IPv6 Address Assignment to End Sites
RFC 6177

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Internet Engineering Task Force (IETF)                         T. Narten
Request for Comments: 6177                                           IBM
BCP: 157                                                       G. Huston
Obsoletes: 3177                                                    APNIC
Category: Best Current Practice                               L. Roberts
ISSN: 2070-1721                                      Stanford University
                                                              March 2011

                  IPv6 Address Assignment to End Sites

Abstract

   RFC 3177 argued that in IPv6, end sites should be assigned /48 blocks
   in most cases.  The Regional Internet Registries (RIRs) adopted that
   recommendation in 2002, but began reconsidering the policy in 2005.
   This document obsoletes the RFC 3177 recommendations on the
   assignment of IPv6 address space to end sites.  The exact choice of
   how much address space to assign end sites is an issue for the
   operational community.  The IETF's role in this case is limited to
   providing guidance on IPv6 architectural and operational
   considerations.  This document reviews the architectural and
   operational considerations of end site assignments as well as the
   motivations behind the original recommendations in RFC 3177.
   Moreover, this document clarifies that a one-size-fits-all
   recommendation of /48 is not nuanced enough for the broad range of
   end sites and is no longer recommended as a single default.

   This document obsoletes RFC 3177.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6177.

Narten, et al.            Best Current Practice                 [Page 1]
RFC 6177          IPv6 Address Assignment to End Sites        March 2011

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
   2. On /48 Assignments to End Sites .................................4
   3. Other RFC 3177 Considerations ...................................6
   4. Impact on IPv6 Standards ........................................6
      4.1. RFC 3056: Connection of IPv6 Domains via IPv4 Clouds .......6
      4.2. IPv6 Multicast Addressing ..................................7
   5. Summary .........................................................7
   6. Security Considerations .........................................8
   7. Acknowledgments .................................................8
   8. Informative References ..........................................8

Narten, et al.            Best Current Practice                 [Page 2]
RFC 6177          IPv6 Address Assignment to End Sites        March 2011

1.  Introduction

   There are a number of considerations that factor into address
   assignment policies.  For example, to provide for the long-term
   health and scalability of the public routing infrastructure, it is
   important that addresses aggregate well [ROUTE-SCALING].  Likewise,
   giving out an excessive amount of address space could result in
   premature depletion of the address space.  This document focuses on