For Windows Server 2016, is it correct recognition that the protocol used is Kerberos 5, when using Active Directory's sign in?
Yes, it is.
The Windows Server operating systems implement the Kerberos version 5 authentication protocol and extensions for public key authentication, transporting authorization data, and delegation. https://learn.microsoft.com/en-us/windows-server/security/kerberos/kerberos-authentication-overview
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