An IPv6 transition mechanism is a technology that facilitates the transitioning of the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

from the

Internet Protocol version 4 Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version de ...

(IPv4) infrastructure in use since 1983 to the successor addressing and routing system of

Internet Protocol Version 6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv ...

(IPv6). As IPv4 and IPv6 networks are not directly interoperable, transition technologies are designed to permit hosts on either network type to communicate with any other host. To meet its technical criteria, IPv6 must have a straightforward transition plan from the current IPv4. The

Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

(IETF) conducts working groups and discussions through the IETF

Internet Draft An Internet Draft (I-D) is a document published by the Internet Engineering Task Force (IETF) containing preliminary technical specifications, results of networking-related research, or other technical information. Often, Internet Drafts are int ...

s and

Request for Comments A Request for Comments (RFC) is a publication in a series from the principal technical development and standards-setting bodies for the Internet, most prominently the Internet Engineering Task Force (IETF). An RFC is authored by individuals or g ...

processes to develop these transition technologies towards that goal. Some basic IPv6 transition mechanisms are defined in RFC 4213.

Stateless IP/ICMP Translation

Stateless IP/ ICMP Translation (SIIT) translates between the packet header formats in

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv ...

and IPv4. The SIIT method defines a class of IPv6 addresses called ''IPv4-translated'' addresses. They have the prefix and may be written as , in which the IPv4 formatted address refers to an ''IPv6-enabled'' node. The prefix was chosen to yield a zero-valued

checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data ...

to avoid changes to the transport protocol header checksum. The algorithm can be used in a solution that allows IPv6 hosts that do not have a permanently assigned IPv4 address to communicate with IPv4-only hosts. Address assignment and routing details are not addressed by the specification. SIIT can be viewed as a special case of stateless network address translation. The specification is a product of the NGTRANS IETF working group, and was initially drafted in February 2000 by E. Nordmark of Sun Microsystems. It was revised in 2011, and in 2016 its current revision was published.

Tunnel broker

A tunnel broker provides IPv6 connectivity by encapsulating IPv6 traffic in IPv4 Internet transit links, typically using

6in4 6in4 is an IPv6 transition mechanism for migrating from Internet Protocol version 4 (IPv4) to IPv6. It is a tunneling protocol that encapsulates IPv6 packets on specially configured IPv4 links according to the specifications of . The IP protocol ...

. This establishes IPv6 tunnels within the IPv4 Internet. The tunnels may be managed with the Tunnel Setup Protocol (TSP) or AYIYA.

6rd

6rd is a mechanism to facilitate rapid deployment of the IPv6 service across IPv4 infrastructures of Internet service providers (

ISP An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise private ...

s). It uses stateless address mappings between IPv4 and

addresses, and transmits

packets across automatic tunnels that follow the same optimized routes between customer nodes as IPv4 packets. It was used for an early large deployment of an IPv6 service with native addresses during 2007 (RFC 5569). The standard-track specification of the protocol is in RFC 5969.

Transport Relay Translation

RFC 3142 defines the Transport Relay Translation (TRT) method. TRT employs DNS translation between AAAA and A records known as '' DNS-ALG'' as defined in RFC 2694.

NAT64

NAT64 NAT64 is an IPv6 transition mechanism that facilitates communication between IPv6 and IPv4 hosts by using a form of network address translation (NAT). The NAT64 gateway is a translator between IPv4 and IPv6 protocols, for which function it need ...

is a mechanism to allow IPv6 hosts to communicate with IPv4 servers. The NAT64 server is the endpoint for at least one IPv4 address and an IPv6 network segment of 32-bits, e.g., . The IPv6 client embeds the IPv4 address with which it wishes to communicate using these bits, and sends its packets to the resulting address. The NAT64 server then creates a NAT-mapping between the IPv6 and the IPv4 address, allowing them to communicate.

DNS64

DNS64 describes a DNS server that when asked for a domain's

AAAA record This list of DNS record types is an overview of resource records (RRs) permissible in zone files of the Domain Name System The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resour ...

s, but only finds

A record This list of DNS record types is an overview of resource records (RRs) permissible in zone files of the Domain Name System The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other reso ...

s, synthesizes the AAAA records from the A records. The first part of the synthesized IPv6 address points to an IPv6/IPv4 translator and the second part embeds the IPv4 address from the A record. The translator in question is usually a NAT64 server. The standard-track specification of DNS64 is in RFC 6147. There are two noticeable issues with this transition mechanism: * It only works for cases where DNS is used to find the remote host address, if IPv4 literals are used the DNS64 server will never be involved. * Because the DNS64 server needs to return records not specified by the domain owner,

DNSSEC The Domain Name System Security Extensions (DNSSEC) are a suite of extension specifications by the Internet Engineering Task Force (IETF) for securing data exchanged in the Domain Name System (DNS) in Internet Protocol (IP) networks. The protoc ...

