Ccna routing and Switching Complete Study Guide

EIA/TIA-232-C, V.24, V.35, and ISDN    A Physical layer international standard for serial 

communication.

HDLC    A method for encapsulating datagrams over serial links.

LCP    A method of establishing, configuring, maintaining, and terminating the point-to-

point connection. It also provides features such as authentication. I’ll give you a complete 

list of these features in the next section.

NCP    NCP is a method of establishing and configuring different Network layer protocols 

for transport across the PPP link. NCP is designed to allow the simultaneous use of multi-

ple Network layer protocols. Two examples of protocols here are Internet Protocol Control 

Protocol (IPCP) and Cisco Discovery Protocol Control Protocol (CDPCP).

Burn it into your mind 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 identifying and encapsulating the protocols across a PPP data link.

Remember that if you have a Cisco router and a non-Cisco router connected 

with a serial connection, you must configure PPP or another encapsulation 

method like Frame Relay because the HDLC default just won’t work!

Next, we’ll cover the options for LCP and PPP session establishment.