Microsoft Networking Terms and Roles

The following are some networking terms and roles. You will be familiar with some of these terms, but it's always good to get a refresher.

Server A server is a machine that users connect to so that they can access resources located on that machine. These resources can be files, printers, applications, and so forth. Usually the type of server is dependent on the resource that the user needs. For example, a print server is a server that controls printers. A file server is a server that contains files. Application servers can run applications for the users. Sometimes you will hear a server referred to by the specific application that it may be running, such as "That's our SQL server" or "That's our Exchange server."

Domain Controller This server contains a replica of Active Directory. Active Directory is your database that contains all the objects in your network. A domain controller is a server that contains this database. Years ago (when we were using NT 3.51 and NT 4.0), we had to have a Primary Domain Controller (PDC) as well as Backup Domain Controllers (BDC), but that's not true today. All domain controllers are equal in a Windows Server 2008 network. Some domain controllers may contain extra roles, but they all have the same copy of Active Directory.

Member Server A member server is a server that is a member of a domain-based network, but it does not contain a copy of Active Directory. For example, it is recommended that Exchange be loaded on a member server instead of a domain controller. Both domain controllers and member servers can act as file, print, or application servers. It just depends on whether or not you need that server to have a replica of Active Directory.

Stand Alone Server A stand alone server is a server that is not a member of a domain. Many organizations might use this type of server for virtualization. For example, you load Windows Server 2008 with Microsoft's version of virtualization (Hyper-V) on a stand alone server. You can then create virtual machines that act as domain controllers to run the network.

Client Machine A client machine is a computer that normally is used for your end users in a company. The most common operating systems for a client machine are Windows XP, Windows Vista, and Windows 7.

DNS Server The Domain Name Service (DNS) server is a server that has the DNS service running on it. DNS is a name resolution service. DNS turns a host name into a TCP/IP address (forward lookup). DNS also has the ability to turn a TCP/IP address into a name (reverse lookup). When you install an operating system onto a computer, you assign that computer a hostname. The problem is that computers talk to each other using the TCP/IP protocol (example: 192.168.1.100). It would be difficult for most users to remember all the different TCP/IP addresses on a network. So normally you connect to a machine by using its hostname. DNS does the conversion of hostname to TCP/IP address for you.
The easiest way to understand how this works is to think of your phone number. If someone wants to call you and they don't have your telephone number, they call information. They give information your name and they get your phone number. Well, this is how a network works. DNS is information on your network. You give DNS a hostname and it returns a network telephone number (TCP/IP address). DNS is a requirement if you want to install Active Directory. You can install DNS before or during the Active Directory installation.

DHCP Server A Dynamic Host Configuration Protocol (DHCP) server is the server that runs the DHCP service. DHCP is the server on the network that assigns TCP/IP information to your computers dynamically. Every computer needs three settings to operate properly (with the Internet and intranet): a TCP/IP number, a subnet mask, and a default gateway (router number). Your computers can get this minimum information two ways: manually (someone assigns the TCP/IP information) or dynamically (automatically installed). DHCP can assign more than just these three settings. DHCP can assign any TCP/IP configuration information (DNS server,WINS server, time servers, etc.).
In the previous section on DNS, we said that DNS was information on your network. Well, following this example, DHCP would be the phone company. DHCP is the component that assigns the telephone number (TCP/IP address).

Global Catalog The Global Catalog is a database of all Active Directory objects without all the attributes. The Global Catalog is a partial representation of the Active Directory objects. Think of the Global Catalog as an index. This is what the Global Catalog does on your Active Directory domain. When you need to find a resource in the domain (user, published printer, and so forth), you can search the Global Catalog to find its location.
Domain controllers need to use a Global Catalog to help with user authentication. Global Catalogs are a requirement on an Active Directory domain. All domain controllers can be Global Catalogs, but this is not always a good practice. Your network should have at least two Global Catalogs for redundancy, but too many can cause too much Global Catalog replication traffic.

In the next section, we'll discuss the Windows Server 2008 operating system.