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doc-exports/docs/dns/umn/dns_pd_0009.html
Qin Ying, Fan 9a9e02c671 DNS UMN 20240223 version 
Reviewed-by: Hajba, László Antal <laszlo-antal.hajba@t-systems.com>
Co-authored-by: Qin Ying, Fan <fanqinying@huawei.com>
Co-committed-by: Qin Ying, Fan <fanqinying@huawei.com>
2024-06-07 13:20:48 +00:00

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Domain Name Format and DNS Hierarchy

A valid domain name meets the following requirements:

  • A domain name is segmented using dots (.) into multiple labels.
  • A domain name label can contain letters, digits, and hyphens (-) and cannot start or end with a hyphen.
  • A label cannot exceed 63 characters.
  • The total length of a domain name, including the dot at the end, cannot exceed 254 characters.

A domain name is divided into the following levels based on its structure:

  • Root domain: . (a dot)
  • Top-level domain: for example, .com, .net, .org, and .cn
  • Second-level domain: subdomains of the top-level domain names, such as example.com, example.net, and example.org
  • Third-level domain: subdomains of the second-level domain names, such as abc.example.com, abc.example.net, and abc.example.org
  • The next-level domain names are similarly expanded by adding prefixes to the previous-level domain names, such as def.abc.example.com, def.abc.example.net, and def.abc.example.org.
Parent topic: Product Concepts