- A protocol called link control protocol (LCP) runs on top of PPP and is a part of PPP functions. It configures the interfaces on each end of the connection. LCP provides automatic configuration for many features like magic numbers, datagram size and selecting optional authentication. Other options for configuration include extensible authentication protocol (EAP), password authentication protocol (PAP) and challenge handshake protocol (CHAP). CHAP is the usually method of authenticating with dial-up Internet providers.
- PPP allows multiple protocols to be used on the same network connection by providing a way for them to be encapsulated and configured. For each individual separate protocol used over the connection, there is a new network control protocol (NCP) provided to negotiate the configurations for the protocol.
- PPP includes a feature called 'magic numbers' to detect looped connections. When an LCP packet or message is sent, it can include a magic number. If the machine receives its own magic number in return instead of the other machines, it can recognize that the line is looped back and not reaching the desired network node.
- The three important parts of PPP are the LCP, which is responsible for starting and stopping the connections and allowing the nodes to negotiate the different options available; the NCP, which performs the actual negotiation of options like encryption, compression and network address; and finally, the multi-link PPP, which is the actual payload of information that is transferred.
- There are five phases of the PPP: Link Dead is the phase after one side hangs up or disconnects; Link Establishment is when the LCP negotiates for options; Authentication, which is optional and happens before any connection is established; Network Layer Protocol is when each protocol that will be used is started and Link Termination, when the connection fails or the nodes chose to disconnect.
