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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  Name Systems and TCP/IP Name Registration and Name Resolution
           9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)
                9  TCP/IP Domain Name System (DNS)

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DNS Private Name Registration
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DNS Name Server Concepts and Operation
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DNS Name Servers and Name Resolution

The preceding two sections describe the Domain Name System's hierarchical name space, and the authorities that manage it and are responsible for name registration. These two elements, the name space and name registration, are the more “intangible” parts of the name system, which define how it is created and managed. The “tangible” aspect of the name system is the set of software and hardware that enables its primary “active function”: name resolution. This is the specific task that allows a name system to replace cumbersome numeric addresses with easy-to-use text names.

Name resolution is the part of DNS that generally gets the most attention, because it is the portion of the system that most people work with on a daily basis. DNS uses a very capable client/server name resolution method that makes use of a distributed database of name information. The most commonly used implementation of the DNS name resolution process is, of course, the one used for the Internet itself, which resolves many billions of name requests every day.

In this section I explain in detail the concepts and operation of the DNS name resolution function. The section is broken into three subsections. The first two cover each of the two key software elements that work together to implement the DNS client/server name resolution function. The first describes DNS name servers, and how they represent, manage and provide data when resolution is invoked. The second describes DNS clients, called resolvers, how they initiate resolution, and the steps involved in the resolution process. After these I have a third subsection that ties together the information about name servers and resolvers by providing a look at message exchange between these units, and describing the formats of messages, resource records and DNS master files.

Background Information: The material in this section assumes that you are already familiar with the topics in the preceding two sections, and references those sections where appropriate. If you have not already read the sections on the DNS name space and name registration, you should at least review the overview of DNS components and general functions.


Related Information: A set of related TCP/IP utilities called nslookup, host and dig can be used by an administrator to query DNS name servers for information. They are useful for a variety of purposes, including manually determining the IP address of a host, checking for specific resource records maintained for a DNS name, and verifying the name resolution function. See the topic discussing these programs in the section on TCP/IP administration utilities.


Quick navigation to subsections and regular topics in this section



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