<- RFC Index (8501..8600)
RFC 8585
Internet Engineering Task Force (IETF) J. Palet Martinez
Request for Comments: 8585 The IPv6 Company
Category: Informational H. M.-H. Liu
ISSN: 2070-1721 D-Link Systems, Inc.
M. Kawashima
NEC Platforms, Ltd.
May 2019
Requirements for IPv6 Customer Edge Routers
to Support IPv4-as-a-Service
Abstract
This document specifies the IPv4 service continuity requirements for
IPv6 Customer Edge (CE) routers that are provided either by the
service provider or by vendors who sell through the retail market.
Specifically, this document extends the basic requirements for IPv6
CE routers as described in RFC 7084 to allow the provisioning of IPv6
transition services for the support of IPv4-as-a-Service (IPv4aaS) by
means of new transition mechanisms. The document only covers
IPv4aaS, i.e., transition technologies for delivering IPv4 in
IPv6-only access networks. IPv4aaS is necessary because there aren't
sufficient IPv4 addresses available for every possible customer/
device. However, devices or applications in the customer Local Area
Networks (LANs) may be IPv4-only or IPv6-only and still need to
communicate with IPv4-only services on the Internet.
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 candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8585.
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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
Provisions Relating to IETF Documents
(https://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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. LAN-Side Configuration . . . . . . . . . . . . . . . . . 5
3.2. Transition Technologies Support for IPv4 Service
Continuity (IPv4-as-a-Service) . . . . . . . . . . . . . 5
3.2.1. 464XLAT . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.2. Dual-Stack Lite (DS-Lite) . . . . . . . . . . . . . . 8
3.2.3. Lightweight 4over6 (lw4o6) . . . . . . . . . . . . . 9
3.2.4. MAP-E . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.5. MAP-T . . . . . . . . . . . . . . . . . . . . . . . . 10
4. IPv4 Multicast Support . . . . . . . . . . . . . . . . . . . 11
5. UPnP Support . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Comparison to RFC 7084 . . . . . . . . . . . . . . . . . . . 12
7. Code Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Usage Scenarios . . . . . . . . . . . . . . . . . . 17
Appendix B. End-User Network Architecture . . . . . . . . . . . 18
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
This document defines IPv4 service continuity features over an
IPv6-only network for residential or small office routers (referred
to as "IPv6 Transition CE Routers") in order to establish an industry
baseline for transition features to be implemented on such routers.
These routers rely upon requirements for IPv6 CE routers defined in
[RFC7084]. The scope of this document is to ensure IPv4 service
continuity support for devices in the LAN side. This ensures that
remote IPv4-only services continue to be accessible, for both
IPv4-only and IPv6-only applications and devices, located in the LAN
side behind an IPv6 Transition CE Router connected to an IPv6-only
access network. These ISP access networks are typically referred to
as Wide Area Networks (WANs), even if they may be metropolitan or
regional in some cases. Figure 1 presents a simplified view of this
architecture.
+------------+ +------------+ \
| IPv4-only | | IPv4/IPv6 | \
| Remote | | Remote | |
| Host | | Host | | Internet
+--------+---+ +---+--------+ |
| | /
| | /
+-+-----------+-+ \
| Service | \
| Provider | \
| Router | | Service
+-------+-------+ | Provider
| IPv6-only | Network
| Customer /
| Internet Connection /
| /
+------+--------+ \
| IPv6 | \
| Transition CE | \
| Router | |
+---+-------+---+ |
LAN A | | LAN B | End-User
-+----------------+- -+-----+-------------+- | Network(s)
| | | |
+---+------+ +----+-----+ +-----+----+ |
| IPv6-only| | IPv4-only| |IPv4/IPv6 | /
| Host | | Host | | Host | /
+----------+ +----------+ +----------+ /
Figure 1: Simplified Typical IPv6-Only Access Network
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This document covers a set of IP transition techniques required when
ISPs have, or want to have, an IPv6-only access network. This is a
common situation when sufficient IPv4 addresses are no longer
available for every possible customer and device, which causes IPv4
addresses to become prohibitively expensive. This, in turn, may
result in service providers provisioning IPv6-only WAN access. At
the same time, they need to ensure that both IPv4-only and IPv6-only
devices and applications in the customer networks can still reach
IPv4-only devices and applications on the Internet.
