Apple Training Series: Mac OS X Support Essentials v10.6: A Guide to Supporting and Troubleshooting Mac OS X v10.6 Snow Leopard

This is a specification for connecting users on an Ethernet network to the Internet via a gateway, such as cable or DSL modems and wireless devices.

PPPoE users share a common connectionthey're supported by Ethernet in a LAN (multiuser) combined with PPP (serial connections).

PPPoE can be enabled in Network preferences.

Resources for PPPoE are found in /System/Library.