C H A P T E R 13
• Describe the development of PPP.
• Describe the components of PPP and how they operate.
• Provide a summary of the basic protocol elements and operations of PPP.
The Point-to-Point Protocol (PPP) originally emerged as an encapsulation protocol for transporting IP
traffic over point-to-point links. PPP also established a standard for the assignment and management of
IP addresses, asynchronous (start/stop) and bit-oriented synchronous encapsulation, network protocol
multiplexing, link configuration, link quality testing, error detection, and option negotiation for such
capabilities as network layer address negotiation and data-compression negotiation. PPP supports these
functions by providing an extensible Link Control Protocol (LCP) and a family of Network Control
Protocols (NCPs) to negotiate optional configuration parameters and facilities. In addition to IP, PPP
supports other protocols, including Novell's Internetwork Packet Exchange (IPX) and DECnet.
PPP provides a method for transmitting datagrams over serial point-to-point links. PPP contains three
• A method for encapsulating datagrams over serial links. PPP uses the High-Level Data Link Control
(HDLC) protocol as a basis for encapsulating datagrams over point-to-point links. (See Chapter 16,
“Synchronous Data Link Control and Derivatives,” for more information on HDLC.)
• An extensible LCP to establish, configure, and test the data link connection.
• A family of NCPs for establishing and configuring different network layer protocols. PPP is
designed to allow the simultaneous use of multiple network layer protocols.
rnetworking Technologies Handbook
To establish communications over a point-to-point link, the originating PPP first sends LCP frames to
configure and (optionally) test the data link. After the link has been established and optional facil