chapter 2 point-to-point protocol (ppp)

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Point-to-Point Protocol (PPP)

Accessing the WAN – Chapter 2

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Objectives Describe the fundamental concepts of point-to-point serial

communication including TDM, demarcation point, DTE-DCE functions, HDLC encapsulation, and serial interface troubleshooting.

Describe PPP concepts including PPP layered architecture, PPP frame structure, PPP session establishment, multiprotocol encapsulation support, link control protocol (LCP), network control protocol (NCP), and Internet Protocol Control Protocol (IPCP).

Configure PPP on a serial interface including enabling PPP encapsulation, verifying the PPP connection and troubleshooting encapsulation problems.

Configure PPP authentication including explaining PAP and CHAP authentication protocols, configuring PPP authentication using PAP and CHAP, and troubleshooting PPP authentication problems.

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Fundamental Concepts of Point-to-Point Serial Communication

Concept of serial communication as the basis of WAN technologies – Which is faster?

Eight data-carrying wires

to carry 8 bits – 1 byte

Two wires to carry 2 bits

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Serial Communication Standards

Serial connections commonly used – why?

•cost of cable and synchronization

•simpler wiring

•longer than parallel cables

•much less interaction (crosstalk)

There are three key serial communication standards

•RS-232 - pc to modem

•V.35 - modem-to-multiplexer - DSU

•HSSI - High-Speed Serial Interface – Token Ring

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RS-232

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Fundamental Concepts of Point-to-Point Serial Communication Htwo or more data streams are transported across a

single physical connection using TDM

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Fundamental Concepts of Point-to-Point Serial Communication Define the location of the demarcation point relative to

customer and service provider networks

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Fundamental Concepts of Point-to-Point Serial Communication Explain the terms DTE and DCE with relative to the

location of devices in a network

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Fundamental Concepts of Point-to-Point Serial Communication Describe how high-level data link control (HDLC) uses

one of three frame types to encapsulate data

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Fundamental Concepts of Point-to-Point Serial Communication Explain when and how to configure HDLC

encapsulation on a router

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Describe the Fundamental Concepts of Point-to-Point Serial Communication Describe the procedure to follow when troubleshooting

a serial connection

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Point-to-Point Concepts Describe PPP in terms of its use in WAN links

•The link quality management feature monitors the quality of the link. If too many errors are detected, PPP takes the link down.

•PPP supports PAP and CHAP authentication. This feature is explained and practiced in a later section.

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Point-to-Point Concepts Describe the general function of each layer of PPP

architecture

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Point-to-Point Concepts Describe the purpose and format of each of the fields in

a PPP frame

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Point-to-Point Concepts Define the three phases of PPP session establishment

LCP must first open the connection and negotiate

configuration options.

The LCP tests the link to determine whether the link quality is sufficient to bring up network layer protocols.

NCP can separately configure the network layer protocols, and

bring them up and take them down at any

time.

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Point-to-Point Concepts Explain the role of the LCP in PPP

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Point-to-Point Concepts Describe the characteristics of NCP

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Configure PPP on a Serial Interface Describe how configuration options are communicated

in the LCP frame

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Configure PPP on a Serial Interface Explain the purpose of the commands used to configure

and verify PPP connections

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Configure PPP on a Serial Interface Explain the output of the show interfaces serial

command

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Configure PPP on a Serial Interface Explain the output of the debug ppp command

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Configuring PPP with Authentication Differentiate between PAP and CHAP

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Configuring PPP with Authentication Describe how to use PAP to authenticate a PPP

connection

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Configuring PPP with Authentication Describe how to use CHAP to authenticate a PPP

connection

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Configuring PPP with Authentication Outline the PPP encapsulation and authentication

process on a flow chart

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Configuring PPP with Authentication Explain how to configure a PPP connection with

authentication

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Configuring PPP with Authentication Explain the output of the debug ppp authentication

command

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Summary

PPP is a widely used WAN protocol

PPP provides multi-protocol LAN to WAN connections

PPP session establishment – 4 phasesLink establishment

Link quality determination

Network layer protocol configuration negotiation

Link termination

WAN Encapsulation–HDLC default encapsulation

–PPP

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Summary

PPP authentication–PAP

•2 way handshake

–CHAP

•3 way handshake

–Use debug ppp authentication to confirm authentication configuration

PPP configuration–Done on a serial interface

After PPP configuration, use show interfaces command to display:

–LCP state

–NCP state

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