When PPP connections are started, the links go through three phases of session establishment,
as shown in Figure 1
FIGURE 1 PPP session establishment
Link-establishment phase LCP packets are sent by each PPP device to configure and test the
link. These packets contain a field called the Configuration Option that allows each device to
see the size of the data, compression, and authentication. If no Configuration Option field is
present, then the default configurations will be used.
Authentication phase If required, either CHAP or PAP can be used to authenticate a link.
Authentication takes place before Network layer protocol information is read. And it’s possible
that link-quality determination will occur simultaneously.
Network layer protocol phase PPP uses the Network Control Protocol (NCP) to allow multiple
Network layer protocols to be encapsulated and sent over a PPP data link. Each Network layer
protocol (e.g., IP, IPX, AppleTalk, which are routed protocols) establishes a service with NCP.
as shown in Figure 1
FIGURE 1 PPP session establishment
Link-establishment phase LCP packets are sent by each PPP device to configure and test the
link. These packets contain a field called the Configuration Option that allows each device to
see the size of the data, compression, and authentication. If no Configuration Option field is
present, then the default configurations will be used.
Authentication phase If required, either CHAP or PAP can be used to authenticate a link.
Authentication takes place before Network layer protocol information is read. And it’s possible
that link-quality determination will occur simultaneously.
Network layer protocol phase PPP uses the Network Control Protocol (NCP) to allow multiple
Network layer protocols to be encapsulated and sent over a PPP data link. Each Network layer
protocol (e.g., IP, IPX, AppleTalk, which are routed protocols) establishes a service with NCP.
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