Link Establishment Phase

The Link Control Protocol (LCP) is used to configure the PPP link during the link establishment phase. The configuration parameters are negotiated by an exchange of LCP frames. If the negotiation converges, the link is established and either the authentication protocol or network layer protocol phase is started. If the endpoints fail to negotiate a common configuration for the link, it is closed immediately.

During the link establishment phase only LCP frames should be transmitted in the PPP frames. All other frames are discarded.