Domain Name Service (DNS)

Let us break down how the Domain Name Service (DNS) and domain registrars work together:

1. Domain Registrars - The Starting Point:
   • Domain Sellers: Domain registrars are companies accredited by organizations like ICANN to manage the reservation and registration of domain names (e.g., example.com).
   • Reservation: When you want a website, you go to a domain registrar (like GoDaddy, Namecheap, Google Domains, etc.) and search for an available domain name. If it's available, you can purchase the right to use that domain for a specific period.
2. DNS - The Address Book of the Internet:
   • IP Addresses: Computers on the internet fundamentally communicate using numerical IP addresses (like 192.168.1.1). These are not very human-friendly.
   • DNS as a Translator: DNS acts like a giant, distributed phonebook. It translates human-readable domain names into the IP addresses that computers need to locate each other.
   • Hierarchical System: DNS is a hierarchical system with different levels of DNS servers responsible for different portions of the domain name space.
3. Where the Registrar and DNS Meet:
   • Nameservers: When you register a domain name with a registrar, you need to specify the nameservers that will be responsible for handling the DNS records for your domain. These nameservers can be provided by the registrar themselves or by a third-party DNS hosting service.
   • DNS Records: The registrar helps you configure essential DNS records like:
     • A Records: Map your domain name to the IP address of your web server.
     • MX Records: Specify which servers handle email for your domain.
     • CNAME Records: Create aliases from one domain to another.

How It All Works Together

1. User Types in Domain: A user types your domain name (e.g., [www.example.com](https://www.example.com)) into their browser.
2. DNS Lookup: The browser contacts a DNS server (usually specified by their internet provider) to find the IP address associated with your domain.
3. Nameserver Consultation: The DNS server consults the nameservers that you specified when you registered your domain.
4. Getting the Address: The nameservers provide the IP address associated with your domain based on your DNS records.
5. Website Connection: The user's browser connects to the web server at that IP address, fetching your website.

In Summary
The domain registrar is where you purchase and manage your domain name. DNS is the system that translates that domain name into the computer-friendly IP address, and the registrar helps configure the DNS records to point traffic to the correct location.

Domain names are alpha strings used to identify a Web site. For example, Yahoo.com, or Whitehouse.org are domain names. However, the Internet truly identifies Web sites by its IP address (example: 334.483.45.12). So, each time a user types a domain name into their browser's and presses Enter, the domain name is sent to the Domain Name Server (DNS) for translation to its assigned numeric IP address.
Domain Name Services (DNS) are dedicated servers (also called a DNS: Domain Name Server) which hold a two-column list of all the domains and IPs on the Internet (and, additional information, as we will see later in this module). For the purposes of explanation, the list has been simplified below:

Zone	Definition	For Use By
.com	Commercial	Businesses
.edu	Education	Universities
.gov	Government	U.S. federal government agencies
.int	International	Organizations established by international treaties
.mil	Military	U.S. military
.net	Network	Network Providers, administrator computers, network node computers
.org	Organization	Non-profit and miscellaneous organizations

When you want to launch a Web site, you must register a domain and host it with a provider. Registration requires two things: selecting a name (such as fluxstorm.com) and the IP address to the Host site (the company's computer where the Web site will be stored). Once known, the registrar (Internic) broadcasts that information to every DNS on the planet.
Within about 24 hours, all DNS servers know the IP address to fluxstorm.com

Because every domain name request must be translated to an IP address, thousands of DNSs are used on the Internet. Since DNSs are dedicated computers, they tend to be costly. To pay for these costs, larger organizations sell access to their DNS. Since DNS is critical to the operation of the Internet providers tend to rent services from two DNSs for redundacy. The two DNSs used are referred to as primary and the secondary, and each one is designated by its IP address (not its domain name, as that would slow things down). For efficiency DNSs use a tiered approach when translating domain names. Smaller DNSs provide translation to a limited number of local providers (ISPs) and offer maximum speed response by only storing the domain names (and IPs) of only the most recently requested addresses. When a domain outside the list is requested, the local DNS makes a request to a larger regional DNS for the IP. If the regional DNS does not have it, the local DNS sends a request to an even larger DNS until the domain is located. Now you know why it sometimes takes a long time to display a site. It may be that your local or regional DNS did not have the domain name in its list.

DNS stores its information in tables, and each table is composed of records. Each record is composed of a host name, a record type, and an address.
In the next lesson, you will learn about the DNS structure.