Authentication & authorization
CHAP: also allows server-controlled “re-authentication”
Kerberos: single sign-on to multiple servers
Alt: digital signatures (discussed later): authenticates every message.
Authorization:
- Which resources can this user access ?
- Achieved using “access control lists” (ACLs) stored in database or directory
Client-server rather than peer-peer for better manageability (eg: RADIUS vs CHAP/PAP)