Point-to-Point Protocol (PPP)

ผศ.ดร. อนั�นัต์ ผลเพิ่ �มAsst.Prof.Anan Phonphoem, Ph.D.

anan@cpe.ku.ac.thhttp://www.cpe.ku.ac.th/~anan

Computer Engineering DepartmentKasetsart University, Bangkok, Thailand

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Point-to-Point Protocol

Internet

ISP

Many Internet users connect from home• Dial-up (Telephone line)• Leased line

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PPP Transition states

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PPP Layers

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PPP Layers

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PPP Layers (stacks) Link Control Protocol (LCP) Authentication Protocols Network Control Protocol (NCP) Bit Padding Digital Signals (DS) Services

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PPP Frame

Address: broadcast (avoid data link address)Control: U-frame format (HDLC)Protocol: defines data field

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Link Control Protocol (LCP)• establish/terminate• maintain• configuration

Code: 01=Config-request 02=Config-ack 05=Terminate-req …

Link Control Protocol (LCP)

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Common Options

Option Default

Maximum receive unit 1500

Authentication protocol None

Protocol field compression Off

Address and control field compression Off

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Authentication Mostly PPP is dial-up user. Validating the user is important Password Authentication Protocol (PAP)

2-way handshake Less secure

Challenge Handshake Authentication Protocol (CHAP) 3-way handshake More secure (no password sent)

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Password Authentication Protocol (PAP)

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PAP Packets

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Challenge Handshake Authentication Protocol (CHAP)

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CHAP packets

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PPP Transition states

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Internetwork Protocol Control Protocol (IPCP)

• Establish / Terminate @ network layer connection (IP)• Code 01:Configure-request 02:Configure-ack …

PPP communication

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PPP configuration

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PPP configuration

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Lab 3.3.2 PPP encapsulation 3.3.3 PPP authentication 3.3.5 Troubleshooting PPP