Point to Point Protocol over Ethernet

Point To Point Protocol over Ethernet (PPPoE)

The working standard for the PPPoE protocol was published by the IETF in 1999. The IETF specification for PPPoE is RFC 2516. PPPoE expands the original capability of PPP by allowing a virtual point to point connection over a multipoint Ethernet network architecture. PPPoE is a protocol that is widely used by ISPs to provision digital subscriber line (DSL) high speed Internet services, of which the most popular service is ADSL. The similarity between PPPoE and PPP has led to the widespread adoption of PPPoE as the preferred protocol for implementing high speed Internet access. Service providers can use the same authentication server for both PPP and PPPoE sessions, resulting in a cost savings. PPPoE uses standard methods of encryption, authentication, and compression specified by PPP.

PPPoE is configured as a point to point connection between two Ethernet ports. As a tunneling protocol, PPPoE is used as an effective foundation for the transport of IP packets at the network layer. IP is overlaid over a PPP connection and uses PPP as a virtual dial up connection between points on the network. From the user's perspective, a PPPoE session is initiated by using connection software on the client machine or router. PPPoE session initiation involves the identification of the Media Access Control (MAC) address of the remote device. This process, also known as PPPoE discovery, involves the following steps:

Initiation - The client software sends a PPPoE Active Discovery Initiation (PADI) packet to the server to intitiate the session.

1. Offer - The server responds with a PPPoE Active Discovery Offer (PADO) packet.
2. Request - Upon receipt of the PADO packet, the client responds by sending a PPPoE Active Discovery Request (PADR) packet to the server.
3. Confirmation - Upon receipt of the PADR packet, the server responds by generating a unique ID for the PPP session and sends it in a PPPoE Active Discovery Session (PADS) confirmation packet to the client.

When a PPPoE session is initiated, the destination IP address is only used when the session is active. The IP address is released after the session is closed, allowing for efficient re-use of IP addresses.