validation against the

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the su ...

will fail in cases where the DNS server doing the translation is not the domain owner's server. # DNS resolver 2606:4700:4700:64 synthesizes AAAA records for # ipv6test.google.com to a NAT64 address: 64::ff9b:: nslookup ipv6test.google.com 2606:4700:4700::64 Non-authoritative answer: ipv6test.google.com canonical name = ipv6test.l.google.com. Name: ipv6test.l.google.com Address: 64:ff9b::8efa:c3e4

ISATAP

ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) is an IPv6 transition mechanism meant to transmit IPv6 packets between dual-stack nodes on top of an IPv4 network. Unlike 6over4 (an older similar protocol using IPv4 multicast), ISATAP uses IPv4 as a virtual nonbroadcast multiple-access network (NBMA) data link layer, so that it does not require the underlying IPv4 network infrastructure to support multicast.

464XLAT

464XLAT (RFC 6877) allows clients on IPv6-only networks to access IPv4-only Internet services, such as Skype. The client uses a SIIT translator to convert packets from IPv4 to IPv6. These are then sent to a

translator which translates them from IPv6 back into IPv4 and on to an IPv4-only server. The client translator may be implemented on the client itself or on an intermediate device and is known as the CLAT (Customer-side transLATor). The NAT64 translator, or PLAT (Provider-side transLATor), must be able to reach both the server and the client (through the CLAT). The use of NAT64 limits connections to a client-server model using UDP, TCP, and ICMP. ;Implementations * There is a CLAT implementation for Android
Android CLAT

T-Mobile USA T-Mobile US, Inc. is an American wireless network operator headquartered in Overland Park, Kansas Overland Park ( ) is the second-most populous city in the U.S. state of Kansas. Located in Johnson County, Kansas, it is one of four principal ...

provides NAT64 with T-Mobile's IPv6-only service. *

Orange Poland Orange Polska (formerly Telekomunikacja Polska) is a Polish telecommunications provider established in December 1991. It is a public company traded on the Warsaw Stock Exchange, with a controlling stake owned by Orange S.A., the latter controlli ...

began IPv6-only (CLAT/NAT64/DNS) service in September 2013. * Android has a native CLAT implementation since Jelly Bean 4.3, released in 2013. *

Windows Phone Windows Phone (WP) is a discontinued family of mobile operating systems developed by Microsoft for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone featured a new user interface derived from the Metro design l ...

introduced a native CLAT implementation in 2014 with WP 8.1. *

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...

has a native 464XLAT implementation for desktop and mobile, since the Creators Update in 2017. It is enabled for WWAN interfaces when the Mobile Operator has enabled 464XLAT on the network. *

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

starts to have native CLAT support in Ventura, released in 2022. *

iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also include ...

has a native CLAT implementation since version 12.0, released in 2018. Additionally, Apple requires all apps submitted to the

App Store An App Store (or app marketplace) is a type of digital distribution platform for computer software called applications, often in a mobile context. Apps provide a specific set of functions which, by definition, do not include the running of the c ...

to work on IPv6 networks.
clatd
is a CLAT implementation for

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...

. * FreeBSD has had CLAT implementations since 11.3 and 12.1.

Dual-Stack Lite (DS-Lite)

Dual-Stack Lite technology does not involve allocating an IPv4 address to

customer-premises equipment In telecommunications, a customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment located at a subscriber's premises and connected with a carrier's telecommunication circuit at the demarcation po ...

(CPE) for providing Internet access. The CPE distributes private IPv4 addresses for the LAN clients, according to the networking requirement in the local area network. The CPE encapsulates IPv4 packets within IPv6 packets. The CPE uses its global IPv6 connection to deliver the packet to the ISP's

carrier-grade NAT Carrier-grade NAT (CGN or CGNAT), also known as large-scale NAT (LSN), is a type of Network address translation (NAT) for use in IPv4 network design. With CGNAT, end sites, in particular residential networks, are configured with private network a ...

(CGN), which has a global IPv4 address. The original IPv4 packet is recovered and NAT is performed upon the IPv4 packet and is routed to the public IPv4 Internet. The CGN uniquely identifies traffic flows by recording the CPE public IPv6 address, the private IPv4 address, and TCP or UDP port number as a session. Lightweight

4over6 4over6 is an IPv6 transition technology. It is intended as a mechanism for Internet service providers to provide continued access to the IPv4 Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one o ...

extends DS-Lite by moving the NAT functionality from the ISP side to the CPE, eliminating the need to implement carrier-grade NAT. This is accomplished by allocating a port range for a shared IPv4 address to each CPE. Moving the NAT functionality to the CPE allows the ISP to reduce the amount of state tracked for each subscriber, which improves the scalability of the translation infrastructure.

