What is a domain controller?

If we are going to discuss the core infrastructure services that you need to piece together your Microsoft-driven network, there is no better place to start than with the domain controller. A Domain Controller, commonly referred to as a DC, is simply a server that is hosting Active Directory. It is a central point of contact, a central "hub" so to speak, that is accessed prior to almost any communication that takes place between a client and server in your network. Perhaps the easiest way to describe it is as a storage container for all identification that happens on the network. Usernames, passwords, computer accounts, groups of computers, servers, groups and collections of servers, security policies, file replication services, and many more things are stored within and managed by DCs. If you are not planning to have a domain controller be one of the first servers in your Microsoft-centric network, you might as well not even start building that...