4d316111_ing_Kerberos__Support____Cisco_Table_1_Kerberos_Terminology_Definition
[Term] authentication [Definition] 
A process by which a user or service identifies itself to another service. For example, a client can authenticate to a router or a router can authenticate to another router.
User Security Configuration Guide, Cisco IOS XE Release 3S - Configuring Kerberos [Support] - Cisco