This document specifies the IPv4 service continuity mechanisms to be
supported by an IPv6 Transition CE Router and relevant provisioning
or configuration information differences from [RFC7084].
This document is not a recommendation for service providers to use
any specific transition mechanism.
Automatic provisioning of more complex topology than a single router
with multiple LAN interfaces may be handled by means of the Home
Networking Control Protocol (HNCP) [RFC7788], which is out of the
scope of this document.
Since it is impossible to know prior to sale which transition
mechanism a device will need over its lifetime, an IPv6 Transition CE
Router intended for the retail market MUST support all the IPv4aaS
transition mechanisms listed in this document. Service providers
that specify feature sets for the IPv6 Transition CE Router may
define a different set of features from those included in this
document, for example, features that support only some of the
transition mechanisms enumerated in this document.
Appendices A and B contain a complete description of the usage
scenarios and end-user network architecture, respectively. These
appendices, along with [RFC7084], will facilitate a clearer
understanding of this document.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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2. Terminology
This document uses the same terms as in [RFC7084], with minor
clarifications.
"IPv4aaS" stands for "IPv4-as-a-Service", meaning transition
technologies for delivering IPv4 in IPv6-only connectivity.
The term "IPv6 transition Customer Edge Router with IPv4aaS"
(shortened as "IPv6 Transition CE Router") is defined as an IPv6
Customer Edge Router that provides features for the delivery of IPv4
services over an IPv6-only WAN network, including IPv6-IPv4
communications.
The term "WAN Interface" as used in this document is defined as an
IPv6 Transition CE Router attachment to an IPv6-only link used to
provide connectivity to a service provider network, including link
Internet-layer (or higher layers) tunnels, such as IPv4-in-IPv6
tunnels.
3. Requirements
The IPv6 Transition CE Router MUST comply with [RFC7084] ("Basic
Requirements for IPv6 Customer Edge Routers"). This document adds
new requirements, as described in the following subsections.
3.1. LAN-Side Configuration
A new LAN requirement is added, which is, in fact, common in regular
IPv6 Transition CE Routers, and is required by most of the transition
mechanisms:
L-1: The IPv6 Transition CE Router MUST implement a DNS proxy as
described in [RFC5625] ("DNS Proxy Implementation Guidelines").
3.2. Transition Technologies Support for IPv4 Service Continuity (IPv4-
as-a-Service)
The main target of this document is the support of IPv6-only WAN
access. To enable legacy IPv4 functionality, this document also
includes the support of IPv4-only devices and applications in the
customer LANs, as well as IPv4-only services on the Internet. Thus,
both IPv4-only and IPv6-only devices in the customer-side LANs of the
IPv6 Transition CE Router are able to reach the IPv4-only services.
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Note that this document only configures IPv4aaS in the IPv6
Transition CE Router itself; it does not forward such information to
devices attached to the LANs. Thus, the WAN configuration and
availability of native IPv4 or IPv4aaS are transparent for the
devices attached to the LANs.
This document takes no position on simultaneous operation of one or
several transition mechanisms and/or native IPv4.
In order to seamlessly provide IPv4 service continuity in the
customer LANs and allow automated IPv6 transition mechanism
provisioning, the following general transition requirements are
defined.
General transition requirements:
TRANS-1: The IPv6 Transition CE Router MUST support the DHCPv6 S46
priority options described in [RFC8026] ("Unified IPv4-in-
IPv6 Softwire Customer Premises Equipment (CPE): A
DHCPv6-Based Prioritization Mechanism").
TRANS-2: The IPv6 Transition CE Router MUST have a GUI and either a
CLI or API (or both) to manually enable/disable each of the
supported transition mechanisms.
TRANS-3: If an IPv6 Transition CE Router supports more than one LAN
subnet, the IPv6 Transition CE Router MUST allow
appropriate subnetting and configuration of the address
space among several interfaces. In some transition
mechanisms, this may require differentiating mappings/
translations on a per-interface basis.
In order to allow the service provider to disable all the transition
mechanisms and/or choose the most convenient one, the IPv6 Transition
CE Router MUST follow the following configuration steps:
CONFIG-1: Request the relevant configuration options for each
supported transition mechanisms, which MUST remain
disabled at this step.
