A PPP connection goes through phases which can be shown in a transition phase .
Dead: In the dead phase the link is not being used. There is no active carrier at the physical layer and the line is quiet.
Establish : When one of the nodes starts the communication the connections goes into this phase in this phase options are negotiated between the two parties. If the negotiation is successful the system goes to the authentication phase( if authentication is required) r directly to the networking phase. The link control protocols packets discussed shortly are used for this purpose. Several packets may be exchanged here.
Authenticate: The authentication phase is optional the two nodes may decide during the establishment phase not to skip this phase. However if they decide to proceed with authentication they send several authentication packets it goes to the termination phase.
Network : In the network phase negotiation for the network layer protocols takes place PPP specifies that two can be exchanged. The reason is that PPP supports multiple protocols at the network layer. If a node is running multiple protocols simultaneously at the network layer the receiving node to know which protocols will receive at the data.
Open: In the phase data transfer takes place. When a connection reaches this phase the exchange of data packets can be started. The connection remains in this phase until one of the end points wants to terminate the connection.
Terminate : In the termination phase the connection is terminated. Several packets are exchanged between the two ends for house cleaning and closing the link.