The DNS Name Space

The DNS name space is the set of all domain names that are registered in the DNS. These domain names are organized into a tree-like structure, with the top of the tree being the root domain. Below the root domain, there are a number of top-level domains, such as .com, .net, and .org. Below the top-level domains, there are second-level domains, and so on. Each domain name in the DNS name space corresponds to a set of resource records, which contain information about that domain name, such as its IP address, mail servers, and other information.

The DNS name space is hierarchical, meaning that each domain name can have subdomains beneath it. For example, the domain name "example.com" could have subdomains such as "www.example.com" and "mail.example.com". This allows for a very flexible and scalable naming structure for the Internet.

The DNS name space is managed by a number of organizations, including the Internet Corporation for Assigned Names and Numbers (ICANN), which is responsible for coordinating the allocation of unique domain names and IP addresses.

DNS Namespace Hierarchy

The DNS namespace is organized hierarchically, with the root of the hierarchy at the top. At the root of the DNS namespace, there are a number of top-level domains (TLDs), such as .com, .net, and .org. These TLDs are further divided into second-level domains, and so on.

For example, consider the domain name "example.com". "com" is the top-level domain, and "example" is the second-level domain. "Example.com" can have subdomains beneath it, such as "www.example.com" and "mail.example.com". Each subdomain can also have further subdomains beneath it, forming a tree-like structure.

The DNS namespace is decentralized, meaning that there is no central authority that controls the entire namespace. Instead, different organizations are responsible for managing different parts of the namespace. For example, ICANN is responsible for coordinating the allocation of unique domain names and IP addresses, while individual registrars are responsible for selling domain names to customers and maintaining records of those domain names in the DNS.

DNS Hierarchy in a Local Domain

In a local domain, the DNS hierarchy can be used to organize the domain's resources and make them easier to find. For example, a local domain might have a structure like this −

Root domain: example.local
   Subdomain: servers.example.local
   Subdomain: clients.example.local
   Subdomain: printers.example.local

In this example, the root domain is "example.local", and there are three subdomains beneath it: "servers.example.local", "clients.example.local", and "printers.example.local". Each of these subdomains can contain resource records that describe the resources within that subdomain.

For example, the "servers.example.local" subdomain might contain resource records for the domain's servers, such as their hostnames and IP addresses. The "clients.example.local" subdomain might contain resource records for the domain's client computers, and the "printers.example.local" subdomain might contain resource records for the domain's printers.

By organizing the resources in a local domain using the DNS hierarchy, it becomes easier for users to locate and access the resources they need.

DNS Hierarchy and the Internet

The DNS hierarchy is used to organize domain names on the Internet as well. At the top of the Internet's DNS hierarchy is the root domain, which is represented by a single dot ("."). Below the root domain, there are a number of top-level domains (TLDs), such as .com, .net, and .org. These TLDs are further divided into second-level domains, and so on.

For example, consider the domain name "example.com". "com" is the top-level domain, and "example" is the second-level domain. "Example.com" can have subdomains beneath it, such as "www.example.com" and "mail.example.com". Each subdomain can also have further subdomains beneath it, forming a tree-like structure.

The DNS hierarchy on the Internet is decentralized, meaning that there is no central authority that controls the entire namespace. Instead, different organizations are responsible for managing different parts of the namespace. For example, ICANN is responsible for coordinating the allocation of unique domain names and IP addresses, while individual registrars are responsible for selling domain names to customers and maintaining records of those domain names in the DNS.

Domain Names

A domain name is a unique name that identifies a website or other resource on the Internet. Domain names are used to locate and identify resources, such as websites, on the Internet. They are made up of a series of labels separated by periods (also known as "dots"), and are organized in a hierarchical manner.

For example, the domain name "example.com" is made up of two labels: "example" and "com". The "com" part of the domain name is known as the top-level domain (TLD), while "example" is the second-level domain. Domain names can also have subdomains, such as "www.example.com" or "mail.example.com".

Domain names are used in conjunction with the Domain Name System (DNS) to locate resources on the Internet. When you type a domain name into your web browser's address bar, your computer contacts a DNS server to translate the domain name into an IP address, which is then used to locate and access the desired resource.,

Domain names are typically registered through a domain name registrar, which is an organization that is accredited by ICANN (the Internet Corporation for Assigned Names and Numbers) to sell domain names to the public. Domain names can be purchased for a fee, and are typically registered for a period of one to ten years.

Fully-Qualified Domain Names

A fully-qualified domain name (FQDN) is a domain name that specifies the complete path to a particular domain in the Domain Name System (DNS) hierarchy. An FQDN consists of a series of labels separated by periods, and includes the top-level domain (TLD) at the end.

For example, the FQDN "www.example.com" specifies the domain "www" within the "example.com" domain. The FQDN "mail.example.com" specifies the domain "mail" within the "example.com" domain.

In order for a domain name to be fully-qualified, it must include the entire path from the root of the DNS hierarchy to the specific domain. This means that it must include not only the top-level domain, but also all intermediate domains and subdomains.

FQDNs are used to uniquely identify a domain within the DNS hierarchy and to locate resources on the Internet. They are often used in combination with the Domain Name System (DNS) to translate domain names into IP addresses, which are then used to locate and access the desired resource.