Slide 14 of 27
Request for Comments (RFC) 2516 describes a protocol called the Point-to-Point Protocol over Ethernet (PPPoE). Designed specifically for ADSL, PPPoE defines a way to encapsulate an IP packet in a PPP frame that is transported over the Ethernet protocol. The general idea of PPPoE is to be able to extend an Ethernet network logically across bridging devices such as the ADSL modem and telco's access concentrator. It also provides a mechanism to logically disconnect a host from the Internet during periods of idleness; this is the best protection that a provider can offer a customer. When the user points the browser to a URL or when the user's e-mail client tries to access the Internet to check mail, PPP procedures re-establish the logical connection. This entire operation is fast because the physical connection is still intact and is transparent to the end user.
RFC 2516 can be found at ftp://ftp.isi.edu/in-notesrfc2516.txt or via the RFC Editor's Web site (http://www.rfc-editor.org).