PPP Protocol PPP Stack -Establish a link (Link Control Protocol) -Authenticate Parties involved (Authentication Protocols) -Carry Network Layer (Network.
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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 C021 16 )
LCP Packet codes 01 16 - Configure request List of proposed options & values 02 16 - Configure acknowledgement- accepts all options proposed 03 16 - Configure negative acknowledgement announces that some options are acceptable 04 16 - Configure Reject Announces that some options are not recognizable 05 16 - Terminate Request-Request to shut down the line 06 16 - Terminate Acknowledgement Accepts the shut down request.
LCP Packet Codes (cont) 07 16 -Code Reject Announcing an unknown code 08 16 -Protocol Reject Announcing an unknown Protocol 09 16 - 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.
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