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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 Registration, Public Administration, Zones and Authorities

DNS Name Space Administrative Hierarchy Partitioning: DNS Zones of Authority 1 2 DNS Name Servers and Name Resolution

We have now seen the hierarchical nature of the DNS name space, and the authority structure that administers it. Name registration begins with the generic and country code top-level domains (TLDs) within the root of the name hierarchy, proceeds to second-level domains within the TLDs, and then lower-level subdomains below those. As we progress down the name tree, we move from the most general, public authority (IANA/ICANN, which runs all of DNS), through the high-level TLD authorities, and eventually down to the level of individual organizations, corporations and individuals.

This “dividing line” between public authorities and private authorities occurs in many different places in the name structure. Wherever it does occur, below that line, responsibility for the domain becomes that of the organization that registered it. It can further subdivide the name space, granting parts of it to other organizations or even reselling it if they wish. Alternately, they may decide to use the name space to create a purely internal structure. I call this private name registration, in contrast to the public name registration we discussed earlier in this section.

For example, if a company called XYZ Industries registers “xyzindustries.com”, they become the owner of not just that domain name, but any subdomain structure or named items within it that they may choose to create. This is, of course, the beauty and power of authority delegation and the hierarchical structure. The company has an important decision that they must make however: they must choose whether they want to create names that are part of the global DNS name structure, or if they want to use names within the structure purely privately.

If a company wants names within its domain to be part of the global DNS name structure, it is required to perform the work necessary to properly set up and manage these names so they fit into the Domain Name System. The most common example, of course, is creating a public World Wide Web server. Most companies name such servers beginning with “www”, so XYZ Industries would probably wish to have the name “www.xyzindustries.com” for its WWW server address.

Obviously, they want and need anyone on the Internet to be able to locate this server. Thus, even though XYZ has private control of the “xyzindustries.com” domain, and thus owns the name “www.xyzindustries.com”, they must follow proper procedures for ensuring that DNS resource records are set up for their “www” subdomain so everyone on the Internet can find it. They may do this themselves, if they run their own DNS servers, or may have an ISP or other third party do it for them, as described in the previous topic.

DNS Name Space Administrative Hierarchy Partitioning: DNS Zones of Authority 1 2 DNS Name Servers and Name Resolution