In the compulsory tunnel model - remote dial, the home gateway (L2TP network server (LNS)) initiates a tunnel to an Internet service provider (ISP) (LAC) and instructs the ISP to place a local call to the Point-to-Point Protocol (PPP) answer client.
This model is intended for cases where the remote PPP answer client has a permanent, established telephone number with an ISP. This model is expected to be used when a company with established presence on the Internet needs to establish a connection to a remote office that requires a dial-up link. In this model, the tunnel only extends across the segment of the PPP session between the LNS and the ISP.