| Value | Description |
| RPC_C_AUTHN_LEVEL _NONE | Performs no authentication. |
| RPC_C_AUTHN_LEVEL _CONNECT | Authenticates only when the client establishes a relationship with the server. Datagram transports always use RPC_AUTHN_LEVEL_PKT instead. |
| RPC_C_AUTHN_LEVEL _CALL | Authenticates only at the beginning of each remote procedure call when the server receives the request. Datagram transports use RPC_C_AUTHN_LEVEL_PKT instead. |
| RPC_C_AUTHN_LEVEL _PKT | Authenticates that all data received is from the expected client. |
| RPC_C_AUTHN_LEVEL _PKT_INTEGRITY | Authenticates and verifies that none of the data transferred between client and server has been modified. |
| RPC_C_AUTHN_LEVEL _PKT_PRIVACY | Authenticates all previous levels and encrypts the argument value of each remote procedure call. |