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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)
                     9  DNS Name Space, Architecture and Terminology

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DNS Domains and the DNS Hierarchical Name Architecture
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DNS Labels, Names and Syntax Rules
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DNS Structural Elements and Terminology: Domains, Subdomains, and Nodes; Roots, Leaves and Branches; Parents, Children and Siblings
(Page 1 of 3)

Now that we understand the fundamentals of the Domain Name System's name space, let's look at the DNS structure in more detail. At the same time, we can get a better handle on the many different terms used to refer to parts of the DNS domain name hierarchy.

DNS Tree-Related Terminology

We saw in the previous topic that the DNS name structure is shaped somewhat like a tree; the comparison between structured elements and trees is a common one in networking. The main difference between technology and biology here is that DNS trees grow from the top down, instead of reaching for the sky. The analogy to a tree naturally leads to the use of several tree-related terms in describing the DNS name structure, some of which are illustrated in Figure 236:

  • Root: This is the conceptual top of the DNS name structure. The root domain in DNS contains the entire structure. By definition, it has no name; it is null.

  • Branch: A branch is any contiguous portion of DNS hierarchy. It consists of a domain and all the domains and objects within it. All branches connect together to the root, just like in a real tree. (Yes, it would be better if the root were called the trunk, but computer science majors apparently don't take botany as electives. J)

  • Leaf: This is an “end object” in the structure, that is, a domain that doesn't have anything underneath it. Again, the analogy to a leaf being at the end of a sequence of branches is apt.

There is no specific term to refer to a domain that is not a leaf. These are sometimes called interior nodes, meaning that they are in the middle of the structure. A node is the generic computing term for an object in a topology or structure; it is used throughout this Guide. So, in DNS, every node is a domain, and may be either an interior node that contains additional domains and/or objects, or a leaf that is a specific named device. The term domain is thus somewhat ambiguous, as it can refer to either a collection of objects which represents a branch of the tree, or a specific leaf.


Previous Topic/Section
DNS Domains and the DNS Hierarchical Name Architecture
Previous Page
Pages in Current Topic/Section
1
23
Next Page
DNS Labels, Names and Syntax Rules
Next Topic/Section

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