Domain Basics
A Domain is a core concept in internet addressing. It is a human-friendly name created to allow users to easily remember and access websites. It is closely tied to the DNS (Domain Name System).
1. Components of a Domain Name
A domain name has a hierarchical structure, where components become more specific from right to left.
| Component | Technical Term | Description | Example (based on www.google.com) |
|---|---|---|---|
| Top Level | TLD (Top-Level Domain) | The rightmost part of the name, indicating the country (.kr) or purpose (.com, .org). | .com |
| Second Level | Second-Level Domain | The unique name registered by the domain owner. | google |
| Third Level | Subdomain | Used to distinguish specific areas or services within the website. | www (most common), mail, blog, etc. |
| Full Address | FQDN (Fully Qualified Domain Name) | The complete domain name, including the subdomain and TLD. | www.google.com |
2. How a Domain Works
Domains rely on the DNS (Domain Name System) to function.
- Input: The user enters a domain name (
google.com) into their browser. - Resolution Request: The DNS Resolver requests the IP address corresponding to this domain name.
- Name Server Lookup: The Resolver navigates through the Root Server and TLD Server, ultimately reaching the domain's Authoritative Name Server.
- IP Acquisition: The server provides the IP address based on the stored A Record (Domain $\leftrightarrow$ IP Address).
- Connection: The browser uses the retrieved IP address to connect to the server and display the webpage.
3. Importance of Domains
- Ease of Access: Allows access to internet resources via easy-to-remember characters instead of complex numerical IP addresses.
- Branding: Represents a critical brand asset and identity for a company or individual.
- Flexibility: If a web server changes its IP address, only the domain's A Record needs to be updated, and users can continue accessing it using the same domain name.