inRFC 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 inBCP 14,RFC 2119 [1].   The Mobile IP related terminology described inRFC 3344 [5] is used   in this document.  In addition, the following terms are used:   AAAH      One of several possible AAA Servers in the Home NetworkJhansson & 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 Sections4 and5.  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 valuesJhansson & 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",RFC2486, 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 200410.  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.comJhansson & Johansson        Standards Track                     [Page 7]

RFC 3846              MIPv4 Extension for AAA NAIs             June 200411.  Full Copyright Statement   Copyright (C) The Internet Society (2004).  This document is subject   to the rights, licenses and restrictions contained inBCP 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   The IETF takes no position regarding the validity or scope of any   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 inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   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]