Tunnelling are used
A tunneling protocol is one that encloses in its datagram another complete data packet that uses a different communications protocol. They essentially create a tunnel between two points on a network that can securely transmit any kind of data between them.
A tunneling protocol is a communications protocol that allows for the secure movement of data from one network to another. It involves allowing private network communications to be sent across a public network, such as the Internet, through a process called encapsulation.
Tunneling is used for source and destination hosts are on the same type of network.
There are different network in between them.
WAN are used between two LAN.