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

2. 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

3. 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

4. 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

5. CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

6. 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

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

8. Transition states

9. PPP frame

10. 12.2 PPP Stack Link Control Protocol (LCP) Authentication Protocols
Network Control Protocol (NCP)
Bit Padding
Digital Signals (DS) Services

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

12. Figure 11.34 Multiplexing in PPP

13. An example
LCP: C02116
PAP: C02316
CHAP: C22316
IPCP:
IPCP:

14. Link Control Protocol (LCP)

15. LCP Packet Encapsulated in a Frame
Frame Header
LCP Packet

16. 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

17. 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

18. Authentication Protocol

19. PAP packets
Frame Header
PAP packet

20. CHAP packets
Frame Header
CHAP packet

21. Network Protocol
IPCP

22. IPCP packet encapsulated in PPP frame
Frame Header
IPCP packet

23. Table 12.3 Code value for IPCP packets01
Configure-request 02
Configure-ack 03
Configure-nak 04
Configure-reject 05
Terminate-request 06
Terminate-ack 07
Code-reject

24. An example

25. An example (continued)