Introduction

PPP (Point-to-Point Protocol) provides a standard method for transporting multiprotocol datagrams over point-to-point links. In the context of a network application, PPP allows IP datagrams to be exchanged with a node at the other end of a point-to-point link. Typically, a client will initiate a PPP connection by using a modem to dial into a foreign server through the public telephone system. However, PPP is also used in environments where the physical medium is not always point-to-point. One such example is Ethernet. The PPPoE and L2TP protocols enable support for transmission of PPP packets over Ethernet.

A PPP implementation may include support for a PPP client and a PPP server, perhaps even being utilized as both at the same time. Applications only have to be aware that PPP is being used as the underlying link-layer driver when establishing and breaking the physical link that is, during dial-up and hang up. In all other respects, the application is not aware that PPP is the low-level driver being used.