IPv6 over IPv4 tunneling

For outgoing data, IPv6 packets are encapsulated into IPv4 packets in border router. Then, these packets are sent through IPv4 to a server (tunnel broker) that does decapsulation and forwarding of IPv6 packets to the Internet.

For ingoing data, the tunnel broker is responsable of encapsulating IPv6 into IPv4, and the border router is in charge of decapsulating packets.

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There's an implementation of 6in4 in Akaros' Plan9 (UC Berkeley), available at Plan9's github . The chosen tunnel broker is Hurricane Electric Internet Service