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Network Working Group                                       A. MatsumotoRequest for Comments: 5221                                   T. FujisakiCategory: Informational                                              NTT                                                               R. Hiromi                                                           Intec NetCore                                                             K. Kanayama                                                           INTEC Systems                                                               July 2008Requirements for Address Selection MechanismsStatus of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Abstract   There are some problematic cases when using the default address   selection mechanism thatRFC 3484 defines.  This document describes   additional requirements that operate withRFC 3484 to solve the   problems.Table of Contents1. Introduction ....................................................22. Requirements of Address Selection ...............................22.1. Effectiveness ..............................................22.2. Timing .....................................................22.3. Dynamic Behavior Update ....................................32.4. Node-Specific Behavior .....................................32.5. Application-Specific Behavior ..............................32.6. Multiple Interface .........................................32.7. Central Control ............................................32.8. Next-Hop Selection .........................................32.9. Compatibility withRFC 3493 ................................42.10. Compatibility and Interoperability withRFC 3484 ..........42.11. Security ..................................................43. Security Considerations .........................................4      3.1. List of Threats Introduced by New Address-Selection           Mechanism ..................................................4      3.2. List of Recommendations in Which Security Mechanism           Should Be Applied ..........................................54. Normative References ............................................5Matsumoto, et al.            Informational                      [Page 1]

RFC 5221                 Address-Selection Reqs                July 20081.  Introduction   Today, theRFC 3484 [RFC3484] mechanism is widely implemented in   major OSs.  However, in many sites, the default address-selection   rules are not appropriate, and cause a communication failure.  The   problem statement (PS) document [RFC5220] lists problematic cases   that resulted from incorrect address selection.   ThoughRFC 3484 made the address-selection behavior of a host   configurable, typical users cannot make use of that because of the   complexity of the mechanism and lack of knowledge about their network   topologies.  Therefore, an address-selection autoconfiguration   mechanism is necessary, especially for unmanaged hosts of typical   users.   This document contains requirements for address-selection mechanisms   that enable hosts to perform appropriate address selection   automatically.2.  Requirements of Address Selection   Address-selection mechanisms have to fulfill the following eleven   requirements.2.1.  Effectiveness   The mechanism can modifyRFC 3484 default address-selection behavior   at nodes.  As documented in the PS [RFC5220], the default rules   defined inRFC 3484 do not work properly in some environments.   Therefore, the mechanism has to be able to modify the address-   selection behavior of a host and to solve the problematic cases   described in the PS document.2.2.  Timing   Nodes can perform appropriate address selection when they select   addresses.   If nodes need to have address-selection information to perform   appropriate address selection, then the mechanism has to provide a   function for nodes to obtain the necessary information beforehand.   The mechanism should not degrade usability.  The mechanism should not   enforce long address-selection processing time upon users.   Therefore, forcing every consumer user to manipulate the address-   selection policy table is usually not an acceptable solution.  So, in   this case, some kind of autoconfiguration mechanism is desirable.Matsumoto, et al.            Informational                      [Page 2]

RFC 5221                 Address-Selection Reqs                July 20082.3.  Dynamic Behavior Update   The address-selection behavior of nodes can be dynamically updated.   When the network structure changes and the address-selection behavior   has to be changed accordingly, a network administrator can modify the   address-selection behavior of nodes.2.4.  Node-Specific Behavior   The mechanism can support node-specific address-selection behavior.   Even when multiple nodes are on the same subnet, the mechanism should   be able to provide a method for the network administrator to make   nodes behave differently.  For example, each node may have a   different set of assigned prefixes.  In such a case, the appropriate   address-selection behavior may be different.2.5.  Application-Specific Behavior   The mechanism can support application-specific address-selection   behavior or combined use with an application-specific address-   selection mechanism such as address-selection APIs.2.6.  Multiple Interface   The mechanism can support those nodes equipped with multiple   interfaces.  The mechanism has to assume that nodes have multiple   interfaces and makes address selection of those nodes work   appropriately.2.7.  Central Control   The address-selection behavior of nodes can be centrally controlled.   A site administrator or a service provider could determine or could   have an effect on the address-selection behavior at their users'   hosts.2.8.  Next-Hop Selection   The mechanism can control next-hop-selection behavior at hosts or   cooperate with other routing mechanisms, such as routing protocols   andRFC 4191 [RFC4191].  If the address-selection mechanism is used   with a routing mechanism, the two mechanisms have to be able to work   synchronously.Matsumoto, et al.            Informational                      [Page 3]

