Point-to-Point Access: Chapter 12 Point-to-Point Access: (PPP)

11-7 POINT-TO-POINT PROTOCOL Several Data Link Protocols: PPP, HDLC… HDLC supports both - point-to-point configurations - multipoint configurations PPP supports only - point-to-point configurations - the simplest in the Data Link protocol family - Internet standard protocol defined in Internet Request-For-Comments (RFCs) 2153 and 1661

11-7 POINT-TO-POINT PROTOCOL PPP Provide point-to-point, router-to-router, host-to-router, host-to-host, host-to-ISP, and SONET/SDH connections Considered a peer technology based on its point-to-point physical configuration Commonly used over dial-up / DSL / or leased lines to provide connections into IP networks

Frame Format PPP is based on the High-Level Data Link Control (HDLC) protocol The difference between PPP frames and HDLC frames is that PPP frames contain protocol and Link Control Protocol (LCP) fields LCP Described in RFCs 1548, 1570, 1661, 2153, and 2484 Describes PPP organization and methodology, including basic LCP extensions CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

11-7 POINT-TO-POINT PROTOCOL PPP Internet standard protocol defined in Internet Request-For-Comments (RFCs) 2153 and 1661 Provide point-to-point, router-to-router, host-to-router, and host-to-host connections Considered a peer technology based on its point-to-point physical configuration Commonly used over dial-up or leased lines to provide connections into IP networks Serial Line Internet Protocol (SLIP) was the predecessor to PPP

PPP in the Protocol Stack CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

Transition states

PPP frame

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

Protocol Stack ชุดการทำงานต่างๆของ Protocol ถูกควบคุมและจัดการโดยผ่าน Frame format ต่างๆที่ถูกออกแบบไว้ Frame Header Packet Frame Trailer

Figure 11.34 Multiplexing in PPP

12.10 An example LCP: C02116 PAP: C02316 CHAP: C22316 IPCP: 802116 IPCP: 802116

Link Control Protocol (LCP)

LCP Packet Encapsulated in a Frame Frame Header LCP Packet

Table 12.1 LCP packets and their codes 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 0516 Terminate-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-request A 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

Table 12.2 Common options Maximum receive unit 1500 Default Maximum receive unit 1500 Authentication protocol None Protocol field compression Off Address and control field compression

Authentication Protocol

PAP packets Frame Header PAP packet

CHAP packets Frame Header CHAP packet

Network Protocol IPCP

IPCP packet encapsulated in PPP frame Frame Header IPCP packet

Table 12.3 Code value for IPCP packets 01 Configure-request 02 Configure-ack 03 Configure-nak 04 Configure-reject 05 Terminate-request 06 Terminate-ack 07 Code-reject

An example

An example (continued)