Point-to-Point Tunneling Protocol
The Point-to-Point Tunneling Protocol (PPTP) is a Layer 2 protocol that encapsulates PPP frames in IP datagrams for transmission over the Internet. PPTP can be used for remote access and router-to-router VPN connections. It uses a TCP connection for tunnel maintenance and a modified version of GRE to encapsulate PPP frames for tunneled data. The payloads of the encapsulated PPP frames can be encrypted/compressed. Figure 24.5 shows the structure of a PPTP packet containing user data.
Figure 24.5. Structure of the PPTP packet.
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