In the process of configuring, maintaining and terminating the point-to-point link, the PPP link goes through several distinct phases which are specified in the following simplified state diagram:
+------+ +-----------+ +--------------+
| | UP | | OPENED | | SUCCESS/NONE
| Dead |------->| Establish |---------->| Authenticate |--+
| | | | | | |
+------+ +-----------+ +--------------+ |
^ | | |
| FAIL | FAIL | |
+<--------------+ +----------+ |
| | |
| +-----------+ | +---------+ |
| DOWN | | | CLOSING | | |
+------------| Terminate |<---+<----------| Network |<-+
| | | |
+-----------+ +---------+
Not all transitions are specified in this diagram. The following semantics MUST be followed.