Point-to-Point Protocol over Ethernet [protocol] - (ADSL, RFC 2516)

The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating PPP frames inside Ethernet frames. It appeared at the turn of the century, in the context of the boom of the DSL as the solution for tunneling packets over the DSL connection to the ISP's IP network, and from there to the rest of the Internet.

A 2005 networking book noted that "Most DSL providers use PPPoE, which provides authentication, encryption and compression."

Typical use of PPPoE involves leveraging the PPP facilities for authenticating the user with a username and password, predominately via the PAP protocol and less often via CHAP.

Source: Point-to-point protocol over Ethernet