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CPET/ECET 355CPET/ECET 35512. Point-to-Point Access:

PPP

Data Communications and NetworkingFall 2004

Professor Paul I-Hai LinElectrical and Computer Engineering TechnologyIndiana University-Purdue University Fort Wayne

www.ecet.ipfw.edu/~lin

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Point-to-Point Access: PPPPoint-to-Point Access: PPP

Data Link Protocol for– Dial-up modems– DSL modems– Cable modems

PPP Defines– Frame format– Negotiate and establish exchange of data– Encapsulation of network layer data– Authentication

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PPP – Frame FormatPPP – Frame Format

Address Field Control Field Protocol Field Data Field Frame Check Sequence (FCS)

From p. 296, Figure 12.1 of Data Communications and Networking, Forouzan, McGrawHill

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PPP – Transition StatesPPP – Transition States Idle, Establishing, Authenticating,

Networking, Terminating

From p. 296, Figure 12.2 of Data Communications and Networking, Forouzan, McGrawHill

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PPP – StackPPP – Stack Three Protocols

– Link Control protocol– Authentication protocol, and – Network Control protocol

From p. 297, Figure 12.3 of Data Communications and Networking, Forouzan, McGrawHill

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PPP – Link Control ProtocolPPP – Link Control Protocol LCP Responsibilities

– Establishing, Maintaining, Configuring, and Terminating Links

– Payload: Code, ID, Length, Information Fields

From p. 298, Figure 12.4 of Data Communications and Networking, Forouzan, McGrawHill

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PPP – LCP PacketsPPP – LCP Packets

From p. 298, Table 12.1 of Data Communications and Networking, Forouzan, McGrawHill

Code Packet Type Description

0116 Configure-request Contains the list of proposed options and their values

0216 Configure-ack Accepts all options proposed

0316 Configure-nak Announces that some options are not acceptable

0416 Configure-reject Announces that some options are not recognized

0516Terminate-request Requests to shut down the line

0616 Terminate-ack Accepts the shut down request

0716 Code-reject Announces an unknown code

0816 Protocol-reject Announces an unknown protocol

0916 Echo-requestA type of hello message to check if the other end is alive

0A16 Echo-reply The response to the echo-request message

0B16 Discard-request A request to discard the packet

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PPP – LCP PacketsPPP – LCP Packets

Configuration Packets– Configuration-request– Configuration-ack– Configuration-nak– Configuration-reject

Link Termination Packets– Termination-request– Termination-ack

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PPP – LCP PacketsPPP – LCP Packets

Link Monitoring and Debugging Packets– Code-reject– Protocol-reject– Echo-request– Echo-reply– Discard-request

Options (in the info field)

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LCP Packet OptionLCP Packet Option

From p. 298, Figure 12.4 of Data Communications and Networking, Forouzan, McGrawHill

Option Default

Maximum receive unit 1500

Authentication protocol None

Protocol field compression Off

Address and control field compression Off

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Authentication ProtocolsAuthentication Protocols Password Authentication Protocols

(PAP)– User sends ID (user name), and Password– System checks the validity: accept, or reject

Challenge Handshake Authentication Protocols (CHAP) – System send a challenge packet– The user applies a predefined function, and

reply the challenge packet– The system does the same to see if the

same result can be obtained: accept or reject

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PAP (Password Authentication)PAP (Password Authentication)

From p. 300, Figure 12.5 of Data Communications and Networking, Forouzan, McGrawHill

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PAP PacketsPAP Packets

From p. 301, Figure 12.6 of Data Communications and Networking, Forouzan, McGrawHill

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CHAP CHAP

From p. 302, Figure 12.7 of Data Communications and Networking, Forouzan, McGrawHill

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CHAP PacketsCHAP Packets

From p. 302, Figure 12.8 of Data Communications and Networking, Forouzan, McGrawHill

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Network Control Protocol (NCP)Network Control Protocol (NCP)

From p. 303, Figure 12.9 of Data Communications and Networking, Forouzan, McGrawHill

IPCP: Internetwork Protocol Control Protocol

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Code Values for IPCP PacketsCode Values for IPCP Packets

From p. 303, Table 12.3 of Data Communications and Networking, Forouzan, McGrawHill

Code IPCP Packet

01 Configure-request

02 Configure-ack

03 Configure-nak

04 Configure-reject

05 Terminate-request

06 Terminate-ack

07 Code-reject

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PPP Connection ExamplePPP Connection Example

From p. 303, Figure 12.9 of Data Communications and Networking, Forouzan, McGrawHill

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SummarySummary

Questions?