CCNA Cisco Certified Network Associate Study Guide - FTP Server

484 Chapter 10 � Wide Area Networking Protocols
It is important to understand that the PPP protocol stack is specified at the
Physical and Data Link layers only. NCP is used to allow communication of
multiple Network layer protocols by encapsulating the protocols across a
PPP data link.
You must know your PPP protocols!
Link Control Protocol (LCP) Configuration Options
Link Control Protocol offers PPP encapsulation different options, including
the following:
Authentication This option tells the calling side of the link to send information
that can identify the user. The two methods discussed in this
course are PAP and CHAP.
Compression This is used to increase the throughput of PPP connections.
PPP decompresses the data frame on the receiving end. Cisco uses
the Stacker and Predictor compression methods, discussed in the
Advanced Cisco Router Configuration course.
Error detection PPP uses Quality and Magic Number options to ensure
a reliable, loop-free data link.
Multilink Starting in IOS version 11.1, multilink is supported on PPP
links with Cisco routers. This splits the load for PPP over two or more
parallel circuits and is called a bundle.
PPP Session Establishment
PPP can be used with authentication. This means that communicating routers
must provide information to identify the link as a valid communication
link. When PPP connections are started, the links go through three phases of
session establishment:
Link-establishment phase LCP packets are sent by each PPP device to
configure and test the link. The LCP packets contain a field called the
Configuration Option that allows each device to see the size of the data,
compression, and authentication. If no Configuration Option field is
present, then the default configurations are used.