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DNS Overview_IIS_SP1_TechRef

Updated: August 22, 2005

Applies To: Windows Server 2003 with SP1

The Internet employs Transmission Control Protocol/Internet Protocol (TCP/IP) to locate and connect to network hosts, which are computers or other network devices. Each network host is identified by a unique IP address. For users to reach your IIS-based Internet site or service, you must have a unique IP address.

IP addresses are expressed in dotted-decimal notation and segmented into four 8-bit octets, for example, It is difficult to remember and use numeric IP addresses, and many people prefer to use alphanumeric names. To address this issue, Domain Name System (DNS) provides a standard naming convention for locating IP-based computers. When you use DNS, clients can connect to an Internet site or service by typing a DNS domain name (such as in their browsers, rather than an IP address (such as A DNS domain name such as is easier to remember and type correctly.

The process of mapping a DNS domain name to an IP address is called name resolution. DNS name resolution is performed by a DNS service, such as the DNS service provided with the Microsoft® Windows® Server 2003, Standard Edition; Windows® Server 2003, Enterprise Edition; and Windows® Server 2003, Datacenter Edition, operating systems. For more information about Windows Server 2003 DNS, see DNS in Help and Support Center for Windows Server 2003.

Before you can set up an IIS-based Internet site or service, you must obtain an IP address, and if you want users to be able to use a DNS domain name to connect to your Internet site or service, you must also register a unique DNS domain name. Before you request a DNS domain name to register, decide on a plan for your DNS namespace.

Namespace Planning for DNS

DNS uses a namespace that is hierarchically structured and based on the concept of a tree of named domains. The tree has multiple levels:

  • The root domain. The root domain is the top-level organizational domain. Root domain names include com, org, and gov.

  • Second-level domains. Second-level domains provide an identifying name. For example, if your company is named Contoso Pharmaceuticals, then the second-level domain can be contoso in

  • Subdomains. Subdomains are arranged according to departments, geography, or other logical divisions to help users find information as quickly as possible. For example, you can create a subdomain of

The DNS namespace includes globally unique identifiers — Internet domain names, IP address numbers, protocol parameter and port numbers, and others — that are assigned to the organizations that request them. These identifiers must be unique for the Internet to function.

To effectively plan your DNS namespace, consider the long-term organization of your network architecture, as well as how users might look for information. For more information about namespace planning, see Namespace planning for DNS in Help and Support Center for Windows Server 2003.

Registering a DNS Domain Name

Your Internet service provider (ISP) should assign you an IP address for your server that you will use when you configure IIS to host your Internet site or sites. To register a DNS domain name, you can work directly with a naming authority. Many ISPs can register a DNS domain name for you. The InterNIC Web site maintains a list of registrars that are currently taking registrations for all available top-level domains. The InterNIC Web site organizes and lists these registrars alphabetically, by name, by location, and by supported languages. After you register your DNS domain name, your ISP or registrar can host the domain, or you can host the domain yourself (if you are a more advanced user). For more information about domain name registration services, see the InterNIC Web site.

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