PPP Protocol PPP Stack Establish a link Link

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 02116)

LCP Packet codes 0116 - Configure request List of proposed options & values 0216 - Configure acknowledgement- accepts all options proposed 0316 - Configure negative acknowledgement announces that some options are acceptable 0416 - Configure Reject Announces that some options are not recognizable 0516 - Terminate Request-Request to shut down the line 0616 - Terminate Acknowledgement Accepts the shut down request.

LCP Packet Codes (cont) 0716 -Code Reject Announcing an unknown code 0816 -Protocol Reject Announcing an unknown Protocol 0916 - Echo Request-A type of hello message to see if the other end is alive 0 A 16 - Echo Reply- the response to the echo request message 0 B 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 01 Configure Request 02 Configure-ack 03 Configure-nak 04 Configure-Reject 05 Terminate Request 06 Terminate –ack 07 Code Reject