Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Enjoy The TCP/IP Guide? Get the complete PDF!
The TCP/IP Guide

Custom Search







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

Previous Topic/Section
DNS Domains and the DNS Hierarchical Name Architecture
Previous Page
Pages in Current Topic/Section
1
2
3
Next Page
DNS Labels, Names and Syntax Rules
Next Topic/Section

DNS Structural Elements and Terminology: Domains, Subdomains, and Nodes; Roots, Leaves and Branches; Parents, Children and Siblings
(Page 2 of 3)

DNS Domain-Related Terminology

There are also several “domain-like” terms that are often used to refer to domains at different levels of the hierarchy. These terms, shown in Figure 236, include:

  • Root Domain: This is the root of the tree, as before.

  • Top-Level Domains (TLDs): These are the highest-level domains directly under the root of the tree. They are also sometimes called first-level domains.

  • Second-Level Domains: Shockingly enough, these are the domains located directly below the top-level domains.

  • Subdomains: In some contexts, this term refers only to domains that are located directly below the second-level domains (but see below).

    Figure 236: DNS Name Space Tree and Domain-Related Terminology

    The top of the DNS name space is the root of the tree, and has no name. Under the root comes any number of top-level domains (TLDs); within each of these can be placed second-level domains, then within those subdomains, and so forth.

    Some of the “tree” terminology used in DNS is also shown here. The portion of the tree with the purple background is one branch; the blue area highlights a smaller “sub-branch” within that branch. The green nodes within that blue area are the leaves of that smaller branch of the tree.

     


Key Concept: The top of the DNS name space is the root; under the root come top-level domains, and within these are second-level domains and then subdomains. In theory, any number of levels of subdomains can be created. A branch is any contiguous portion of the DNS tree; a leaf is a domain with nothing underneath it in the structure, and usually represents a single device.


The term “subdomain” can also be used generically, like the word “domain” itself. In that case, it refers simply to the relationship between two domains, with a subdomain being under another domain in the structure. This means, for example, that top-level domains can be said to be subdomains of the root; every second-level domain is a subdomain of a top-level domain, and so on. But again, sometimes “subdomain” means specifically a third-level or lower domain.


Previous Topic/Section
DNS Domains and the DNS Hierarchical Name Architecture
Previous Page
Pages in Current Topic/Section
1
2
3
Next Page
DNS Labels, Names and Syntax Rules
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.