Link Control Protocol

LCP, described in RFC 1661, is a simple protocol to configure a common set of PPP connection parameters (for phase 1 of the PPP connection). It is also used by NCPs to configure specific data protocol configuration parameters (for phase 2 of the PPP connection). LCP uses the PPP Protocol ID 0xC0-21. Figure 4-1 shows an LCP frame.

The structure of an LCP frame

Figure 4-1. The structure of an LCP frame

The fields in the LCP frame are defined as follows:

  • Code. A 1-byte field that identifies the type of LCP message

  • Identifier. A 1-byte field that identifies a specific pair of LCP messages: the request and the response

  • Length. A 2-byte length field that indicates ...

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