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RFC1661 - часть 13


no Open has occurred. The Restart timer is not running in the

Initial state.

Starting

The Starting state is the Open counterpart to the Initial state.

An administrative Open has been initiated, but the lower layer is

still unavailable (Down). The Restart timer is not running in the

Starting state.

When the lower layer becomes available (Up), a Configure-Request

is sent.

Closed

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

loop.

Stopped

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.

Rationale:

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

Simpson [Page 14]

RFC 1661 Point-to-Point Protocol July 1994

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.

Implementation Option:

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




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