PPTPS : PPTP VPN Server
The Point-to-Point Tunnelling Protocol (PPTP) is a method for implementing virtual private networks. PPTP works by sending a regular PPP session to the peer with the Generic Routing Encapsulation (GRE) protocol. A second session on TCP port 1723 is used to initiate and manage the GRE session. PPTP is difficult to forward past a network firewall because it requires two network sessions. PPTP connections are authenticated with Microsoft MSCHAP-v2 or EAP-TLS. VPN traffic is optionally protected by MPPE encryption.