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 draft-ietf-v6ops-ipv6-only-02.txt   draft-ietf-v6ops-ipv6-only-03.txt 
v6ops J. Palet Martinez v6ops J. Palet Martinez
Internet-Draft The IPv6 Company Internet-Draft The IPv6 Company
Intended status: Informational 11 September 2026 Intended status: Informational 25 September 2026
Expires: 15 March 2027 Expires: 29 March 2027
IPv6-Only and IPv6-Mostly Terminology Definitions IPv6-Only and IPv6-Mostly Terminology Definitions
draft-ietf-v6ops-ipv6-only-02 draft-ietf-v6ops-ipv6-only-03
Abstract Abstract
This document defines the terminology regarding the usage of This document defines the terminology regarding the usage of
expressions such as "IPv6-Only" and "IPv6-Mostly", in order to avoid expressions such as "IPv6-Only" and "IPv6-Mostly", in order to avoid
confusions when using them in IETF and other documents. The goal is confusions when using them in IETF and other documents. The goal is
that a reference to "IPv6-Only" describes the actual functionality that a reference to "IPv6-Only" describes the actual functionality
being used in a given scope, not the installed protocol support. being used in a given scope, not the installed protocol support.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 15 March 2027. This Internet-Draft will expire on 29 March 2027.
Copyright Notice Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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11.4. IPv6-Mostly Segment with Dual-Stack Access Link . . . . 9 11.4. IPv6-Mostly Segment with Dual-Stack Access Link . . . . 9
11.5. IPv6-Only Segment with Dual-Stack Access Link . . . . . 11 11.5. IPv6-Only Segment with Dual-Stack Access Link . . . . . 11
11.6. IPv6-Only-Strict . . . . . . . . . . . . . . . . . . . . 12 11.6. IPv6-Only-Strict . . . . . . . . . . . . . . . . . . . . 12
12. Usage examples and practical applicability . . . . . . . . . 13 12. Usage examples and practical applicability . . . . . . . . . 13
13. Security Considerations . . . . . . . . . . . . . . . . . . . 14 13. Security Considerations . . . . . . . . . . . . . . . . . . . 14
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
16.1. Normative References . . . . . . . . . . . . . . . . . . 14 16.1. Normative References . . . . . . . . . . . . . . . . . . 14
16.2. Informative References . . . . . . . . . . . . . . . . . 15 16.2. Informative References . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
Due to the nature of the Internet and the different types of users, 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 parts of a network, providers, flows, etc., there is not a single and
easy way to categorically say something such as "IPv6-Only". easy way to categorically say something such as "IPv6-Only".
The goal of this document is to depict this situation and agree in a 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 common language to be used for IETF and other documents, in order to
facilitate ourselves and future readers, the correct understanding of facilitate ourselves and future readers, the correct understanding of
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devices, may be IPv6-Only; this is very common in Matter/Thread stub- devices, may be IPv6-Only; this is very common in Matter/Thread stub-
networks. networks.
However, the "end-networks", in general, need to continue supporting However, the "end-networks", in general, need to continue supporting
IPv4, as there are many devices or apps, in both corporate and end- 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 user networks (smartTV, IP cameras, etc.), which are IPv4-only and it
is not always feasible to update or replace them. Also, if customer 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 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 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 deployed unless it is done in such way that some transition mechanism
solves that problem as well (example an IPv6-Only Data Center, solves that problem as well (example an IPv6-Only Data Centre,
requires SIIT-DC [RFC7755]). requires SIIT-DC [RFC7755]).
In IPv6-Only access networks, IPv4 support may be provided by In IPv6-Only access networks, IPv4 support may be provided by
mechanisms that allow "IPv4-as-a-Service" (IPv4aaS, for example by mechanisms that allow "IPv4-as-a-Service" (IPv4aaS, for example by
means of encapsulation and/or translation on top of IPv6). means of encapsulation and/or translation on top of IPv6).
In should be noticed that also server segments are transitioning to In should be noticed that also server segments are transitioning to
IPv6-Only, in enterprise networks, both for servicing internal and IPv6-Only, in enterprise networks, both for servicing internal and
external clients. In this case, to support IPv4-Only clients, external clients. In this case, to support IPv4-Only clients,
multiple tools are available, such as stateless NAT64 with EAM multiple tools are available, such as stateless NAT64 with EAM
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In the case of IPv6-Only scopes, it is common that, to ensure that In the case of IPv6-Only scopes, it is common that, to ensure that
communications with legacy IPv4-Only scopes are possible, IPv4 may be communications with legacy IPv4-Only scopes are possible, IPv4 may be
transported on top of IPv6, typically by means of encapsulation or transported on top of IPv6, typically by means of encapsulation or
translation. This can be made explicit by adding "IPv4aaS" (IPv4 as translation. This can be made explicit by adding "IPv4aaS" (IPv4 as
a Service). For example, IPv6-Only with IPv4aaS access network. a Service). For example, IPv6-Only with IPv4aaS access network.