CONFIG-2: Following the steps in Section 1.4 of [RFC8026], MUST
check for a valid match in OPTION_S46_PRIORITY, which
allows enabling/disabling a transition mechanism.
CONFIG-3: Keep disabled all the transition mechanisms if no match is
found between the priority list and the candidate list,
unless a NAT64 [RFC6146] prefix has been configured, in
which case, 464XLAT [RFC6877] MUST be enabled.
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Because 464XLAT has no DHCPv6 configuration options, it can't
currently be included in the OPTION_S46_PRIORITY. In the future, an
update of [RFC8026] or a NAT64 DHCPv6 configuration option may enable
it. Meanwhile, if an operator provides 464XLAT, it needs to ensure
that OPTION_S46_PRIORITY is not sent for any other transition
mechanism to the relevant customers.
The following subsections describe the requirements for supporting
each one of the transition mechanisms. An IPv6 Transition CE Router
intended for the retail market MUST support all of them.
3.2.1. 464XLAT
464XLAT [RFC6877] is a technique to provide IPv4 service over an
IPv6-only access network without encapsulation. This architecture
assumes a Stateful NAT64 [RFC6146] function deployed at the service
provider or a third-party network.
The IPv6 Transition CE Router MUST support customer-side translator
(CLAT) functionality [RFC6877] if intended for the retail market. If
464XLAT is supported, it MUST be implemented according to [RFC6877].
The following IPv6 Transition CE Router requirements also apply.
464XLAT requirements:
464XLAT-1: Unless a dedicated /64 prefix has been acquired, either
by using DHCPv6-PD (Dynamic Host Configuration Protocol
for IPv6 Prefix Delegation) or by alternative means, the
IPv6 Transition CE Router MUST perform IPv4 Network
Address Translation (NAT) on IPv4 traffic translated
using the CLAT.
464XLAT-2: The IPv6 Transition CE Router SHOULD support IGD-PCP IWF
[RFC6970] ("Universal Plug and Play (UPnP) Internet
Gateway Device - Port Control Protocol Interworking
Function (IGD-PCP IWF)").
464XLAT-3: If the Port Control Protocol (PCP) [RFC6887] is
implemented, the IPv6 Transition CE Router MUST also
implement [RFC7291] ("DHCP Options for the Port Control
Protocol (PCP)"). Following [RFC6887], if no PCP server
is configured, the IPv6 Transition CE Router MAY verify
if the default gateway or the NAT64 is the PCP server.
The IPv6 Transition CE Router MUST use plain IPv6 mode
(i.e., not IPv4-in-IPv6 encapsulation) to send PCP
requests to the server.
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464XLAT-4: The IPv6 Transition CE Router MUST implement [RFC7050]
("Discovery of the IPv6 Prefix Used for IPv6 Address
Synthesis") in order to discover the provider-side
translator (PLAT) translation IPv4 and IPv6
prefix(es)/suffix(es).
464XLAT-5: If PCP is implemented, the IPv6 Transition CE Router MUST
follow [RFC7225] ("Discovering NAT64 IPv6 Prefixes Using
the Port Control Protocol (PCP)") in order to learn the
PLAT-side translation IPv4 and IPv6 prefix(es)/suffix(es)
used by an upstream PCP-controlled NAT64 device.
464XLAT-6: If the network provides several choices for the
discovery/learning of the NAT64 prefix, the priority to
use one or the other MUST follow this order: 1) [RFC7225]
and 2) [RFC7050].
The NAT64 prefix could be discovered by means of the method defined
in [RFC7050] only if the service provider uses DNS64 [RFC6147]. It
may be the case that the service provider does not use or does not
trust DNS64 [RFC6147] because the DNS configuration at the CE (or
hosts behind the CE) can be modified by the customer. In that case,
the service provider may opt to configure the NAT64 prefix by means
of the option defined in [RFC7225]. This can also be used if the
service provider uses DNS64 [RFC6147].
3.2.2. Dual-Stack Lite (DS-Lite)
DS-Lite [RFC6333] enables continued support for IPv4 services.
