Layer 2 Tunneling Protocol - Wikipedia
https://en.wikipedia.org/wiki/Layer_2_Tunneling_Protocol
In computer networking, Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. It uses encryption ('hiding') only for its own control messages (using an optional pre-shared secret)...
Manual:Interface/L2TP - MikroTik Wiki
https://wiki.mikrotik.com/wiki/Manual:Interface/L2TP
L2TP is a secure tunnel protocol for transporting IP traffic using PPP. L2TP encapsulates PPP in virtual lines that run over IP, Frame Relay and other protocols (that are not currently supported by...