12. Point-to-Point Access: PPP CPET/ECET 355 12. Point-to-Point Access: PPP Data Communications and Networking Fall 2004 Professor Paul I-Hai Lin Electrical and Computer Engineering Technology Indiana University-Purdue University Fort Wayne www.ecet.ipfw.edu/~lin 11. Data Link Control and Protocols - Lin 10/27/2004

Point-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 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – 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 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – Transition States Idle, Establishing, Authenticating, Networking, Terminating From p. 296, Figure 12.2 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – 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 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – 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 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – LCP Packets 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 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 From p. 298, Table 12.1 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – LCP Packets Configuration Packets Link Termination Packets Configuration-request Configuration-ack Configuration-nak Configuration-reject Link Termination Packets Termination-request Termination-ack 11. Data Link Control and Protocols - Lin 10/27/2004

PPP – LCP Packets Link Monitoring and Debugging Packets Code-reject Protocol-reject Echo-request Echo-reply Discard-request Options (in the info field) 11. Data Link Control and Protocols - Lin 10/27/2004

LCP Packet Option Maximum receive unit 1500 Authentication protocol Default Maximum receive unit 1500 Authentication protocol None Protocol field compression Off Address and control field compression From p. 298, Figure 12.4 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

Authentication 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 11. Data Link Control and Protocols - Lin 10/27/2004

PAP (Password Authentication) From p. 300, Figure 12.5 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

PAP Packets From p. 301, Figure 12.6 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

CHAP From p. 302, Figure 12.7 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

CHAP Packets From p. 302, Figure 12.8 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

Network Control Protocol (NCP) IPCP: Internetwork Protocol Control Protocol From p. 303, Figure 12.9 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

Code Values for IPCP Packets 01 Configure-request 02 Configure-ack 03 Configure-nak 04 Configure-reject 05 Terminate-request 06 Terminate-ack 07 Code-reject From p. 303, Table 12.3 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

PPP Connection Example From p. 303, Figure 12.9 of Data Communications and Networking, Forouzan, McGrawHill 11. Data Link Control and Protocols - Lin 10/27/2004

Summary Questions? 11. Data Link Control and Protocols - Lin 10/27/2004