NAT64 is an

IPv6 transition mechanism An IPv6 transition mechanism is a technology that facilitates the transitioning of the Internet from the Internet Protocol version 4 (IPv4) infrastructure in use since 1983 to the successor addressing and routing system of Internet Protocol Vers ...

that facilitates communication between

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

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 needs at least one IPv4 address and an IPv6 network segment comprising a 32-bit address space. The "well-known prefix" reserved for this service is . An IPv6 client embeds the IPv4 address it wishes to communicate with using the host part of the IPv6 network segment, resulting in an ''IPv4-embedded IPv6 addresses'' (hence the 32-bit address space in the IPv6 network segment), and sends packets to the resulting address. The NAT64 gateway creates a mapping between the IPv6 and the IPv4 addresses, which may be manually configured or determined automatically.

Principle of operation

A simple NAT64 installation may consist of a gateway with two interfaces connected to an IPv4 network and an IPv6 network, respectively. Traffic from the IPv6 network is routed via the gateway which performs all the necessary translations for transferring packets between the two networks. However, the translation is not symmetric, as the

IPv6 address An Internet Protocol Version 6 address (IPv6 address) is a numeric label that is used to identify and locate a network interface of a computer or a network node participating in a computer network using IPv6. IP addresses are included in the ...

space is much larger than the

IPv4 address 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 d ...

space; thus, one-to-one address mapping is not possible. The gateway maintains IPv6-to-IPv4 address mapping, which may be established with an automatic algorithm (stateless mapping) or with special and manual translations (stateful mapping) when the first packet from the IPv6 network reaches the NAT64 gateway. Stateless translation is appropriate when a NAT64 translator is used in front of IPv4-only servers to allow them to be reached by remote IPv6-only clients. Stateful translation is suitable for deployment at the client side or at the service provider, allowing IPv6-only client hosts to reach remote IPv4-only nodes. In general, NAT64 is designed to be used when the communication is initiated by IPv6 hosts. Some mechanisms, including static address mapping, exist to allow the inverse scenario. Not every type of resource is accessible with NAT64. Protocols that embed IPv4 literal addresses, such as SIP and SDP,

FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data ...

WebSocket WebSocket is a computer communications protocol, providing full-duplex communication channels over a single TCP connection. The WebSocket protocol was standardized by the IETF as in 2011. The current API specification allowing web applications ...

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, deb ...

, MSN, and any other content with IPv4 literals are excluded, but a dual-stacked

web proxy In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. Instead of connecting directly to a server that can fulfill a request ...

allows IPv6-only clients to access even web pages with IPv4 literals in URLs. However,

464XLAT An IPv6 transition mechanism is a technology that facilitates the IPv6 deployment, transitioning of the Internet from the IPv4, Internet Protocol version 4 (IPv4) infrastructure in use since 1983 to the successor addressing and routing system of ...

, which uses NAT64, allows use of such protocols over IPv6-only connections. For SIP and FTP, the problem can also be solved using an

application-level gateway An application-level gateway (ALG, also known as application layer gateway, application gateway, application proxy, or application-level proxy) is a security component that augments a firewall or NAT employed in a computer network. It allows cust ...

, or using Port Control Protocol with the PREFIX64 extension.

Implementations

* Cisco (2010 stateless, 2011 statefull) * Juniper (2010)

References

{{IPv6 Routing software IPv6 transition technologies