V4-via-v6 routing

''V4-via-v6'' routing is a technique where IPv4 addresses are assigned to end hosts only while intermediate routers are only assigned IPv6 addresses. IPv4 routes are propagated as usual, and no packet translation or encapsulation is employed, but use an IPv6 next hop. V4-via-v6 reduces the amount of management required, since the core network only needs to be assigned IPv6 addresses, but still requires that the core network be able to forward IPv4 packets. V4-via-v6 is defined for the

Border Gateway Protocol Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it make ...

(BGP) and the Babel routing protocol. It has been implemented the Bird Internet routing daemon and in ''babeld''.

Draft proposals

The following mechanisms are still being discussed or have been abandoned by the IETF:

4rd

IPv4 Residual Deployment (4rd) is an experimental mechanism to facilitate residual deployment of the IPv4 service across

networks. Like

6rd 6rd is a mechanism to facilitate IPv6 rapid deployment across IPv4 infrastructures of Internet service providers (ISPs). It is derived from 6to4, a preexisting mechanism to transfer IPv6 packets over the IPv4 network, with the significant chan ...

, it uses stateless address mappings between

and IPv4. It supports an extension of IPv4 addressing based on transport-layer ports. This is a stateless variant of the A+P model.

MAP

Mapping of Address and Port (MAP) is a

Cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...

IPv6 transition proposal which combines A+P port address translation with tunneling of the IPv4 packets over an ISP provider's internal

network. , MAP-T and MAP-E are proposed standards.

Deprecated mechanisms

These mechanisms have been deprecated by the IETF:

NAT-PT

''Network Address Translation/Protocol Translation'' (NAT-PT) is defined in RFC 2766, but due to numerous problems, it has been obsoleted by RFC 4966 and deprecated to historic status. It is typically used in conjunction with a DNS application-level gateway (DNS-ALG) implementation.

NAPT-PT

While almost identical to NAT-PT, ''Network Address Port Translation + Protocol Translation'', which is also described in RFC 2766, adds translation of the ports as well as the address. This is done primarily to avoid two hosts on one side of the mechanism from using the same exposed port on the other side of the mechanism, which could cause application instability and security flaws. This mechanism has been deprecated by RFC 4966.

Implementations

stone (software) In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition, and the way in which it is formed. Rocks ...

, port translator for Windows & Unix-based systems. * faithd, BSD-based static TRT implementation by the

KAME project The KAME project, a sub-project of the WIDE Project, was a joint effort of six organizations in Japan which aimed to provide a free IPv6 and IPsec (for both IPv4 and IPv6) protocol stack implementation for variants of the BSD Unix computer opera ...

CLATD
a CLAT / SIIT-DC Edge Relay implementation for Linux
WrapSix
a NAT64 implementation for Linux
TAYGA
a stateless NAT64 implementation for Linux
Jool
a stateful NAT64 implementation for Linux
naptd
user-level NAT-PT
Ecdysis
a NAT64 gateway, includes DNS64
Address Family Transition Router (AFTR)
a DS-Lite implementation
niit
Linux Kernel device that allow transmission of IPv4 unicast traffic through an IPv6 network
IVI
IPv4/IPv6 packet translation implementation as a Linux kernel(2.6 only) patch * Microsoft Forefront Unified Access Gateway, a reverse proxy and VPN solution that implements DNS64 and NAT64 *

BIND BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name daemon''), performs both of the main DNS server roles, acting as an authoritative ...

, Berkeley Internet Name Domain DNS server, implements DNS64 since version 9.8 *

PF (firewall) PF (Packet Filter, also written pf) is a BSD licensed stateful packet filter, a central piece of software for firewalling. It is comparable to netfilter (iptables), ipfw, and ipfilter. PF was developed for OpenBSD, but has been ported to ma ...

, the OpenBSD packet filter supports IP version translation since version 5.1, includes NAT64

References

*''IPv6 in Practice'', Benedikt Stockebrand (2006), *, ''Bump-in-the-Stack'' *, ''Bump-in-the-API'' *, ''Socks-based Gateway'' *, ''The China Education and Research Network (CERNET) IVI Translation Design and Deployment for the IPv4/IPv6 Coexistence and Transition''

External links

D. J. Bernstein - The IPv6 messTRT Howto from 2013IPv6 - Prospects and problems: a technical and management investigation into the deployment of IPv6Network World: Understanding Dual-Stack LiteIETF Draft: Framework for IPv4/IPv6 Translation

IPv4 and IPv6 Transition and Coexistence
6DEPLOY project, 2011
Assuring Interoperability Between Heterogeneous (IPv4/IPv6 Networks Without using Protocol Translation
IETE Technical Review, 2012
Configuring Hosts to Auto-detect (IPv6, IPv6-in-IPv4, or IPv4) Network Connectivity
KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS, 2011
IPv6: NAT-PT versus NAT64
Gianrico Fichera, 2012 {{DEFAULTSORT:Ipv6 Transition Mechanisms IPv6 Routing software