8. IPv6-Mostly (with/without DNS64) 8. IPv6-Mostly (with/without DNS64)
"IPv6-Mostly" is similar to Dual-Stack, with two additional key "IPv6-Mostly" is similar to Dual-Stack, with two additional key
elements: a NAT64 ([RFC6146]) and DHCPv4 infrastructure operating elements that allow a host to act as IPv6-Only
Option 108 ([RFC8925]). Optionally, there may be also a DNS64 ([I-D.ietf-v6ops-6mops]): a stateful NAT64 ([RFC6146]) and DHCPv4
([RFC6147]). This way, in a Dual-Stack network scope, it can support infrastructure operating Option 108 ([RFC8925]). Optionally, there
a mix of IPv4-only, Dual-Stack or IPv6-Only clients, depending on the may be also a DNS64 ([RFC6147]). This way, in a Dual-Stack network
client capabilities or configuration. It can be seen as a way to scope, it can support a mix of IPv4-only, Dual-Stack or IPv6-Only
provide IPv4 support on demand. clients, depending on the client capabilities or configuration. It
can be seen as a way to provide IPv4 support on demand.
Notes: Notes:
* there is no default interpretation regarding the DNS64 * there is no default interpretation regarding the DNS64
availability, so it is necessary to state “with" or "without availability, so it is necessary to state “with" or "without
DNS64" to explicitly qualify the case. DNS64" to explicitly qualify the case.
* when referring to a host, it should be noted that it can also have * when referring to a host, it should be noted that it should also
an embedded CLAT (464XLAT, [RFC6877]) function. have an embedded CLAT (464XLAT, [RFC6877]) function.
9. IPv6-Only-Strict 9. IPv6-Only-Strict
"IPv6-Only-Strict" in a given scope, means that only IPv6 is native "IPv6-Only-Strict" in a given scope, means that only IPv6 is native
in that scope and IPv4 is neither configured or managed, but also not in that scope and IPv4 is neither configured or managed, but also not
transported (neither encapsulated nor translated) on top of IPv6. In transported (neither encapsulated nor translated) on top of IPv6. In
other words, it means that communication with other endpoints is only other words, it means that communication with other endpoints is only
possible using IPv6. possible using IPv6.
10. Additional Scope Qualification 10. Additional Scope Qualification
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| Host | | | Host | |
| CLAT | | | CLAT | |
+------------+ - +------------+ -
Figure 3: IPv6-Only with IPv4aaS diagram Figure 3: IPv6-Only with IPv4aaS diagram
11.4. IPv6-Mostly Segment with Dual-Stack Access Link 11.4. IPv6-Mostly Segment with Dual-Stack Access Link
The following diagram shows the case of IPv6-Mostly, which may be The following diagram shows the case of IPv6-Mostly, which may be
implemented in different ways. For example, when used in implemented in different ways. For example, when used in
enterprises, the PLAT and DNS64 may be implemented in the enterprise enterprises, the PLAT (and optionally the DNS64) may be implemented
network itself, in order to gain greater control of the in the enterprise network itself, in order to gain greater control of
configuration. It is important to note that, in this case, the the configuration. It is important to note that, in this case, the
DHCPv4 function needs to support the option 108. As a result, a DHCPv4 function needs to support the option 108. As a result, a
Dual-Stack segment will be able to support both, hosts using Dual-Stack segment will be able to support both, hosts using
IPv6-Only with a CLAT function (even if they are Dual-Stack), as well IPv6-Only with a CLAT function (even if they are Dual-Stack), as well
as IPv4-Only hosts or Dual-Stack hosts without the support of CLAT/ as IPv4-Only hosts or Dual-Stack hosts without the support of CLAT/
option 108. In residential and SOHO networks, typically the PLAT is option 108. In residential and SOHO networks, typically the PLAT is
located in the service provider network, as well as the DNS64 (which located in the service provider network, as well as the DNS64. Using
is optional). Using IPv6-Mostly in that case, restricts the IPv6-Mostly in that case, restricts the communication between
communication between IPv4-Only hosts and those that are using IPv4-Only hosts and those that are using IPv6-Only mode. This is
IPv6-Only mode. This is resolved in enterprise networks by means of resolved in enterprise networks by means of an internal PLAT with EAM
an internal PLAT with EAM [RFC7757], SIIT-DC [RFC7755] or other [RFC7757], SIIT-DC [RFC7755] or other means. Residential, SOHO an
means. Residential, SOHO an enterprise networks could choose an enterprise networks could choose an IPv6-Only+IPv4aaS Access Link, so
IPv6-Only+IPv4aaS Access Link, so the case becomes a mix of them. the case becomes a mix of them.
+------------+ - +------------+ -
| ISP | | | ISP | |
| PLAT/NAT64 | | | PLAT/NAT64 | |
| DNS/DNS64 | | | DNS/DNS64 | |
+------------+ | +------------+ |
| | | |
| Dual-Stack | | Dual-Stack |
| Access Link | | Access Link |
| | | |
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upstream", "Dual-Stack BGP", "Dual-Stack router", but offers upstream", "Dual-Stack BGP", "Dual-Stack router", but offers
"IPv6-Only access". It is not common, but may be cases where it is "IPv6-Only access". It is not common, but may be cases where it is
"IPv6-Only access data-plane" and "Dual-Stack access control-plane" "IPv6-Only access data-plane" and "Dual-Stack access control-plane"
or "IPv4-only access out-of-band management". or "IPv4-only access out-of-band management".
