For people to be able to reach your site on an intranet or the Internet, you must have a unique IP address that identifies your computer on the network. This address takes the form of a long string of numbers separated by dots. Because the numeric address is difficult for people to remember, text names are used by sites to provide visitors with an easy-to-remember address. The text name must be resolved by a naming system to the correct numerical address. To select the name resolution system best suited to your situation, this section describes how different systems resolve text names to numerical addresses.
An intranet is a private local area network (LAN) that uses Internet technology. To receive and deliver information packets successfully, each computer on the intranet must have a unique address. In addition, each computer also has a text name. The names and addresses can be assigned by using any of several different name-to-address resolution systems. The system you select is based on the size of your intranet, how often computers are added or moved, and the software installed on Windows NT Server. The following sections describe various ways computers on intranets receive their names and addresses.
IP addresses can be assigned in the following two ways. Your network can use just one, or a mixture of both:
Windows NT networking components rely on a naming convention known as NetBIOS. In contrast, TCP/IP components rely on a naming convention known as the Domain Name System (DNS). Under Windows NT, the DNS host name defaults to the same name as the NetBIOS computer name. As with the assignment of IP addresses, the mapping of computer names to IP addresses can be done in multiple ways:
DNS names are typically resolved using static information. The DNS server contains a portion of the static database listing host names and addresses. If the requested name is not in the DNS server's portion of the database, it sends a query to other DNS servers to get the requested information. The DNS server that runs on Windows NT can be configured to query a WINS server for name resolution of the lower levels of the DNS hierarchical naming structure. Because WINS assigns computer names dynamically, this effectively changes DNS from a static system to a dynamic system.
If you want to assign multiple names to one computer, you must use a static name assignment for the computer. You can map multiple names to one IP address on one computer, or multiple names, each with its own IP address, to one computer. For more conceptual information about naming sites, see Assigning Names, Addresses, and Ports to Web Sites later in this section. For procedural help naming sites, see Naming Web Sites.
On the Internet, the Domain Name System (DNS) is used to resolve text names to IP addresses for sites. This section describes how Internet sites get their names.
The DNS names are recorded by InterNIC, an organization that manages name and address assignment on the Internet. InterNIC operates a distributed database that contains all the registered domain names. When a client computer requests a connection to a site using a domain name, the request is transmitted to a series of computers called the Domain Name Servers.
The Domain Name Servers are located in thousands of companies around the world. They communicate in DNS, a remarkably fast and compact language. The Domain Name Servers return the IP address that corresponds to the requested domain name, and then the client request is routed to the appropriate site. Getting an Internet Name and Address contains information on registering a domain name for your site.
This section explains assigning identification information to Web sites. Each Web site has a unique, three-part identity it uses to receive and to respond to requests:
If you have one Web site and one FTP site, by default, they respond to the NetBIOS or DNS name for the computer, and the IP address assigned to the network card installed in the computer. The default Web port is port 80, and the default FTP port is port 21. (When your site uses these default port numbers, visitors do not have to append a port number to your address in order to reach your site.)
Suppose your department is renamed as the result of a reorganization, or your company is renamed as the result of a merger. Because ”friendly” text names for Web sites usually bear a resemblance to the department or company that hosts them, you may want to change the name associated with the address of your site. You can configure your Web site to respond to both the previous name and the new name, provided your network correctly routes both requests to your computer. This way, visitors can still reach you using the old name, while becoming familiar with the new name.
If you have a high-volume site, you might have multiple network cards installed in your computer, each with its own IP address. By default, a Web site responds to all IP addresses not assigned to another Web site. You can create additional Web sites that share a name and port number, but respond to different addresses. Each Web site you create can be assigned one or more IP addresses.
If you are migrating from a previous Web server that used a port other than port 80, you can assign both port 80 and the previous port number to one domain name, ensuring that visitors still reach your site. Keep in mind that if you assign port numbers other than the standard port numbers, visitors must append the port number to addresses they type in their browsers.
When you create additional Web sites, you must ensure that each Web site has a unique identity. Web sites can share any two of their three identity parts with other Web sites, provided the sites are differentiated on the third part. This means that two sites can share their host header name and IP address, but must use different ports. Alternately, they could share a host header name and port, but have different IP addresses.
One of the most useful and interesting scenarios is sharing IP addresses and ports, but having different host header names. Using this strategy, you can operate multiple domain names on one IP address. Be aware that older browsers are not able to pass names they are requesting in the header. Visitors using older browsers reach the default Web site for the IP address and require additional support to reach the correct site. Newer browsers pass the name requested in their header. IIS routes these visitors to the correct Web site. For instructions on how to assign names, see Naming Web Sites. For instructions on enabling host header support for older browsers, see Supporting Host Header Names in Older Browsers.