DNS domain tree

DNS domain tree

 DNS has conventions for naming. If you are only operating in a local network, you can assign a name arbitrarily, but in a network that targets the Internet, you must make sure that domain names do not overlap, and everyone understands. It should be a name that is easy to remember.

Therefore, the DNS naming convention is as shown in the figure below.

 DNS names are expressed in a hierarchical structure called a domain tree. It is divided into several hierarchies by ".", each hierarchy has a meaning as a group, and it has a decentralized structure that manages lower domains and host names. The load is distributed by using a distributed structure.

 The branched and hierarchical parts are called "domains" and are also called "nodes". From top to bottom they are called first-level domains, second-level domains, and so on.

 Each node manages the IP address of the DNS server that has the information within the domain it manages and the information of its lower domain (subdomain).

 Each node only knows the information within the domain it manages and the information of the DNS servers of the lower domains, so when a client makes an inquiry to DNS, it is necessary to follow the hierarchy in order from the top.

Domain name type

Domain names in use today can be broadly classified into the following two categories when classified by top-level domain (TLD).

  • Technical top-level domain (gTLD: generic TLD)
  • country code top-level domain (ccTLD)

In addition to the above, there are TLDs for Internet infrastructure (Infrastructure TLDs), which cannot be registered by users.

● gTLDs

comfor commercial organizations
netfor networks
orgfor non-profit organizations
edufor educational institutions
governmentFor U.S. government agencies
milUS military
intfor international organizations
infoNo limit
bizbusiness user


hkHong Kong
krSouth Korea
ruRussian Federation
usunited states of america
zaRepublic of South Africa

Organization names and host names are specified in the hierarchy below the TLD.

●Organization name

You can add this part arbitrarily, but you cannot use what already exists (including higher TLDs).

●Host name

 This part can also be attached arbitrarily, but it does not mean that anything is acceptable. A common naming convention exists to avoid confusion. Servers are usually published using names given by this naming scheme.

wwwWeb server
pop, pop3, smtpmail server
dnsDNS server
FTPFTP server