L2TP and PPTP

Layer Two Tunneling Protocol (L2TP) and Point-to-Point Tunneling Protocol (PPTP) are both OSI layer two tunneling protocols. Tunneling is the encapsulation of one packet within another, which allows you to hide the original packet from view or change the nature of the network transport. This can be done for both security and practical reasons.

From a practical perspective, assume that you are using TCP/IP to communicate between two machines. Your message may pass over various networks, such as an Asynchronous Transfer Mode (ATM) network, as it moves from source to destination. As the ATM protocol can neither read nor understand TCP/IP packets, something must be done to make them passable across the network. By encapsulating a packet ...

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