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Requirements for Address Selection Mechanisms
RFC 5221

Network Working Group                                       A. Matsumoto
Request for Comments: 5221                                   T. Fujisaki
Category: Informational                                              NTT
                                                               R. Hiromi
                                                           Intec NetCore
                                                             K. Kanayama
                                                           INTEC Systems
                                                               July 2008

             Requirements for Address Selection Mechanisms

Status 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 that RFC 3484 defines.  This document describes
   additional requirements that operate with RFC 3484 to solve the
   problems.

Table of Contents

   1. Introduction ....................................................2
   2. Requirements of Address Selection ...............................2
      2.1. Effectiveness ..............................................2
      2.2. Timing .....................................................2
      2.3. Dynamic Behavior Update ....................................3
      2.4. Node-Specific Behavior .....................................3
      2.5. Application-Specific Behavior ..............................3
      2.6. Multiple Interface .........................................3
      2.7. Central Control ............................................3
      2.8. Next-Hop Selection .........................................3
      2.9. Compatibility with RFC 3493 ................................4
      2.10. Compatibility and Interoperability with RFC 3484 ..........4
      2.11. Security ..................................................4
   3. 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 ..........................................5
   4. Normative References ............................................5

Matsumoto, et al.            Informational                      [Page 1]
RFC 5221                 Address-Selection Reqs                July 2008

1.  Introduction

   Today, the RFC 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.

   Though RFC 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 modify RFC 3484 default address-selection behavior
   at nodes.  As documented in the PS [RFC5220], the default rules
   defined in RFC 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 2008

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