How Names Should Be Formatted

Nov 24,2008 by alperen

Asking Someone Else to Look Up the Phone Number (IP Address) for You

How Names Should Be Formatted

For the DNS processes to work well, DNS defines some rules for how hosts are named. This section covers the structure and meaning of TCP/IP host names, plus some terminology related to name resolution.

First, the names must follow a format that helps the DNS servers decide which DNS should handle DNS requests for a particular name. You have probably noticed that the names used in this chapter, such as www.example.com and www.fredsco.com, have some sort of organization and structure. The last part of the name actually helps identify the DNS that can resolve the name.

TCP/IP hosts are organized into groups of hosts called domains. A domain consists of all hosts whose names end with the same text. For instance, the names www.example.com, ftp.example.com, and smtp.example.com would all be host names inside the example.com domain. The part in common among all the namesexample.com in this caseis called the domain name.

One or more DNS servers are considered to be the authoritative DNS server for a particular domain. That means that any names that end in that domain name should be resolved by that DNS server, and that DNS server has the ultimate authority for which names have which IP addressesat least for names in that domain. For instance, in Figure 13-4, the DNS server at address 150.1.3.4 was the authoritative DNS for domain example.com.

The structure of the DNS system works well. Inside a single company, the DNS administrator can change and add all the names he wants to. As long as the root DNS server knows the list of all the DNS servers and the domain names that they support, anyone on the Internet can ask for name resolution, have the request referred to the right DNS server, and learn the correct IP address.