EAP 
Extensible Authentication Protocol 
When you log on to the Internet, you're most likely establishing a PPP connection via a remote access server. The password, key, or other device you use to prove that you are authorized to do so is controlled via PPP's Link Control Protocol (LCP). LCP is somewhat inflexible, however, because it has to specify an authentication device early in the process. EAP lets the system gather more information from the user before deciding which authenticator to use; it's called extensible because it allows more authenticator types than LCP did, such as passwords, public keys, or biometrics.