IPv6-only Terminology Definition
draft-palet-v6ops-ipv6-only-08

v6ops                                                  J. Palet Martinez
Internet-Draft                                          The IPv6 Company
Intended status: Informational                           21 October 2024
Expires: 24 April 2025

                    IPv6-only Terminology Definition
                     draft-palet-v6ops-ipv6-only-08

Abstract

   This document defines the terminology regarding the usage of
   expressions such as "IPv6-only", in order to avoid confusions when
   using them in IETF and other documents.  The goal is that the
   reference to "IPv6-only" describes the actual native functionality
   being used, not the actual protocol support.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Context . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IPv6-only . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IPv4-only . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Dual-stack  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Native dual-stack . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IPv6-only network . . . . . . . . . . . . . . . . . . . . . .   4
   8.  IPv6-only WAN/access  . . . . . . . . . . . . . . . . . . . .   4
   9.  IPv6-only LAN . . . . . . . . . . . . . . . . . . . . . . . .   4
   10. IPv6-only host/router . . . . . . . . . . . . . . . . . . . .   5
   11. Transitional IPv6 host/router . . . . . . . . . . . . . . . .   5
   12. IPv6-Mostly Network Segment . . . . . . . . . . . . . . . . .   5
   13. Other cases . . . . . . . . . . . . . . . . . . . . . . . . .   5
   14. IPv4 Exclusion  . . . . . . . . . . . . . . . . . . . . . . .   5
   15. Security Considerations . . . . . . . . . . . . . . . . . . .   5
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   17. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   18. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     18.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     18.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Due to the nature of the Internet and the different types of users,
   parts of a network, providers, flows, etc., there is not a single and
   easy way to categorically say something such as "IPv6-only".

   The goal of this document is to depict this situation and agree in a
   common language to be used for IETF and other documents, in order to
   facilitate ourselves and future readers, the correct understanding of
   what we are talking about.

   The term IPv6-only is being used by many IETF documents, with a clear
   definition of the scope or terminology, for example [RFC6877],
   [RFC8585] and [RFC8683].

   Note that all the references in this document are regarding the
   actual usage of IPv4/IPv6, not the support of those protocols by
   nodes.  For example, a device or access network may support both IPv4
   and IPv6, however actually is only "natively" forwarding IPv6,
   because the link used for that communication is only natively
   configured for IPv6.  IPv4 may be used as well, but it is being
   encapsulated or translated by means of IPv6.  So, from this
   perspective, this device is attached to an IPv6-only link.

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   As such, a network service is considered IPv6-only if it forwards
   IPv6, not IPv4, even if IPv4 is still supported and enabled but not
   configured neither used in the nodes participating in the service.

2.  Context

   The transition from IPv4 to IPv6 is not something that can be done,
   in the large majority of the cases, overnight and in a single step.
   Consequently, in general, we are unable to talk about a whole network
   having a "single and uniform" status regarding the IPv6 support, at
   least not in the early deployment stages of an operator network.

   Even if possible, it is not frequent to deploy new IPv6 networks
   which have no IPv4 connectivity at all, because at the current phase
   of the universal goal of the IPv6 deployment, almost every network
   still need to provide some kind of "access" to IPv4 sites.  It is not
   feasible for most of the operators to tell their customers "I can
   provide you IPv6 service, but you will not be able to access all
   Internet contents and apps, because some of them still don't support
   IPv6, so you will miss every content that it is IPv4-only".

   Some networks may have IPv6-only support for specific purposes or
   services.  For example, a DOCSIS provider may have decided that is
   worth the effort to get rid of IPv4 for the management network of the
   cable-modems.  Or a network that provides connectivity only to IoT
   devices, may be IPv6-only.

   However, the "end-networks", in general, need to continue supporting
   IPv4, as there are many devices or apps, in both corporate and end-
   user networks (smartTV, IP cameras, etc.), which are IPv4-only and it
   is not always feasible to update or replace them.  Also if customer
   devices in a LAN are IPv4-only, they will not be able to access
   IPv6-only services, so this means that IPv6-only services can't be
   deployed unless it is done in such way that some transition mechanism
   solves that problem as well (example an IPv6-only Data Center,
   requires SIIT-DC)

   In IPv6-only access networks, IPv4 support may be provided by
   mechanisms that allow "IPv4-as-a-service" (IPv4aaS, for example by
   means of encapsulation and/or translation on top of IPv6).

3.  IPv6-only

   Consequently, considering the context described in the section above,
   if we want to be precise and avoid confusing others, we can't use the
   terminology "IPv6-only" in a generic way, and we need to define what
   part of the network we are referring to.

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   From that perspective, we define the "IPv6-only" status in a given
   part(s) of a network, depending on if there is actual native
   forwarding of IPv4, so IPv4 is not configured neither managed.

4.  IPv4-only

   Similarly, we define the "IPv4-only" status in a given part(s) of a
   network, depending on if there is actual native forwarding of IPv6,
   so IPv6 is not configured neither managed.

