Section 4.1. Nuts and Bolts


4.1. Nuts and Bolts

Let's go through the basic building blocks of DNS first before we break into more advanced concepts. I'm going to provide you with a very fundamental, introductory look at DNS, and then in the following sections I'll break down each part with more detailed explanations and examples. Think of this as an abstract or executive summary, just so we're all on the same page before I move on to more technical topics.

The main premise of DNS is to provide name resolution servicesthat is, to resolve friendly textual hostnames to their associated IP addresses. DNS is the de facto standard for name resolution on the Internet and in modern networks that use TCP/IP as the transmission protocol. DNS is based on domains, which are simply textual names that refer to computers. There are top-level domains (TLDs), including some that are probably familiar to you: .COM, .NET, .ORG, and the like. There are also second-level domains, which are less inclusive and usually take the form of name.tld. For example, my domain is jonathanhassell.com. O'Reilly has a domain name of oreilly.com. CNN's domain is cnn.com.

Politically, there is an organization called ICANN, short for the Internet Consortium of Assigned Names and Numbers, which keeps track of all the top-level domains. This keeps utter confusion from breaking out when thousands upon thousands of top-level domains might be issued. Individuals and businesses are allowed to register second-level domain names beneath top-level domainshasseltech.net, for example.

DNS resolves names based on zones. Zones contain information on computers, services, and IP addresses for a collection of computers. Zones typically correspond to DNS domains, but they certainly do not have to. The DNS server or servers in a zone that contain a readable and writeable copy of the zone file (which contains all that information on computers, services, and addresses) is considered to be authoritative. You must have at least one authoritative server per zone for DNS to function. Any other DNS servers within this zone are considered to be secondary servers, meaning they hold only a readable copy of the DNS zone file.

Finally, there are two types of zones: forward lookup zones, which resolve hostnames to IP addresses, and reverse lookup zones, which do the opposite and resolve IP addresses to hostnames. Reverse lookup zones fall under a special top-level domain named in-addr.arpa, which ordinary users and clients never see in the course of their mainstream work.

Now, let's take a closer look at these elements of DNS.



    Learning Windows Server 2003
    Learning Windows Server 2003
    ISBN: 0596101236
    EAN: 2147483647
    Year: 2003
    Pages: 149

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