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Versions: (draft-palet-ietf-v6ops-ipv6-only) 00 01 02 03 04 05

v6ops                                                  J. Palet Martinez
Internet-Draft                                         Consulintel, S.L.
Intended status: Informational                            August 3, 2017
Expires: February 4, 2018

                    IPv6-only Terminology Definition


   This document clarify the terminology regarding the usage of
   expressions such as "IPv6-only", in order to avoid confusions when
   using them in IETF and other documents, in reference to what is the
   actual functionalities being used (not the actual protocol support).

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 February 4, 2018.

Copyright Notice

   Copyright (c) 2017 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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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Context . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IPv6-only . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IPv6-only host/router . . . . . . . . . . . . . . . . . . . .   4
   5.  IPv6-only WAN/access  . . . . . . . . . . . . . . . . . . . .   4
   6.  IPv6-only LAN . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  IPv6-only core  . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Other cases . . . . . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Due to the nature of the Internet and the different types of users,
   parts of a network, providers, flows, etc., there is no 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.

   Note that all the references in this document are regarding the
   actual usage of IPv4/IPv6, not the support of those.  For example, a
   device or access network may support both IPv4 and IPv6, however
   actually is only using (forwarding at layer-2), IPv6.

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 MUST NOT talk about a whole network
   having a "single and uniform" status regarding IPv6, at least not in
   the early deployment stages.

   Even if it is 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

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   So what often happens is that some networks may have IPv6-only
   support for specific purposes.  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, despite the IETF and vendor efforts to reduce reliance on
   legacy IPv4 as soon as possible in every network or part of it, there
   are many devices, in both corporate and end-user networks (smartTV,
   IP cameras, security devices, etc.), which are IPv4-only and it is
   not feasible (since vendors may even be out of the market, or there
   is no easy way to update them with new firmware, or the vendor have
   more interest in selling new models, etc.), the "end-networks" in
   general, need to continue supporting IPv4.

   Similarly, there are situations of devices that if even they are
   dual-stack, the access network is IPv6-only, and some of the
   applications running on those devices are IPv4-only.  If those
   applications are using literal IPv4 addresses or they don't use the
   right APIs, simple translation technologies so they can use the
   IPv6-only access, may fail to work and of course, as indicated in the
   previous paragraph, it may be not possible to upgrade them.

   It is true that this IPv4 support maybe done by using tools, or sets
   of them, developed by IETF as part of the transition mechanisms
   efforts.  So, we could talk today about a situation where we can have
   "most parts" of operator (or even enterprises/organizations) networks
   being IPv6-only, however have some kind of "IPv4" support, which in
   general we are calling "IPv4-as-a-service", which means typically
   that IPv4 is transported using the IPv6 layer-3 infrastructure as an
   IPv4 layer-2 one (for example by means of encapsulation or

   Let's describe the situation in the cellular networks.  Because the
   nature of the applications in those networks, it is easier to have
   more control on how the developers work, and for example, mandate
   IPv6 support in order to allow the apps to be installed in the
   smartphones, as actually has been done by Apple.  What that means is
   that it is theoretically possible to have an IPv6-only access network
   for a complete cellular operator network.  It may be even possible
   that the core and other parts of the operator network are IPv6-only
   if all the management of those is done by means of IPv6.  However, as
   soon as any application in the smartphone requires access to
   IPv4-only end sites (example web servers), there must be some kind of
   IPv4 support in that network, for example PLAT (NAT64/DNS64) and
   consequently, some IPv4 addresses, which allow the IPv4-only traffic
   flow to end-sites by means of the upstream providers/peers.

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   Now, if those smartphones in an IPv6-only cellular network provide
   tethering (sharing of a smartphone Internet connection with other
   devices), they may also need to "transport" IPv4 (those devices may
   be IPv4-only), in a seamless way, over the IPv6-only network.

   We can extrapolate the example above to, instead of smartphones to
   LTE routers, or CEs with any wired technology (FTTH, xDSL, Cable,
   etc.).  At the end, no matter which is the access technology, we
   can't talk, in general, in the customer LANs, about IPv6-only,
   because today is very common that we must provide still some sort of
   IPv4 support ("IPv4-as-a-service").

   Consequently, if we want to be precise and avoid confusing others, we
   MUST NOT use the terminology "IPv6-only" in a generic way, and we
   need to define what part of the network we are referring to.

   From that perspective, we define the "IPv6-only" status depending on
   if there is actual layer-2 forwarding of IPv4.

3.  IPv6-only

   IPv6-only MUST be used only if, a complete network, end-to-end, is
   actually not forwarding IPv4 at layer-2, 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, so in general today, when writing this document,
   is difficult to believe that this is possible in 99% of the cases,
   unless we are referring to special or disconnected (from IPv4)

4.  IPv6-only host/router

   IPv6-only host/router MUST be used only if the host or router that we
   are referring to, isn't actually forwarding IPv4 at layer-2.

5.  IPv6-only WAN/access

   IPv6-only WAN or access MUST be used only if the WAN or access
   network that we are referring to, isn't actually forwarding IPv4 at

   For example, a smartphone (UE/handset), may be using IPv6-only WAN/
   access, however, some apps on the device may be still using IPv4 by
   means of CLAT or Bump-in-the-API, so the smartphone itself is not an
   IPv6-only host.

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   A similar situation happens if the smartphone allows other devices by
   means of tethering, to transport IPv4 over the IPv6-only WAN, and it
   is the same case if we have an IPv6-only CPE, offering by means of
   CLAT, IPv4 transport in the LAN(s).

6.  IPv6-only LAN

   IPv6-only LAN (or LANs) MUST be used only if the LAN(s) that we are
   referring to, isn't actually forwarding IPv4 at layer-2.

   The router behind this LAN may be a dual-stack one, however IPv4 is
   not being forwarded at layer-2 in the interface connecting it.

7.  IPv6-only core

   IPv6-only core MUST be used only if the core network that we are
   referring to, isn't actually forwarding IPv4 at layer-2.

8.  Other cases

   Similar other cases or parts of the network MUST be considered as
   IPv6-only if there is no actual forwarding of IPv4 at layer-2 over
   them and in that case, after "IPv6-only" MUST be some word/short text
   pointing to the specific case or part of the network.

9.  Security Considerations

   This document does not have any specific security considerations.

10.  IANA Considerations

   This document does not have any IANA considerations.

11.  Acknowledgements

   The author would like to acknowledge the inputs from Tim Chown and
   Noah Maina.

Author's Address

   Jordi Palet Martinez
   Consulintel, S.L.
   Molino de la Navata, 75
   La Navata - Galapagar, Madrid  28420

   Email: jordi.palet@consulintel.es
   URI:   http://www.consulintel.es/

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