DS-Lite enables a broadband service provider to share IPv4 addresses
among customers by combining two well-known technologies: IP in IP
(IPv4-in-IPv6) and Network Address Translation (NAT). It is expected
that DS-Lite traffic is forwarded over the IPv6 Transition CE
Router's native IPv6 WAN interface and not encapsulated in another
tunnel.
The IPv6 Transition CE Router MUST implement DS-Lite B4 functionality
[RFC6333] if intended for the retail market. If DS-Lite is
supported, it MUST be implemented according to [RFC6333]. The
following IPv6 Transition CE Router requirements also apply.
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DS-Lite requirements:
DSLITE-1: The IPv6 Transition CE Router MUST support configuration
of DS-Lite via the DS-Lite DHCPv6 option [RFC6334]
("Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
Option for Dual-Stack Lite"). The IPv6 Transition CE
Router MAY use other mechanisms to configure DS-Lite
parameters. Such mechanisms are outside the scope of this
document.
DSLITE-2: The IPv6 Transition CE Router SHOULD support IGD-PCP IWF
[RFC6970].
DSLITE-3: If PCP [RFC6887] is implemented, the IPv6 Transition CE
Router SHOULD implement [RFC7291]. If PCP [RFC6887] is
implemented and a PCP server is not configured, the IPv6
Transition CE Router MUST assume, by default, that the
Address Family Transition Router (AFTR, commonly called
"CGN" - Carrier-Grade NAT) is the PCP server. The IPv6
Transition CE Router MUST use plain IPv6 mode (i.e., not
IPv4-in-IPv6 encapsulation) to send PCP requests to the
server. The term "default" above is to be interpreted as
pertaining to a configuration as applied by a vendor prior
to the administrator changing it for its initial
activation.
DSLITE-4: The IPv6 Transition CE Router MUST NOT perform IPv4
Network Address Translation (NAT) on IPv4 traffic
encapsulated using DS-Lite [RFC6333].
3.2.3. Lightweight 4over6 (lw4o6)
lw4o6 [RFC7596] specifies an extension to DS-Lite that moves the NAPT
function from the DS-Lite tunnel concentrator to the tunnel client
located in the IPv6 Transition CE Router, removing the requirement
for an AFTR (CGN) function in the tunnel concentrator and reducing
the amount of centralized state.
The IPv6 Transition CE Router MUST implement lwB4 functionality
[RFC7596] if intended for the retail market. If DS-Lite is
implemented, lw4o6 SHOULD be implemented as well. If lw4o6 is
supported, it MUST be implemented according to [RFC7596]. The
following IPv6 Transition CE Router requirements also apply.
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lw4o6 requirements:
LW4O6-1: The IPv6 Transition CE Router MUST support configuration of
lw4o6 via the lw4o6 DHCPv6 options [RFC7598] ("DHCPv6
Options for Configuration of Softwire Address and Port-
Mapped Clients"). The IPv6 Transition CE Router MAY use
other mechanisms to configure lw4o6 parameters. Such
mechanisms are outside the scope of this document.
LW4O6-2: The IPv6 Transition CE Router MUST support the DHCPv4-over-
DHCPv6 (DHCP 4o6) transport described in [RFC7341]
("DHCPv4-over-DHCPv6 (DHCP 4o6) Transport").
LW4O6-3: The IPv6 Transition CE Router MAY support Dynamic
Allocation of Shared IPv4 Addresses as described in
[RFC7618] ("Dynamic Allocation of Shared IPv4 Addresses").
3.2.4. MAP-E
Mapping of Address and Port with Encapsulation (MAP-E) [RFC7597] is a
mechanism for transporting IPv4 packets across an IPv6 network using
IP encapsulation. MAP-E includes an algorithmic mechanism for
mapping between IPv6 and IPv4 addresses.
The IPv6 Transition CE Router MUST support MAP-E CE functionality
[RFC7597] if intended for the retail market. If MAP-E is supported,
it MUST be implemented according to [RFC7597]. The following IPv6
Transition CE Router requirements also apply.
MAP-E requirements:
MAPE-1: The IPv6 Transition CE Router MUST support configuration of
MAP-E via the MAP-E DHCPv6 options [RFC7598]. The IPv6
Transition CE Router MAY use other mechanisms to configure
MAP-E parameters. Such mechanisms are outside the scope of
this document.
