LCP
allows an optional link-quality determination phase following the link
establishment and configuration negotiation phase. In the link-quality
determination phase, the link is tested to determine whether the link
quality is good enough to bring up network-layer protocols.
In addition, after the link has been
established and the authentication protocol chosen, the client or
user workstation can be authenticated. Authentication, if used, takes
place before the network-layer protocol configuration phase begins.
LCP can delay transmission of network-layer protocol information until
this phase is completed.
PPP supports two authentication
protocols: Password Authentication Protocol (PAP) and Challenge
Handshake Authentication Protocol (CHAP). Both of these protocols are detailed in RFC
1334, "PPP Authentication Protocols." These protocols are
covered later in this chapter, in the section "PPP
Authentication."
|