1. 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
11. Data Link Control and Protocols - Lin
10/27/2004

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

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

15. 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

16. 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

17. Code Values for IPCP Packets01
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

18. 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

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