MAPE-2: The IPv6 Transition CE Router MAY support Dynamic Allocation
of Shared IPv4 Addresses as described in [RFC7618].
3.2.5. MAP-T
MAP-T [RFC7599] is a mechanism similar to MAP-E, differing from it in
that MAP-T uses IPv4-IPv6 translation, instead of encapsulation, as
the form of IPv6 domain transport.
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The IPv6 Transition CE Router MUST support MAP-T CE functionality
[RFC7599] if intended for the retail market. If MAP-T is supported,
it MUST be implemented according to [RFC7599]. The following IPv6
Transition CE Router requirements also apply.
MAP-T requirements:
MAPT-1: The IPv6 Transition CE Router MUST support configuration of
MAP-T via the MAP-T DHCPv6 options [RFC7598]. The IPv6
Transition CE Router MAY use other mechanisms to configure
MAP-T parameters. Such mechanisms are outside the scope of
this document.
MAPT-2: The IPv6 Transition CE Router MAY support Dynamic Allocation
of Shared IPv4 Addresses as described in [RFC7618].
4. IPv4 Multicast Support
Existing IPv4 deployments support IPv4 multicast for services such as
IPTV. In the transition phase, it is expected that multicast
services will still be provided using IPv4 to the customer LANs.
If the IPv6 Transition CE Router supports delivery of IPv4 multicast
services, then it MUST support [RFC8114] ("Delivery of IPv4 Multicast
Services to IPv4 Clients over an IPv6 Multicast Network") and
[RFC8115] ("DHCPv6 Option for IPv4-Embedded Multicast and Unicast
IPv6 Prefixes").
5. UPnP Support
If the UPnP WANIPConnection:2 service [UPnP-WANIPC][OCF-IGD] is
enabled on a CE router, but cannot be associated with an IPv4
interface established by an IPv4aaS mechanism or cannot determine
which ports are available, an AddPortMapping() or AddAnyPortMapping()
action MUST be rejected with error code 729
("ConflictWithOtherMechanisms"). Port availability could be
determined through PCP or access to a configured port set (if the
IPv4aaS mechanism limits the available ports).
An AddPortMapping() request for a port that is not available MUST
result in "ConflictInMappingEntry".
An AddAnyPortMapping() request for a port that is not available
SHOULD result in a successful mapping with an alternative
"NewReservedPort" value from within the configured port set range or
as assigned by PCP as per Section 5.6.1 of [RFC6970].
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Note that IGD:1 and its WANIPConnection:1 service have been
deprecated by OCF (Open Connectivity Foundation) [OCF-IGD].
6. Comparison to RFC 7084
This document doesn't include support for 6rd [RFC5969] because it is
an IPv6-in-IPv4 tunneling.
Regarding DS-LITE [RFC6333], this document includes slightly
different requirements related to the support of PCP [RFC6887],
IGD-PCP IWF [RFC6970], and the prioritization of the transition
mechanisms, including dual-stack.
7. Code Considerations
At the time of this writing, one of the apparent main issues for
vendors with regard to including new functionalities, such as support
for new transition mechanisms, is the lack of space in the flash (or
equivalent) memory. However, it has been confirmed from existing
open-source implementations (e.g., OpenWRT/LEDE, Linux, and VPP) that
adding the support for the new transition mechanisms requires around
10-12 KBs because most of the code base is shared among several
transition mechanisms, which are already supported by [RFC7084]. A
single data plane is common to all of them, which typically means, in
popular CEs already in the market [OpenWRT], the new required code is
only about 0.15% of the total existing code size.
In general, the new requirements don't have extra cost in terms of
RAM memory, nor other hardware requirements such as more powerful
CPUs, if compared to the cost of NAT44 code. Thus, existing hardware
should be able to support all of them with minimal impact.
The other issue seems to be the cost of developing the code for those
new functionalities. However, at the time of writing this document,
it has been confirmed that there are several open-source versions of
the required code for supporting all the new transition mechanisms,
and several vendors already have implementations and provided them to
ISPs. Therefore, the development cost is negligible, and only
integration and testing cost may become an issue.
Finally, in some cases, operators supporting several transition
mechanisms may need to consider training costs for staff in all the
techniques for the operation and management of these mechanisms, even
if the costs are not directly caused by supporting this document but
because of business decisions.
