PPP over Ethernet (Tunneling) (PPPoE)
Point-to-Point Protocol over Ethernet (PPPoE) is a connection technology based on two proven standards: the PPP protocol and Ethernet. With this technology, which is offered by various service providers and Internet Service Providers( ISP), users of an Ethernet are connected to the Internet via a broadband connection area.
The connection technology can be based on a broadband radio technology, a broadband cable network, an xDSL technology or another technology used in the connection area. All users connected to the Ethernet share a common PPPoE connection. The method is mainly offered by ADSL providers.
PPPoE is often used in conjunction with ADSL. In this case, users are connected to the Ethernet via ADSL modems and can establish a dial-up connection from their computer to another Ethernet and are thus connected to it in a point-to-point connection. The key here is that Ethernet is packet-based and does not support mechanisms for circuit-based connections.
In the protocol hierarchy, PPPoE as an access method lies on the link layer between Ethernet and the Point to Point Protocol (PPP). The PPP data frames are encapsulated in the data field of the Ethernet frame. In normal point-to-point connections, two endpoints are connected via a leased line or, in the case of ATM, via a virtual circuit( VC). With Ethernet, however, any node can be connected to any other.
For this reason, PPPoE uses the MAC addresses of the source and destination nodes to ensure that the data packet reaches the destination node. This requires that the MAC addresses are known. This is done by PPoE discovery (PPPoED). If the MAC addresses are known and a session is created, then the endpoints can establish a point-to-point connection and exchange Ethernet packets over it.
PPPoE was developed by UUNET, Redback Networks and RouterWare and is described in RFC 2516.