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RFC1661 - часть 21

value, and to suggest a new, acceptable value. Configure-Reject

packets are used to refuse all negotiation about a Configuration

Option, typically because it is not recognized or implemented.

The use of Configure-Nak versus Configure-Reject is more fully

described in the chapter on LCP Packet Formats.

Send-Terminate-Request (str)

A Terminate-Request packet is transmitted. This indicates the

desire to close a connection. The Restart timer is started when

the Terminate-Request packet is transmitted, to guard against

packet loss. The Restart counter is decremented each time a

Terminate-Request is sent.

Send-Terminate-Ack (sta)

A Terminate-Ack packet is transmitted. This acknowledges the

reception of a Terminate-Request packet or otherwise serves to

synchronize the automatons.

Send-Code-Reject (scj)

A Code-Reject packet is transmitted. This indicates the reception

of an unknown type of packet.

Send-Echo-Reply (ser)

An Echo-Reply packet is transmitted. This acknowledges the

reception of an Echo-Request packet.

4.5. Loop Avoidance

The protocol makes a reasonable attempt at avoiding Configuration

Option negotiation loops. However, the protocol does NOT guarantee

that loops will not happen. As with any negotiation, it is possible

to configure two PPP implementations with conflicting policies that

will never converge. It is also possible to configure policies which

do converge, but which take significant time to do so. Implementors

should keep this in mind and SHOULD implement loop detection

mechanisms or higher level timeouts.

Simpson [Page 23]

RFC 1661 Point-to-Point Protocol July 1994

4.6. Counters and Timers

Restart Timer

There is one special timer used by the automaton. The Restart

timer is used to time transmissions of Configure-Request and

Terminate-Request packets. Expiration of the Restart timer causes

a Timeout event, and retransmission of the corresponding

Configure-Request or Terminate-Request packet. The Restart timer

MUST be configurable, but SHOULD default to three (3) seconds.

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