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IPv6 Multihoming without Network Address Translation
RFC 7157

Internet Engineering Task Force (IETF)                     O. Troan, Ed.
Request for Comments: 7157                                         Cisco
Category: Informational                                         D. Miles
ISSN: 2070-1721                                             Google Fiber
                                                           S. Matsushima
                                                        Softbank Telecom
                                                              T. Okimoto
                                                                NTT West
                                                                 D. Wing
                                                                   Cisco
                                                              March 2014

          IPv6 Multihoming without Network Address Translation

Abstract

   Network Address and Port Translation (NAPT) works well for conserving
   global addresses and addressing multihoming requirements because an
   IPv4 NAPT router implements three functions: source address
   selection, next-hop resolution, and (optionally) DNS resolution.  For
   IPv6 hosts, one approach could be the use of IPv6-to-IPv6 Network
   Prefix Translation (NPTv6).  However, NAT and NPTv6 should be
   avoided, if at all possible, to permit transparent end-to-end
   connectivity.  In this document, we analyze the use cases of
   multihoming.  We also describe functional requirements and possible
   solutions for multihoming without the use of NAT in IPv6 for hosts
   and small IPv6 networks that would otherwise be unable to meet
   minimum IPv6-allocation criteria.  We conclude that DHCPv6-based
   solutions are suitable to solve the multihoming issues described in
   this document, but NPTv6 may be required as an intermediate solution.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc7157.

Troan, et al.                 Informational                     [Page 1]
RFC 7157              IPv6 Multihoming without NAT            March 2014

Copyright Notice

   Copyright (c) 2014 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  IPv6 Multihomed Network Scenarios . . . . . . . . . . . . . .   6
     3.1.  Classification of Network Scenarios for Multihomed Host .   6
     3.2.  Multihomed Network Environment  . . . . . . . . . . . . .   8
     3.3.  Problem Statement . . . . . . . . . . . . . . . . . . . .   9
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.1.  End-to-End Transparency . . . . . . . . . . . . . . . . .  11
     4.2.  Scalability . . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Problem Analysis  . . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  Source Address Selection  . . . . . . . . . . . . . . . .  11
     5.2.  Next Hop Selection  . . . . . . . . . . . . . . . . . . .  12
     5.3.  DNS Recursive Name Server Selection . . . . . . . . . . .  13
   6.  Implementation Approach . . . . . . . . . . . . . . . . . . .  13
     6.1.  Source Address Selection  . . . . . . . . . . . . . . . .  14
     6.2.  Next Hop Selection  . . . . . . . . . . . . . . . . . . .  14
     6.3.  DNS Recursive Name Server Selection . . . . . . . . . . .  15
     6.4.  Other Algorithms Available in RFCs  . . . . . . . . . . .  16
   7.  Considerations for MHMP Deployment  . . . . . . . . . . . . .  16
     7.1.  Non-MHMP Host Consideration . . . . . . . . . . . . . . .  16

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