I was asked this question in an interview, and I have no idea what the answer is.
I know we have Windows authentication mode and SQL Server authentication. But the interviewer said that we have two protocols that Windows verify when using Windows authentication.
I just can't find anything on the Internet about this.
Best Answer
They were probably looking for an answer that discuss the "Kerberos" and "NTLM" Windows authentication protocol/schemes.
Once you know what to search for, there are lots of articles online about how these schemes relate to SQL Server:
Understanding Kerberos and NTLM authentication in SQL Server Connections
...and
Comment: emphasis/meaning added
How to make sure that you are using Kerberos authentication when you create a remote connection to an instance of SQL Server 2005