Authentication validates a user's claim to a specific identity within a security system.
This may be a simple password scheme, or it may involve robust digital signatures and multiple-factor systems from token cards to biological systems. Once authenticated, authorization constrains the actions that a user can take within the network. Once traditional packet filters are linked to user state through a central directory, for example, the network can limit the range of locations that the user can visit on the network. Often, however, authorization systems involve access to specific applications and services such as printer queues or file servers. Simply constraining users does not make a secure network.