PPP Overview and Architecture

PPP is documented in RFC 1661 as a standard method for transporting multiple protocols over
point-to-point links. PPP substantially improved upon the Serial Line Internet Protocol (SLIP).
SLIP transports IP packets only across serial circuits.

NOTE:Although beyond the scope of this Study Guide, PPP has evolved to operate
over Ethernet (PPPoE), as specified in RFC 2516, and over ATM (PPPoA), as
specified in RFC 2364. Packet over SONET (Synchronous Optical Network) also
uses PPP-based encapsulations. One of these options may well be implemented
in an ADSL (asymmetrical digital subscriber line) solution from some
service providers.

PPP contains three main components:

The encapsulation method used, and for PPP the default is an HDLC-like framing.

Link Control Protocol (LCP)
is used when establishing, configuring, and testing the datalink
connection.

A family of
Network Control Protocols (NCPs)
, which establishes and configures different
Network layer protocols. PPP, LCP, and NCP are all considered layer 2 protocols.