It is the responsibility of each protocol to distinguish padding octets from real information. After the link has been established, the peer MAY be authenticated. Then, PPP MUST send NCP packets to choose and configure one or more network-layer protocols. This diagram is not a complete representation of the automaton. Implementation MUST be done by consulting the actual state transition table.
Events are in upper case.
Actions are in lower case. For these purposes, the state machine is initially in the Closed state. Once the Opened state has been reached, both ends of the link have met the requirement of having both sent and received a Configure-Ack packet.