I'm using Windows Server 2008 R2. I just stopped IIS and tried using FTP—it worked! So, is FTP independent from IIS? How does it work if IIS is stopped?
In logical terms the FTP service is part of IIS which is a collection of services hence the name 'Internet Information Services'.
In Windows Server the role is called 'Web Server (IIS)' which is a bit misleading because you can run the ftp service without installing any http related services.
The FTP service runs as its own Windows Service process 'Microsoft FTP Service' (svchost.exe -k ftpsvc)