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8. Security Considerations
The IPv6 Transition CE Router must comply with the Security
Considerations in [RFC7084] as well as those for each transition
mechanism implemented by the IPv6 Transition CE Router.
As described in the Security Considerations of [RFC8026] and
[RFC8415], there are generic DHCP security issues, which, in the case
of this document, mean that malicious nodes may alter the priority of
the transition mechanisms.
Access network architecture for securing DHCP within the access
network is out of scope for this document. Securing DHCP in the LAN
is also not in scope. DHCP packets MUST NOT be forwarded between LAN
and WAN interfaces of an IPv6 Transition CE Router.
9. IANA Considerations
This document has no IANA actions.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
<https://www.rfc-editor.org/info/rfc5625>.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, DOI 10.17487/RFC5969, August 2010,
<https://www.rfc-editor.org/info/rfc5969>.
[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>.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
DOI 10.17487/RFC6147, April 2011,
<https://www.rfc-editor.org/info/rfc6147>.
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[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<https://www.rfc-editor.org/info/rfc6333>.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, DOI 10.17487/RFC6334, August 2011,
<https://www.rfc-editor.org/info/rfc6334>.
[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>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and
Play (UPnP) Internet Gateway Device - Port Control
Protocol Interworking Function (IGD-PCP IWF)", RFC 6970,
DOI 10.17487/RFC6970, July 2013,
<https://www.rfc-editor.org/info/rfc6970>.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis",
RFC 7050, DOI 10.17487/RFC7050, November 2013,
<https://www.rfc-editor.org/info/rfc7050>.
[RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
Requirements for IPv6 Customer Edge Routers", RFC 7084,
DOI 10.17487/RFC7084, November 2013,
<https://www.rfc-editor.org/info/rfc7084>.
[RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
Port Control Protocol (PCP)", RFC 7225,
DOI 10.17487/RFC7225, May 2014,
<https://www.rfc-editor.org/info/rfc7225>.
[RFC7291] Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
the Port Control Protocol (PCP)", RFC 7291,
DOI 10.17487/RFC7291, July 2014,
<https://www.rfc-editor.org/info/rfc7291>.
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[RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport",
RFC 7341, DOI 10.17487/RFC7341, August 2014,
<https://www.rfc-editor.org/info/rfc7341>.
[RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the Dual-
Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
July 2015, <https://www.rfc-editor.org/info/rfc7596>.
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015,
<https://www.rfc-editor.org/info/rfc7597>.
[RFC7598] Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
Configuration of Softwire Address and Port-Mapped
Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
<https://www.rfc-editor.org/info/rfc7598>.
[RFC7599] Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
and T. Murakami, "Mapping of Address and Port using
Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July
2015, <https://www.rfc-editor.org/info/rfc7599>.
[RFC7618] Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M.
Boucadair, "Dynamic Allocation of Shared IPv4 Addresses",
RFC 7618, DOI 10.17487/RFC7618, August 2015,
<https://www.rfc-editor.org/info/rfc7618>.
[RFC8026] Boucadair, M. and I. Farrer, "Unified IPv4-in-IPv6
Softwire Customer Premises Equipment (CPE): A DHCPv6-Based
Prioritization Mechanism", RFC 8026, DOI 10.17487/RFC8026,
November 2016, <https://www.rfc-editor.org/info/rfc8026>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>.
[RFC8115] Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6
Option for IPv4-Embedded Multicast and Unicast IPv6
Prefixes", RFC 8115, DOI 10.17487/RFC8115, March 2017,
<https://www.rfc-editor.org/info/rfc8115>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
10.2. Informative References
[IPv6Survey]
Palet Martinez, J., "Best Current Operational Practice for
operators: IPv6 Prefix Assignment for end-customers --
persistent vs non-persistent and what size to choose",
January 2018,
<https://indico.uknof.org.uk/event/41/contribution/5/
material/slides/0.pdf>.
[OCF-IGD] Open Connectivity Foundation, "Internet Gateway Device
(IGD) V 2.0", March 2015,
<https://openconnectivity.org/developer/specifications/
upnp-resources/upnp/internet-gateway-device-igd-v-2-0>.
[OpenWRT] OpenWRT, "Packages", <https://openwrt.org/packages/start>.
[RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
2016, <https://www.rfc-editor.org/info/rfc7788>.
[UPnP-IGD]
UPnP Forum, "InternetGatewayDevice:2 Device Template
Version 1.01", December 2010, <http://upnp.org/specs/gw/
UPnP-gw-InternetGatewayDevice-v2-Device.pdf>.
[UPnP-WANIPC]
UPnP Forum, "WANIPConnection:2 Service", September 2010,
<http://upnp.org/specs/gw/
UPnP-gw-WANIPConnection-v2-Service.pdf>.
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Appendix A. Usage Scenarios
The situation of ongoing IPv6 deployment and a lack of IPv4 addresses
is not happening at the same pace in every country and even within
every country for every ISP. For different technical, financial,
commercial/marketing, and socio-economic reasons, each network is
transitioning at their own pace; the global transition timings cannot
be reliably estimated.
Different studies (for example, [IPv6Survey]) also show that IPv6
deployment is a changing situation. In a single country, not all
operators will necessarily provide IPv6 support. Consumers may also
switch ISPs and use the same IPv6 Transition CE Router with either an
ISP that provides IPv4-only or an ISP that provides IPv6 with
IPv4aaS.
So, to cover all those evolving situations, an IPv6 Transition CE
Router is required, at least from the perspective of transition
support.
Moreover, because some services and service providers will remain
IPv4-only for an undetermined period of time, IPv4 service continuity
is required. Thus, there is a need for CEs to support IPv4aaS
indefinitely.
Based on these premises, this document ensures that the IPv6
Transition CE Router allows the continued transition from networks
that today may provide access with dual-stack or IPv6-in-IPv4 (as
described in [RFC7084]) to networks that provide IPv6-only access
with IPv4aaS.
Considering that situation and different possible usage cases, the
IPv6 Transition CE Router described in this document is expected to
be used in residential/household; small office, home office (SOHO);
and small/medium enterprise (SME). Common usage is any kind of
Internet access (web, email, streaming, online gaming, etc.), and
more advanced requirements include inbound connections (IP cameras,
web, DNS, email, VPN, etc.).
The above is not intended to be a comprehensive list of all the
possible usage cases, just an overview. In fact, combinations of the
above usages are also possible, along with situations where the same
CE is used at different times in different scenarios or even with
different IPv4aaSes at different service providers.
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The mechanisms for allowing inbound connections are naturally
available in any IPv6 router when using IPv6 Global Unicast Addresses
(GUAs), unless they are blocked by firewall rules, which may require
some manual configuration.
However, in the case of IPv4aaS, because of the usage of private IPv4
addresses and NAT and depending on the specific transition mechanism,
inbound connections typically require some degree of more complex
manual configuration, such as setting up a DMZ, setting up virtual
servers, or setting up port/protocol forwarding. In general, IPv4 CE
Routers already provide a GUI, CLI, or API to manually configure
them, or provide the possibility to set up the CE in bridge mode, so
another Router behind the original CE, takes care of inbound
connections. The requirements for that support are out of the scope
of this document.
Who provides the IPv6 Transition CE Router is not relevant. In most
cases, the service provider is responsible for provisioning/managing,
at least on the WAN side. Commonly, the user has access to configure
the LAN interfaces, firewall, DMZ, and many other features. However,
in many cases, the user must supply or may replace the IPv6
Transition CE Router. This underscores the importance of the IPv6
Transition CE Routers fulfilling the requirements defined in this
document.
The IPv6 Transition CE Router described in this document is not
intended for usage in other scenarios, such as large enterprises,
data centers, content providers, etc. Even if the documented
requirements meet their needs, they may have additional requirements,
which are out of the scope of this document.
Appendix B. End-User Network Architecture
An end-user network will likely support both IPv4 and IPv6 (see
Section 1 and Appendix A). It is not expected that end users will
change their existing network topology with the introduction of IPv6.
There are some differences in how IPv6 works and is provisioned;
these differences have implications for the network architecture.
A typical IPv4 end-user network consists of a "plug and play" router
with NAT functionality and a single link upstream, connected to the
service provider network.
From the perspective of an IPv4 user behind an IPv6 Transition CE
Router, this doesn't change.
