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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

Previous Topic/Section
DNS Structural Elements and Terminology: Domains, Subdomains, and Nodes; Roots, Leaves and Branches; Parents, Children and Siblings
Previous Page
Pages in Current Topic/Section
12
3
Next Page
Absolute (Fully-Qualified) and Relative (Partially-Qualified) Domain Name Specifications
Next Topic/Section

DNS Labels, Names and Syntax Rules
(Page 3 of 3)

DNS Name Length Limit

There is a maximum limit of 255 characters for a complete domain name, for implementation purposes. In practice, most domain names are much shorter than this limit, as it would violate the whole purpose of domain names if we let them get so long that nobody could remember them anyway.

Resource Specification

In many protocols, it is possible to specify a particular resource within a domain name by providing a directory structure after a name. This is done using the standard TCP/IP uniform resource locator (URL) syntax, where a path is indicated using slashes to separate subdirectories. For example, a specific file at “salt.crystal.rocks” might be located at “salt.crystal.rocks/chem/composition”.

While DNS names are case-insensitive, the labels in a URL path are not. So this example would be different from “salt.crystal.rocks/chem/Composition”. See the topic on URL syntax for more details.

Key Concept: A domain name is a string of text that uniquely identifies a particular node in the name space. The domain name for a node is constructed by concatenating in right-to-left order all the labels in the branch of the DNS tree starting from the top of the tree down to the particular node, separating each by a dot (period.)



Previous Topic/Section
DNS Structural Elements and Terminology: Domains, Subdomains, and Nodes; Roots, Leaves and Branches; Parents, Children and Siblings
Previous Page
Pages in Current Topic/Section
12
3
Next Page
Absolute (Fully-Qualified) and Relative (Partially-Qualified) Domain Name Specifications
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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