The IPv6 over IPv4 (6to4) router connects IPv6 hosts or sites over the existing IPv4 Internet infrastructure.

RFCs for 6to4 are stored by the Internet Engineering Task Force (IETF).

For information on 6to4, see RFC 3056: Connection of IPv6 Domains via IPv4 Clouds and RFC 3068: An Anycast Prefix for 6to4 Relay Routers.

For Microsoft licensing information, see Published Protocols and Royalty-Free License on Microsoft Developer Network (MSDN).