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However, while a typical IPv4 NAT deployment, by default, blocks all
incoming connections and may allow opening of ports using a Universal
Plug and Play Internet Gateway Device (UPnP IGD) [UPnP-IGD][OCF-IGD]
or some other firewall control protocol, in the case of an IPv6-only
access and IPv4aaS, that may not be feasible depending on specific
transition mechanism details. PCP [RFC6887] may be an alternative
solution.
Another consequence of using IPv4 private address space in the end-
user network is that it provides stable addressing; that is, it
doesn't change, even when you change service providers, and the
addresses are always usable even when the WAN interface is down or
the customer edge router has not yet been provisioned. In the case
of IPv6-only access, private IPv4 addresses are also available if the
IPv4aaS transition mechanism keeps running the NAT interface towards
the LAN side when the WAN interface is down.
More advanced routers support dynamic routing (which learns routes
from other routers), and advanced end users can build arbitrary,
complex networks using manual configuration of address prefixes
combined with a dynamic routing protocol. Once again, this is true
for both IPv4 and IPv6.
In general, the end-user network architecture for IPv6 should provide
equivalent or better capabilities and functionality than the current
IPv4 architecture.
The end-user network is a stub network in the sense that is not
providing transit to other external networks. However, HNCP
[RFC7788] allows support for automatic provisioning of downstream
routers. Figure 2 illustrates the model topology for the end-user
network.
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+---------------+ \
| Service | \
| Provider | \
| Router | | Service
+-------+-------+ | Provider
| IPv6-only | Network
| Customer /
| Internet Connection /
| /
+------+--------+ \
| IPv6 | \
| Transition CE | \
| Router | |
+---+-------+---+ |
Network A | | Network B |
-+----------------+-+- -+---+-------------+- |
| | | | |
+---+------+ | +----+-----+ +-----+----+ |
| IPv6 | | | IPv4 | |IPv4/IPv6 | |
| Host | | | Host | | Host | |
+----------+ | +----------+ +----------+ | End-User
| | Network(s)
+------+--------+ |
| IPv6 | |
| Router | |
+------+--------+ |
Network C | |
-+-------------+--+- |
| | |
+---+------+ +----+-----+ |
| IPv6 | | IPv6 | /
| Host | | Host | /
+----------+ +----------+ /
Figure 2: Example of a Typical End-User Network
This architecture describes the:
o Basic capabilities of the IPv6 Transition CE Router
o Provisioning of the WAN interface connecting to the service
provider
o Provisioning of the LAN interfaces
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The IPv6 Transition CE Router may be manually configured in an
arbitrary topology with a dynamic routing protocol or HNCP [RFC7788].
Automatic provisioning and configuration are described for a single
IPv6 Transition CE Router only.
Acknowledgements
Thanks to Mikael Abrahamsson, Fred Baker, Mohamed Boucadair, Brian
Carpenter, Lorenzo Colitti, Alejandro D'Egidio, Ian Farrer, Lee
Howard, Richard Patterson, Barbara Stark, Ole Troan, and James
Woodyatt for their review and comments in this and/or previous draft
versions of this document. Thanks also for the Last Call reviews by
Dan Romascanu (OPS-DIR); Christian Huitema (SEC-DIR); Daniele
Ceccarelli (RTG-DIR); Martin Stiemerling (TSV-ART); Matthew Miller
(Gen-ART); and Alissa Cooper, Benjamin Kaduk, Suresh Krishnan, Ben
Campbell, Spencer Dawkins, Mirja Kuhlewind, and Adam Roach (all
IESG).
Authors' Addresses
Jordi Palet Martinez
The IPv6 Company
Molino de la Navata, 75
La Navata - Galapagar, Madrid 28420
Spain
Email: jordi.palet@theipv6company.com
URI: http://www.theipv6company.com/
Hans M.-H. Liu
D-Link Systems, Inc.
17595 Mount Herrmann St.
Fountain Valley, California 92708
United States of America
Email: hans.liu@dlinkcorp.com
URI: https://www.dlink.com/
Masanobu Kawashima
NEC Platforms, Ltd.
2-3, Kanda-Tsukasamachi
Chiyoda-ku, Tokyo 101-8532
Japan
Email: kawashimam@vx.jp.nec.com
URI: https://www.necplatforms.co.jp/en/
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