Most organizations use Windows Authentication (also called Integrated Authentication.) This method is the most common because it controls authentication and access through the same ways as other network resources.
The client's current credentials will be passed to the server and will be used when connecting to the data source. If the database server is on a different server, then they'll only receive the credentials if Kerberos Delegation has been configured. Kerberos will need to be set up and configured by a domain administrator. Most large organizations will have an existing process for doing this - the previous article contains all the information required.
Note: If the data source needs more information, you will have to enter it separately when the report is opened. This can be the case when, for example, the data source uses Basic authentication.
