Remote Access Authentication- PAP
Rarely used, Primarily because passwords are sent in clear text.
Remote Access Authentication- CHAP
Uses challenge response authentication process
Remote Access Authenticatio- MS-CHAP and MS-CHAPv2
Microsoft improvement over CHAP.
CHAPv2 provides mutual authentication
Remote Access Authenticatio- RADIUS
Provides central authentication for multiple remote access services.
RADIUS uses UDP and only Encrypts the password during the authentication process.
Remote Access Authentication-TACACS / XTACACS
Two legacy protocols that are rarely used anymore. TACACS is generic, defined by RFC 1492, and uses UDP port 49.
XTACACS is a Cisco systems proprietary improvement over TACACS
Remote Access Authentication- TACACS+
Used by some Cisco and UNIX remote access systems as an alernative to RADIUS.
TACACS+ uses TCP, encrypts the entire authentication process, and supports multiple challenge and responces.
TACACS+ uses TCP port 49.
Remote Access Authentication