The requirement for authentication in a connection is indicated by including the optional authentication parameter in the features parameter for the GET /info method.
Tableau currently supports basic authentication with username and password.
The username and password values that have been configured in Tableau are passed to the Analytics Extension using the HTTP headers of calls to the /evaluate and /query/{function_name} methods.
If the authentication requirement is turned off in the Analytics Extension but a username and password are still included in the request, the Analytics Extension will respond with a 406 error.
On the Tableau side, Authentication is configured in Tableau Desktop via the Analytics Extensions UI: https://help.tableau.com/current/pro/desktop/en-us/r_connection_manage.htm#configure-an-external-service-connection
In Server up to version 2020.1, connections with are configured for Analytics Extensions using the TSM Security command: https://help.tableau.com/current/server/en-us/cli_security_tsm.htm#tsm_security_vizql-extsvc-ssl-enable
For information about how to configure SSL on Tableau Server, see Server SSL.