Extensible Authentication Protocol (EAP)

EAP stands for Extendible Authentication Protocol and it is used for the PPP authentication. It supports multiple authentication mechanisms such as certifications, token cards, smart cards and public key encryption. It provides an infrastructure for the network access.

Microsoft Windows uses EAP to authentication point to point based communications such as dial up, VPN, site to site connections and other types of computer to network connections. 

EAP was developed by Microsoft, Cisco and RSA security.  EAP provides an authentication framework and there are different methods in this framework. The main methods include EAP-MD5, EAP-OTP, EAP-GTC, EAP-TLS, EAP-IKEv2, EAP-SIM, and EAP-AKA