RFC 5221                 Address-Selection Reqs                July 20082.9.  Compatibility withRFC 3493   The mechanism can allow an application that uses the basic socket   interface defined inRFC 3493 [RFC3493] to work correctly.  That is,   with the basic socket interface the application can select   appropriate source and destination addresses and can communicate with   the destination host.  This requirement does not necessarily mean   that OS protocol stack and socket libraries should not be changed.2.10.  Compatibility and Interoperability withRFC 3484   The mechanism is compatible withRFC 3484.  Now thatRFC 3484 is   widely implemented, it is preferable that a new address selection   mechanism does not conflict with the address selection mechanisms   defined inRFC 3484.   If the solution mechanism changes or replaces the address-selection   mechanism defined inRFC 3484, interoperability has to be retained.   That is, a host with the new solution mechanism and a host with the   mechanism ofRFC 3484 have to be interoperable.2.11.  Security   The mechanism works without any security problems.  Possible security   threats are described in the Security Considerations section of this   document.3.  Security Considerations3.1.  List of Threats Introduced by New Address-Selection Mechanism   There will be some security incidents when combining the requirements   described inSection 2 into a protocol.  In particular, there are 3   types of threats: leakage, hijacking, and denial of service.   1.  Leakage: Malicious nodes may tap to collect the network policy       information and leak it to unauthorized parties.   2.  Hijacking: Nodes may be hijacked by malicious injection of       illegitimate policy information.RFC 3484 defines both a source       and destination selection algorithm.  An attacker able to inject       malicious policy information could redirect packets sent by a       victim node to an intentionally chosen server that would scan the       victim node activities to find vulnerable code.  Once vulnerable       code is found, the attacker can take control of the victim node.Matsumoto, et al.            Informational                      [Page 4]

RFC 5221                 Address-Selection Reqs                July 2008   3.  Denial of Service: This is an attack on the ability of nodes to       communicate in the absence of the address-selection policy.  An       attacker could launch a flooding attack on the controller to       prevent it from delivering the address selection policy       information to nodes, thus preventing those nodes from       appropriately communicating.3.2.  List of Recommendations in Which Security Mechanism Should Be      Applied   The address selection mechanism should be afforded security services   listed below.  It is preferable that these security services are   afforded via use of existing protocols (e.g., IPsec).   1.  Integrity of the network policy information itself and the       messages exchanged in the protocol.  This is a countermeasure       against leakage, hijacking, and denial of service.   2.  Authentication and authorization of parties involved in the       protocol.  This is a countermeasure against Leakage and       Hijacking.4.  Normative References   [RFC3484]  Draves, R., "Default Address Selection for Internet              Protocol version 6 (IPv6)",RFC 3484, February 2003.   [RFC3493]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.              Stevens, "Basic Socket Interface Extensions for IPv6",RFC3493, February 2003.   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and              More-Specific Routes",RFC 4191, November 2005.   [RFC5220]  Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,              "Problem Statement for Default Address Selection in              Multi-Prefix Environments: Operational Issues ofRFC 3484              Default Rules",RFC 5220, July 2008.Matsumoto, et al.            Informational                      [Page 5]

RFC 5221                 Address-Selection Reqs                July 2008Authors' Addresses   Arifumi Matsumoto   NTT PF Lab   Midori-Cho 3-9-11   Musashino-shi, Tokyo  180-8585   Japan   Phone: +81 422 59 3334   EMail: arifumi@nttv6.net   Tomohiro Fujisaki   NTT PF Lab   Midori-Cho 3-9-11   Musashino-shi, Tokyo  180-8585   Japan   Phone: +81 422 59 7351   EMail: fujisaki@nttv6.net   Ruri Hiromi   Intec Netcore, Inc.   Shinsuna 1-3-3   Koto-ku, Tokyo  136-0075   Japan   Phone: +81 3 5665 5069   EMail: hiromi@inetcore.com   Ken-ichi Kanayama   INTEC Systems Institute, Inc.   Shimoshin-machi 5-33   Toyama-shi, Toyama  930-0804   Japan   Phone: +81 76 444 8088   EMail: kanayama_kenichi@intec-si.co.jpMatsumoto, et al.            Informational                      [Page 6]

RFC 5221                 Address-Selection Reqs                July 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   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, THE IETF TRUST 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.Matsumoto, et al.            Informational                      [Page 7]