IPv6-Only-Preferred Option for DHCP
draft-link-dhc-v6only-00

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Last updated 2019-12-04
Replaced by draft-ietf-dhc-v6only
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Dynamic Host Configuration                                    L. Colitti
Internet-Draft                                                J. Linkova
Intended status: Standards Track                                  Google
Expires: June 6, 2020                                      M. Richardson
                                                               Sandelman
                                                            T. Mrugalski
                                                                     ISC
                                                        December 4, 2019

                  IPv6-Only-Preferred Option for DHCP
                        draft-link-dhc-v6only-00

Abstract

   This document specifies a DHCP option to indicate that a host
   supports an IPv6-only mode and willing to forgo obtaining a IPv4
   address if the network provides IPv6 access.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 6, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   (https://trustee.ietf.org/license-info) in effect on the date of
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Colitti, et al.           Expires June 6, 2020                  [Page 1]
Internet-Draft     IPv6-Only-Preferred Option for DHCP     December 2019

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Reasons to Signal IPv6-Only Support in DHCPv4 Packets . . . .   4
   3.  IPv6-Only Preferred Option  . . . . . . . . . . . . . . . . .   4
     3.1.  Option format . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  DHCPv4 Client Behaviour . . . . . . . . . . . . . . . . .   5
     3.3.  DHCPv4 Server Behaviour . . . . . . . . . . . . . . . . .   6
     3.4.  Configuration Variables . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   One of the biggest challenges of deploying IPv6-only LANs is that
   such networks might contain rather heterogeneous collection of end
   hosts.  Some of them are capable of operating in IPv6-only mode
   (either because the OS and all applications are IPv6-only capable or
   because the host has some form of 464XLAT [RFC6877] deployed).  At
   the same time some devices might still have IPv4 dependencies and
   need IPv4 connectivity to operate properly.  To incrementaly rollout
   IPv6-only, network operators need to provide IPv4-as-a-service when a
   host receives an IPv4 address if it needs it, while IPv6-only capable
   devices (such as modern mobile devices) are not allocated IPv4
   addresses.  Deploying separate LAN segments for IPv6-only and for
   dual-stack hosts (such as two WiFi SSIDs or two VLANs) is undesirable
   for a number of reasons, including but not limited to:

   o  Doubling number of network segments which leads to operational
      complexity and performance impact, for instance due to TCAM
      utilization increase from an increased number of ACL entries.

   o  Placing a host into correct network segment is problematic.  For
      example, in the case of 802.11 Wi-Fi the user might select the
      wrong SSID.  In the case of wired 802.1x authentication the
      authentication server might not have all information required to
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