Chapter
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6-9
protocol packets, and link quality monitoring packets can be switched, while
other types of packets are all discarded without being processed.
4. Network
stage
After PPP completes the previous stages, it enters this stage. In this case, the
corresponding NCP is required to configure the corresponding network protocol.
For example, IPCP is used to configure IP (Internet Protocol), and IPXCP is
used to configure the IPX protocol. Once the NCP reaches the Opened state, PPP
can transmit packets of this network protocol. This stage lasts until an event
notifies to terminate or close the link.
5. Terminate
stage
PPP may terminate a link at any time, for example, bottom-layer link failure,
authentication failure, link quality failure, and link closing initiated by the
management layer. At this stage, the PPP switching LCP Terminate packet closes
the link.
6.2.3.2 Running Process of PPP
Running process of PPP:
1. Before establishing a link, PPP implements LCP negotiation, whose content
includes the maximum transmission unit, whether authentication is needed, and
authentication protocols needed (PAP or CHAP) (For the installation of an
embedded BAS, authentication of user identity is always necessary).
2. PPP enters the "Establish" stage after LCP negotiation. At this time, the LCP
state is "Opened" indicating that a link has been established.
3. If authentication (remote end authenticates local end or local end authenticates
remote end) is enabled in the configuration, PPP enters the "Authenticate" stage
to start CHAP or PAP authentication.
4. In case of authentication failure, PPP enters the "Terminate" stage to remove the
link. And the LCP state turns to "Down". If authentication succeeds, PPP enters
the "Network" stage (NCP). At this time, the LCP state is still "Opened" while
the IPCP state and IPXCP state turn from "Initial" to "Request"
5. NCP negotiation modes supports IPCP negotiation and IPXCP negotiation. IPCP
negotiation mainly includes both parties’ IP addresses while IPXCP negotiation