The document discusses point-to-point protocol (PPP) which establishes connections over telephone lines and digital subscriber lines. PPP uses a link control protocol (LCP) to establish, configure, and test the data link connection. LCP packets include configure-request, configure-ack and configure-nak. Authentication protocols like PAP and CHAP are used for authentication, and network control protocols like IPCP are used to configure network layer options.

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

2. 12.1 Point-To-Point Protocol Frame Format Transition States

3. 12.1 PPP frame

4. 12.2 Transition states

5. 12.2 PPP Stack Link Control Protocol (LCP) Authentication Protocols Network Control Protocol (NCP) Bit Padding Digital Signals (DS) Services

6. 12.3 Protocol stack

7. 12.4 LCP packet encapsulated in a frame

8. Table 12.1 LCP packets and their codes The response to the echo-request message Echo-reply 0A 16 A request to discard the packet Discard-request 0B 16 Announces an unknown code Code-reject 07 16 Announces an unknown protocol Protocol-reject 08 16 A type of hello message to check if the other end is alive Echo-request 09 16 Announces that some options are not recognized Configure-reject 04 16 Requests to shut down the line Terminate-request 05 16 Accepts the shut down request Terminate-ack 06 16 Announces that some options are not acceptable Configure-nak 03 16 Accepts all options proposed Configure-ack 02 16 Configure-request Packet Type Contains the list of proposed options and their values 01 16 Description Code

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

10. 12.5 PAP

11. 12.6 PAP packets

12. 12.7 CHAP

13. 12.8 CHAP packets

14. 12.9 IPCP packet encapsulated in PPP frame

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

16. 12.10 An example