PPPoX (PPP over X) designates a family of encapsulating communications protocols implementing Point-to-Point Protocol. Specific implementations:
PPPoE: PPP over Ethernet – which can use 802.1q VLANs PPPoA: PPP over ATM PPTP: PPP encapsulated over GRE with a parallel control connection and some optional encryption L2TP v2 (and its ancestor L2F): PPP sessions multiplexed within tunnels and transported over UDP
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