Simple Interface Transition

The Simple Interface Transition mechanism allows two remote IPv6 hosts to communicate by encapsulating IPv6 packets inside IPv4 packets.
Use of such tunnels can be either automatic or configured. In the IPv6-DRET implementation, the sit0 device is reserved for automatic tunneling, i.e. the destination of packets sent on this device is IPv4-compatible. ctX devices are configured individually with an end-point address.