PPP Configuration Options
PPP can be configured to support various functions including:
Authentication using either PAP or CHAP
Compression using either Stacker or Predictor
Multilink which combines two or more channels to increase the WAN bandwidth
These options are discussed in more detail in the next section.
To negotiate the use of these PPP options, the LCP link-establishment frames contain Option information in the Data field of the LCP frame. If a configuration option is not included in an LCP frame, the default value for that configuration option is assumed.
This phase is complete when a configuration acknowledgment frame has been sent and received.
NCP ProcessAfter the link has been initiated, the LCP passes control to the appropriate NCP. Although initially designed for IP datagrams, PPP can carry data from many types of network layer protocols by using a modular approach in its implementation. It can also carry two or more Layer 3 protocols simultaneously. Its modular model allows the LCP to set up the link and then hand the details of a network protocol to a specific NCP. Each network protocol has a corresponding NCP. Each NCP has a corresponding RFC. There are NCPs for IP, IPX, AppleTalk, and many others. NCPs use the same packet format as the LCPs.