PPP
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... simultaneous bi-directional operation, and are assumed to deliver
packets in order. It is intended that PPP provide a common solution
for easy connection of a wide variety of hosts ...
... network-layer protocols simultaneously over the same link. The
PPP encapsulation has been carefully designed to retain
compatibility ...
...
In order to be sufficiently versatile to be portable to a wide
variety of environments, PPP provides a Link Control Protocol
(LCP ...
...
It is intended that PPP links be easy to configure. By design,
the standard defaults handle all common configurations. The
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... PPP Encapsulation ...
...
A summary of the PPP encapsulation is shown below. The fields are
transmitted from left to right.
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... 0003 to 001f reserved (transparency inefficient)
007d reserved (Control Escape)
00cf reserved (PPP NLPID)
00ff reserved (compression inefficient)
...
... MRU), which defaults to 1500 octets. By
negotiation, consenting PPP implementations may use other values
for the MRU.
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... In order to establish communications over a point-to-point link, each
end of the PPP link MUST first send LCP packets to configure and test
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... In the process of configuring, maintaining and terminating the
point-to-point link, the PPP link goes through several distinct
phases which are specified in the following simplified state diagram ...
... After a NCP has reached the Opened state, PPP will carry the
corresponding network-layer protocol packets. Any supported
...
...
PPP can terminate the link at any time. This might happen because of
the loss of carrier, authentication failure ...
... link through an exchange of Terminate
packets. When the link is closing, PPP informs the network-layer
protocols so that they may take appropriate action.
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... the peer to disconnect, and MUST NOT disconnect until at least one
Restart time has passed after sending a Terminate-Ack. PPP SHOULD
proceed to the Link Dead phase.
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... the fact that one NCP has Closed is not sufficient reason to cause
the termination of the PPP link, even if that NCP was the only NCP ...
... Typically, this event is used by a modem handling or calling
process, or by some other coupling of the PPP link to the physical
media, to signal LCP ...
... Typically, this event is used by a modem handling or calling
process, or by some other coupling of the PPP link to the physical
media, to signal LCP ...
... 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 ...
... Exactly one LCP packet is encapsulated in the PPP Information field,
where the PPP Protocol field ...
... encapsulated in the PPP Information field,
where the PPP Protocol field indicates type hex c021 (Link Control
...
... Description
Reception of a PPP packet with an unknown Protocol field indicates
that the peer is attempting to use a protocol which is
...
...
The Rejected-Protocol field is two octets, and contains the PPP
Protocol field of the packet which is being rejected.
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... authentication protocol desired. Values for this field are always
the same as the PPP Protocol field values for that same
authentication protocol ...
... Protocol field is two octets, and indicates the link
quality monitoring protocol desired. Values for this field are
always the same as the PPP Protocol field values for that same
monitoring protocol.
...
... method to negotiate the
compression of the PPP Protocol field. By default, all
implementations MUST transmit packets with two octet PPP ...
... PPP Protocol field. By default, all
implementations MUST transmit packets with two octet PPP Protocol
fields.
...
... Protocol
fields.
PPP Protocol field numbers are chosen such that some values may be
compressed into a single octet form which is clearly
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... Compressed Protocol fields MUST NOT be transmitted unless this
Configuration Option has been negotiated. When negotiated, PPP
implementations MUST accept PPP packets with either double-octet
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... Configuration Option has been negotiated. When negotiated, PPP
implementations MUST accept PPP packets with either double-octet
or single-octet Protocol fields, and MUST NOT distinguish between
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