5.  Dual-stack

   This can be applied to a host, router, link, network (part), etc.  It
   means that both, IPv4 and IPv6 are reachable, without specifying how.

6.  Native dual-stack

   This can be applied to a host, router, link, network (part), etc.  It
   means that both, IPv4 and IPv6 are configured/used natively (without
   the need of transition mechanisms).

7.  IPv6-only network

   IPv6-only can be used only if, a complete network, end-to-end, is
   actually not natively forwarding IPv4, which will mean that no-IPv4
   addresses are configured, neither used for management, neither the
   network is providing transition/translation support, neither there is
   IPv4 transit/peering.

   This is the end of the road of the IPv4-to-IPv6 transition, however
   we aren't there yet, in general at the time of writing this document,
   unless we are referring to special or disconnected (from IPv4)
   networks.

8.  IPv6-only WAN/access

   IPv6-only WAN or access can be used only if the WAN or access network
   isn't actually natively forwarding IPv4.

9.  IPv6-only LAN

   IPv6-only LAN(s) can be used only if the LAN(s), isn't actually
   natively forwarding IPv4.

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10.  IPv6-only host/router

   IPv6-only host/router can be used only if the host/router, isn't
   actually using/forwarding IPv4, so IPv4 is unconfigured and/or
   disabled in the external facing interfaces.

   Internal interfaces, such as loopback, can still be using IPv4
   (internally).

11.  Transitional IPv6 host/router

   Transitional IPv6 host/router is a dual-stack host/router with
   IPv6-only WAN where IPv4 service support is provided by means of
   transition mechanism, IPv4aaS (IPv4-as-a-service).

12.  IPv6-Mostly Network Segment

   In order to provide a more comprehesive view, we also cite here the
   IPv6-Mostly definition as can be interpreted from
   [I-D.ietf-v6ops-6mops].  An IPv6-Mostly network segment is very
   similar to a dual-stack one, with two additional key elements: a
   NAT64 ([RFC6146]) and DHCPv4 infrastructure operating Option 108
   ([RFC8925]).  This way it can support a mix of IPv4-only on-demand,
   dual-stack or IPv6-only clients, depending on the client capabilities
   or configuration.

13.  Other cases

   Similar other cases or parts of the network can be considered as
   IPv6-only if there is no actual native forwarding of IPv4 and in that
   case, after "IPv6-only" some word/short text pointing to the specific
   case or part of the network needs to be used.  For instance, we could
   talk about "IPv6-only core" if a core network is only natively
   forwarding IPv6.

14.  IPv4 Exclusion

   If an IPv6-only network or part of it, has strict filtering rules to
   avoid IPv4 to be transported on top of IPv6, this should be
   explicitly cited.  For example, and enterprise LAN, where employees
   can't use VPNs, tunnels, or even translations, could be named as
   "IPv6-only LAN with IPv4 Exclusion".

15.  Security Considerations

   This document does not have any specific security considerations.

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16.  IANA Considerations

   This document does not have any IANA considerations.

17.  Acknowledgements

   The author would like to acknowledge the inputs from Tim Chown, Noah
   Maina, Lee Howard, Azael Fernandez Alcantara, Marcos Sanz Grosson and
   Robert M.  Hinden.

18.  References

18.1.  Normative References

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <https://www.rfc-editor.org/info/rfc6146>.

   [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
              Combination of Stateful and Stateless Translation",
              RFC 6877, DOI 10.17487/RFC6877, April 2013,
              <https://www.rfc-editor.org/info/rfc6877>.

   [RFC8585]  Palet Martinez, J., Liu, H. M.-H., and M. Kawashima,
              "Requirements for IPv6 Customer Edge Routers to Support
              IPv4-as-a-Service", RFC 8585, DOI 10.17487/RFC8585, May
              2019, <https://www.rfc-editor.org/info/rfc8585>.

   [RFC8683]  Palet Martinez, J., "Additional Deployment Guidelines for
              NAT64/464XLAT in Operator and Enterprise Networks",
              RFC 8683, DOI 10.17487/RFC8683, November 2019,
              <https://www.rfc-editor.org/info/rfc8683>.

   [RFC8925]  Colitti, L., Linkova, J., Richardson, M., and T.
              Mrugalski, "IPv6-Only Preferred Option for DHCPv4",
              RFC 8925, DOI 10.17487/RFC8925, October 2020,
              <https://www.rfc-editor.org/info/rfc8925>.

18.2.  Informative References

   [I-D.ietf-v6ops-6mops]
              Buraglio, N., Caletka, O., and J. Linkova, "IPv6-Mostly
              Networks: Deployment and Operations Considerations", Work
              in Progress, Internet-Draft, draft-ietf-v6ops-6mops-00, 16
              October 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-v6ops-6mops-00>.

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Author's Address

   Jordi Palet Martinez
   The IPv6 Company
   Molino de la Navata, 75
   28420 La Navata - Galapagar Madrid
   Spain
   Email: jordi.palet@theipv6company.com
   URI:   http://www.theipv6company.com/

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