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Another type of Namespace that we're going to become very familiar with as this course progresses is DNS Namespace. Just like the NetBIOS Namespace, the DNS Namespace really exists for the same purpose and that is to give names to computing devices. Or more specifically network cards. Now in the DNS world, in the DNS Namespace these network cards are known as hosts. Anything that binds an IP address to it is known as a host in the DNS Namespace. The thing that differs when you compare DNS to NetBIOS is that DNS is a hierarchical Namespace meaning that it is divided up into parent child domains. What this allows for is that names can be reused. Can we reuse the domain space of Bean Lake, yes as long as it's unique in the parent level domain space of org. Same thing with ftp1, can there be more servers then just one named ftp1, of course, there can thousands of them. The other thing about a DNS Namespace, we want to recognize right of the bat is that in this parent-child domain space we build names or we generate names for computing devices by giving them fully qualified domain names. And a fully domain name identifies the host name plus it identifies any parent domains in which that host lives. I mentioned earlier at the beginning of this that the purpose is the same and that is, so that we can resolve a name that we can use names when computers are trying to talk but the computers need numbers. So we resolve these names to IP addresses by using either a host file or a DNS server. The host file is the DNS equivalent of the LMHost file, the DNS server is the NetBIOS equivalent of the WIN server. This is a static text file, this can be a dynamic database of names to IP addresses. Again we'll spend a whole chapter talking about DNS server later on. To show you a little bit more of what we're talking about here, this is from the help files of Server 2003 and this helps visualize the domain space or the hierarchy of the DNS Namespace. And what's significant here what this graphic helps us see is that all of the DNS Namespace starts with a root level domain, and that's why if you go back to that fully qualified domain name, I had the root domain in parenthesis. You no longer have to specify that root domain when you use fully qualified domain names but that wasn't always the case. Underneath the root level domain there's the com level domains, these are top-level domains com, edu, gov, int, mil etc, etc. And then underneath these top-level domains are second level domains and these are the ones that we control. We don't control these, these are controlled by the Internic, these are controlled when we register, when we check with the Internic to see if the domain is unique, we can then control the hosts that are in these domains or we can create sub-domains like, for example, the examples of domain. So here's a picture because we cant really touch domains. Where's the Microsoft domain? Well, who knows, we might be able to say where a Microsoft web server is or a Microsoft DNS server is. We can put our hands on those things. But as far as the Microsoft domain, you can't, it's a logical entity. Another way to look up your computer's fully qualified domain name is to look at the properties, the system properties dialog box, which you can access by right clicking on my computer, choosing properties and then once the system properties dialog box pops-up, click on computer name and there is the full computer name. Now notice this is going to change, right now there is no domain space because I'm in a workgroup, but another thing you can do if you want to, you can do this from the system properties dialog box, you can also access your host name from a command prompt with the command host name. It returns to you your host name. Just a couple of considerations here, we're again laying the groundwork of understanding. We spend a whole other chapter talking about DNS. but we want to get a better understanding of what the DNS Namespace is before we go on and configure DNS servers.