Domain Controller
At least one computer in such a domain act as a domain controller (DC).
The domain controller keeps a list of all memebers of the domain.
Optionally, the domain controller also provides an Active Directory service.
The Domain Controller is able to
authenticate its members which is essential to build trust among the domain's members.
The Domain Controller has an identifier that is known to all its members.
dcpromo.exe
dcpromo.exe
is a utility to create a new Windows domain.
It reuses the computer's
SID to for the new Domain SID.
If the domain is demoted, a new SID is generated for the computer.