In the voluntary tunnel model, a tunnel is created by the user, typically by the use of a Layer Two Tunneling Protocol (L2TP)-enabled client.
As a result, the user sends L2TP packets to the Internet service provider (ISP), which forwards them on to the L2TP network server (LNS). In voluntary tunneling the ISP does not need to support L2TP, and the L2TP tunnel initiator is on the same system as the remote client. In this model, the tunnel extends across the entire Point-to-Point Protocol (PPP) session from the L2TP client to the LNS.