PPP Line Activation and Phases
The phases of the Point to Point Protocol according to RFC 1661 are listed below:
- Link Dead. This phase occurs when the link fails, or one side has been told to disconnect (e.g. a user has finished his or her dialup connection.)
- Link Establishment Phase. This phase is where Link Control Protocol negotiation is attempted. If successful, control goes either to the authentication phase or the Network-Layer Protocol phase, depending on whether authentication is desired.
- Authentication Phase. This phase is optional. It allows the sides to authenticate each other before a connection is established. If successful, control goes to the network-layer protocol phase.
- Network-Layer Protocol Phase. This phase is where each desired protocols' Network Control Protocols are invoked. For example, IPCP is used in establishing IP service over the line. Data transport for all protocols which are successfully started with their network control protocols also occurs in this phase. Closing down of network protocols also occur in this phase.
- Link Termination Phase. This phase closes down this connection. This can happen if there is an authentication failure, if there are so many checksum errors that the two parties decide to tear down the link automatically, if the link suddenly fails, or if the user decides to hang up his connection.
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