Virtual private network technology runs on the idea of tunnelling. It establishes and maintains a logical network connection. The data from the system is converted and compiled into packets using a certain VPN protocol format. These packets are then encapsulated within some carrier protocol or base which is then transmitted flanked by VPN client and server. In the internet based virtual private networks the protocols are encapsulates within IP packets only. VPN undergoes protocol based formatting of data into packets to support authentication and encryption of the tunnels to secure them from any virtual threat.
VPN services are based upon the principle of tunneling. There are two types of tunneling, like voluntary and compulsory tunneling. Under the task of tunneling the VPN protocol builds and maintains a logical network connection of the systems using the network at any given point in time. VPN front end processor or we can call it point of presence server represent the logic built in broker device used under the compulsory tunneling process to authenticate and associate the client with the VPN servers. Under compulsory tunneling the details of VPN server connectivity would be hidden from its clients. This way the whole management control is easily transferred to the ISP over the tunnels. In order to attain the total management control the service providers have to install and maintain FEP devices also, which increases their work load for sure.
The L2TP is actually a combination of L2F and PPT protocols for VPN tunneling.L2F was initially created by Cisco. But later on it was combined with the very popular PPTP to create a better resolution for VPN tunneling. Both PPTP and L2TP exist at the layer two, or data link layer of the OSI model.
In order to find the VPN protocol you are looking for simply search through the VPN providers list.