The various versions of Windows have used Kerberos as its main authentication protocol for over 20 years. However, in certain circumstances, the OS has to use another method, NTLM (NT LAN Manager).
Server: Fully-patched 2008 R2, running Certificate Services. The /certsrv virtual directory is using (I believe) default settings. Specifically, this means it's using Windows Authentication, with NTLM ...