The Point-to-Point Protocol (PPP)
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Auteur(s) : W. Simpson
Classé sous : Serial
RFC 1548 The Point-to-Point Protocol December 1993
When the lower layer becomes available (Up), a Configure-Request
In the Closed state, the link is available (Up), but no Open has
occurred. The Restart timer is not running in the Closed state.
Upon reception of Configure-Request packets, a Terminate-Ack is
sent. Terminate-Acks are silently discarded to avoid creating a
The Stopped state is the Open counterpart to the Closed state. It
is entered when the automaton is waiting for a Down event after
the This-Layer-Finished action, or after sending a Terminate-Ack.
The Restart timer is not running in the Stopped state.
Upon reception of Configure-Request packets, an appropriate
response is sent. Upon reception of other packets, a Terminate-
Ack is sent. Terminate-Acks are silently discarded to avoid
creating a loop.
The Stopped state is a junction state for link termination, link
configuration failure, and other automaton failure modes. These
potentially separate states have been combined.
There is a race condition between the Down event response (from
the This-Layer-Finished action) and the Receive-Configure- Request
event. When a Configure-Request arrives before the Down event,
the Down event will supercede by returning the automaton to the
Starting state. This prevents attack by repetition.
After the peer fails to respond to Configure-Requests, an
implementation MAY wait passively for the peer to send Configure-
Requests. In this case, the This-Layer-Finished action is not
used for the TO- event in states Req-Sent, Ack- Rcvd and Ack-Sent.
This option is useful for dedicated circuits, or circuits which
have no status signals available, but SHOULD NOT be used for
Simpson [Page 17]