As of this writing, most end-user networks and hosts need to support As of this writing, most end-user networks and hosts need to support
IPv4, due to many global resources being only available over IPv4. IPv4, due to many global resources being only available over IPv4.
Transition technologies may allow islands to be connected to the Transition technologies may allow islands to be connected to the
broader Internet over an IPv6-Only access networks acting as an broader Internet over an IPv6-Only access networks acting as an
underlay for legacy IPv4 traffic. An organization aiming to switch underlay for legacy IPv4 traffic. An organization aiming to switch
to an IPv6-Only end-user network will need to ensure that all host/ to an IPv6-Only end-user network will need to ensure that:
routers are capable of IPv6-Only operation and need to ensure that
all off-network resources are available over IPv6 (either as
IPv6-Only or Dual-Stack).
In the case of data-centers, "IPv6-Only compute nodes" may be * all host/routers are capable of IPv6-Only operation and,
* all off-network resources are available over IPv6 (either as
IPv6-Only or Dual-Stack).
For this reason, IPv6-Mostly seems a perfect solution to easy a
gradual move towards IPv6-Only (and IPv6-Only-Strict).
In the case of data-centres, "IPv6-Only compute nodes" may be
provided with IPv4 external IPv4 communication, using SIIT-DC. In provided with IPv4 external IPv4 communication, using SIIT-DC. In
this case, there is an "IPv6-Only data-center" when speaking about this case, there is an "IPv6-Only data-centre" when speaking about
the internal LANs (anything behind the Border Relay), but "Dual-Stack the internal LANs (anything behind the Border Relay), but "Dual-Stack
data-center upstreams". data-centre upstreams".
In the case of a mobile network, the UEs (User Equipment, e.g., In the case of a mobile network, the UEs (User Equipment, e.g.,
mobile phones) have "IPv6-Only PDP Context", those UEs may offer mobile phones) have "IPv6-Only PDP Context", those UEs may offer
"Dual-Stack Tethering" and "Dual-Stack to the UE applications"(by "Dual-Stack Tethering" and "Dual-Stack to the UE applications"(by
means of CLAT), and this is possible thanks to the support of NAT64 means of CLAT), and this is possible thanks to the support of a
in the service provider network; the NAT64 is a "Dual-Stack service", stateful NAT64 in the service provider network; the stateful NAT64 is
which has an "IPv6-Only transport to the UEs". a "Dual-Stack service", which has an "IPv6-Only transport to the
UEs".
In the case of an enterprise network, there may be a mix of VLANs or In the case of an enterprise network, there may be a mix of VLANs or
network segments offering Dual-Stack, IPv6-Only and IPv6-Mostly. So network segments offering Dual-Stack, IPv6-Only and IPv6-Mostly. So
in this case, it becomes clear by using "Dual-Stack VLAN x", in this case, it becomes clear by using "Dual-Stack VLAN x",
"IPv6-Only VLAN y" and "IPv6-Mostly VLAN z". "IPv6-Only VLAN y" and "IPv6-Mostly VLAN z".
IPv6-Only server, IPv6-Only data-center and IPv6-Only cloud IPv6-Only server, IPv6-Only data-centre and IPv6-Only cloud
environments are entirely possible as of this writing, as long as: environments are entirely possible as of this writing, as long as:
* All host/routers are capable of IPv6-Only operation. * All host/routers are capable of IPv6-Only operation.
* All accessed resources (DNS resolvers, NTP servers, software * All accessed resources (DNS resolvers, NTP servers, software
update servers, network management services, and other external update servers, network management services, and other external
resources) are available over IPv6 (either IPv6-Only or Dual- resources) are available over IPv6 (either IPv6-Only or Dual-
Stack). Stack).
* All inbound communications are capable of IPv6, either due to all * All inbound communications are capable of IPv6, either due to all
external endpoints supporting IPv6 or due to all legacy IPv4 external endpoints supporting IPv6 or due to all legacy IPv4
traffic being relayed through a gateway (such as reverse proxy, traffic being relayed through a gateway (such as reverse proxy,
SIIT-DC gateway, CDN, etc). SIIT-DC gateway, CDN, etc).
Data-centers and cloud environments may also support IPv6-Only Data-centres and cloud environments may also support IPv6-Only
subnets/interfaces and, at the same time, internal Dual-Stack in subnets/interfaces and, at the same time, internal Dual-Stack in
other subnets/interfaces, even if using non-globally reachable IPv4 other subnets/interfaces, even if using non-globally reachable IPv4
addresses, such as those listed in Section 2.2.2 of [RFC6890], which addresses, such as those listed in Section 2.2.2 of [RFC6890], which
may be also using NAT44. may be also using NAT44.
13. Security Considerations 13. Security Considerations
This document does not have any specific security considerations. This document does not have any specific security considerations.
14. IANA Considerations 14. IANA Considerations
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