3.4.4 Higher-Layer Triggered Events
The AP exchange is triggered by a higher-layer application protocol that requests security services for a connection or message exchange. The higher-layer application protocol MUST specify the name of the server to which it is attempting authentication and also MUST specify any of the parameters from section 3.4.1 that are required for Kerberos V5 [RFC4120] to perform the authentication.
Calling applications use the SSPI API family to establish the connection and specify the target. Optionally, certain higher-layer protocols, such as Simple and Protected Generic Security Service Application Program Interface Negotiation Mechanism (SPNEGO) [MS-SPNG], will also specify the parameters.