Full Title or Meme
A collection of Authentication protocols are compared and contrasted.
Since Kerberos was released at MIT in 1999 as a means to allow Single Sign On by students and staff to the variety of systems available at the university, the combination of one user sign on to a variety of different services has been promoted as necessary in the variety of network services now available to users. There are two distinct cases and a wide range of intermediate cases that are addressed by authentication protocols:
Captive users and services
At MIT and at most corporations there is a pre-existing legal agreement that is signed by all users that applies to all services.
In such a closed system in makes sense to allow Single Log Out so that a user can close their connection and go home for the day.
Federated or Open systems of users and services
In such an open system it is not often helpful for a user to be signed out of all web sites when they chose to sign out of (say) the purchase of concert tickets.