This section describes the principles of the Point-to-Point Protocol (PPP) and related protocols.

Point-to-point (P2P) connections are simple wide area network (WAN) connections. A P2P link uses PPP or High-Level Data Link Control (HDLC) as its link-layer protocol.

PPP, which works at the second layer (data link layer) of the open systems interconnection (OSI) model, is mainly used on links that support full-duplex to transmit data. PPP is widely used because it provides user authentication, supports synchronous and asynchronous communication, and is easy to extend.

PPP negotiation involves the following items:

• Data encapsulation mode: defines how to encapsulate multi-protocol data packets.

• Link Control Protocol (LCP): used to set up, monitor, and tear down data links.

• Network Control Protocol (NCP): used to negotiate options for a network layer protocol running atop PPP and the format and type of the data to be transmitted over data links.

PPP uses the Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) to secure network communication.

If carriers have high bandwidth requirements, bundle multiple PPP links into an MP link to increase link bandwidth and improve link reliability.