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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
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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 C02116)
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 0A16- Echo Reply- the response to the echo request message 0B16-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
Network Control Protocol • PPP-two ports negotiate not only the data link layer, but also the network layer