PPP Protocol PPP Stack -Establish a link (Link Control Protocol) -Authenticate Parties involved (Authentication Protocols) -Carry Network Layer (Network Control Protocol)

Link Control Protocol (LCP) Establishing a link Maintaining a link Configuring a link Terminating links Negotiate between the two endpoints –Both sides must reach an agreement about the options before the link can be established\ When carrying a LCP, we are either establishing a link or terminating a link. No data is included in the frame.

Code-defines the type of LCP Packet ID-Holds a value to match and request with the reply one endpoint inserts a value in this field which will be copied in the reply packet Length-defines the length of the entire LCP packet Information-extra info for some LCP packets (Protocol Field contains the value C )

LCP Packet codes Configure request List of proposed options & values Configure acknowledgement- accepts all options proposed Configure negative acknowledgement announces that some options are acceptable Configure Reject Announces that some options are not recognizable Terminate Request-Request to shut down the line Terminate Acknowledgement Accepts the shut down request.

LCP Packet Codes (cont) Code Reject Announcing an unknown code Protocol Reject Announcing an unknown Protocol Echo Request-A type of hello message to see if the other end is alive 0A 16 - Echo Reply- the response to the echo request message 0B 16 -Discard Request-A Request to discard the packet.

LCP Packets Configuration packets- Negotiate options between ends Configure Request-Endpoint wanting to start a connection Configure Acknowledgement-if all options listed by request package are accepted Configure Negative Acknowledgement-if receiver of the request packet recognizes all the option, but finds some need to omit or revise Configure Reject-If some of the options are not recognizable by the receiving party

LCP Packets Link Termination Protocols Terminate Request Terminate acknowledgement

LCP Link Monitoring and Debugging Packets Code Reject-unrecognizable code Protocol Reject-unrecognizable protocol Echo request-Packet is sent to monitor the link Echo Reply-Packet is sent in response to an Echo Discard Request-loop back test by sender

LCP Packet Options Options negotiated between to end points are inserted into the information field –Maximum receive unit –Authentication –Protocol field compression –Address and control field compression

Authentication Protocols PAP-Password Authentication Protocol –User sends username and password –System checks validity of the identification and password and either accepts or denies the connection.

PAP Packets

CHAP-Challenge Handshake Authentication protocol Predefined function System sends a user a challenge packet User applies function to challenge value Apply function to password and send System applies function to password to verify or deny

CHAP Frames

Network Control Protocol PPP-two ports negotiate not only the data link layer, but also the network layer

Internetwork Protocol Control Protocol Code 01Configure Request 02Configure-ack 03Configure-nak 04Configure-Reject 05Terminate Request 06Terminate –ack 07Code Reject