Every visit to a website is preceded by a process invisible to the user – the conversion of the address entered in the browser into a sequence of numbers understandable by servers. DNS, one of the foundations of the modern internet, is responsible for this.
In this article, we explain what this acronym stands for, how a DNS server works, what information it stores about your domain, and why changes to its settings don't take effect immediately.
DNS – a system that connects domain names with servers
DNS stands for Domain Name System. It's a distributed network service responsible for assigning domain names to their corresponding numerical server addresses.
Without DNS, to open a website, you would have to remember a string of numbers assigned to each website – instead of entering verseo.pl, you would have to know the exact address of the server on which it is hosted.
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Simply put, DNS translates human-readable names into addresses understandable by network devices. The system is designed to be hierarchical and distributed, meaning that no single server stores information about all domains in the world.
Responsibility is divided between thousands of cooperating servers around the globe, making the entire structure fault-tolerant and allowing it to quickly handle billions of queries per day.
How does a DNS server work? The principle of translating names into IP addresses.
When you enter a website address in your browser, your device doesn't immediately connect to the target server. It first has to determine the IP address corresponding to the entered name. This task is performed by a series of DNS servers operating according to a strictly defined pattern.
Typically, the process occurs in four stages. The computer first queries a local resolver—usually the ISP's server or a public resolver specified in the network settings. If this doesn't respond, it forwards the query to one of the root servers, which indicate where to look for information about the top-level domain, such as .pl or .com.
The query then goes to the TLD server responsible for a given extension, and from there to the authoritative server, which stores specific data about the searched domain and returns its IP address.
DNS query response time and optimization
This typically takes fractions of a second. Furthermore, once the answers are obtained, they are stored in the cache – both on the resolver and the browser side. This means that subsequent visits to the same website do not require repeating the entire query path.
Types of DNS servers and query types
The servers that make up the domain name system have different roles – each is responsible for a different stage of name-to-address translation. There are four basic types of DNS servers:
- resolver (recursive server) – accepts a query from the user's device and guides it through subsequent stages until a response is obtained,
- root server – indicates which server is responsible for a given top-level domain,
- TLD server – is responsible for a specific ending, e.g. .pl, .com, .eu, and directs to the authoritative server for a given domain,
- authoritative server – stores the target domain configuration data and returns the final response.
DNS queries are divided into two types:
- Recursive force the server to find the full response and forward it back to the sender.
- Iterative allow the server to respond with what it currently has – if it doesn't know the full solution, it indicates the next server to contact.
The most important DNS records and their uses
Each domain is assigned a set of DNS records that determine how it should be handled. These records contain information about where the website is located, where email should be routed, and what other services are associated with the domain.
These records are managed within the domain registrar or hosting provider's control panel. The most common records include:
- A – indicates the IPv4 address of the server on which the website is hosted,
- YYYY – equivalent to the A record for IPv6 addresses,
- CNAME – creates an alias of one domain name for another, it is used, among others, for subdomains,
- MX – specifies the server responsible for receiving e-mail in the domain,
- NS – indicates which authoritative servers serve the domain,
- TXT – allows you to add text data, is used to verify domain ownership and configure SPF, DKIM and DMARC, i.e. email security mechanisms,
- SOA – contains zone administrative information, including the primary authoritative server.
DNS propagation – what is worth knowing when making changes?
Changing DNS records—for example, when moving a website to a new hosting provider , connecting a new email server, or changing registrars—doesn't happen instantly. The new configuration must propagate across the network of servers that cached the previous version of the record. This phenomenon is called DNS propagation.
How long it takes for changes to propagate is primarily determined by the TTL (Time To Live) parameter set for the record. This determines how long servers and devices should cache the response before re-querying for the current value.
Propagation can take anywhere from a few minutes to as long as 48 hours. During this time, some users will already be able to see the new version of the website, while others will still be able to see the previous version. This is a natural consequence of the way the system works and should be factored into the schedule for any domain-related work.
DNS FAQs
DNS (Domain Name System) is a distributed domain name system. Its main function is to translate user-friendly names (e.g., verseo.pl) into numerical IP addresses that network devices can understand. This eliminates the need to memorize strings of numbers assigned to specific websites.
When you enter a website address, your query goes through four stages. First, it goes to a resolver (recursive server), then to the root server, then to the TLD server (responsible for, for example, .pl extensions), until it reaches the authoritative server, which returns the domain's destination IP address.
There are four main types:
- Resolver (recursive server) – accepts and handles the user's query.
- Root server – indicates the appropriate server for a given top-level domain.
- TLD server – directs traffic within a given domain ending (e.g. .com, .eu).
- Authoritative server – stores the target domain configuration and returns the final response.
- Recursive queries force the server to find the full, final answer and pass it back.
- Iterative queries allow the server to respond based on what it already knows, or to indicate the next server to ask about the issue.
- A / AAAA – indicate the IPv4 and IPv6 addresses of the server on which the website is hosted, respectively.
- CNAME – creates an alias of one domain for another (often used for subdomains).
- MX – indicates the servers responsible for receiving e-mail.
- NS – specifies the authoritative servers serving a specific domain.
- TXT – used to add text data (e.g. for domain verification and email security such as SPF, DKIM, DMARC).
- SOA – contains administrative information about the zone, including the primary authoritative server.
Propagation is the process of new domain settings spreading across the network (e.g., after a hosting change). Because servers and browsers cache data, the new configuration is not immediately visible to all users.
The propagation time depends primarily on the TTL (Time To Live) parameter setting, which determines how long information is stored in the cache. Typically, it lasts from several minutes to a maximum of 48 hours.
Summary
The above article covers the following topics:
- DNS is a system that translates domain names into addresses understandable to network devices, so that the user does not have to remember strings of numbers assigned to websites.
- The abbreviation DNS comes from Domain Name System, a distributed and hierarchical structure that handles billions of queries daily.
- A DNS query passes through a resolver, a root server, and a TLD server until it reaches an authoritative server that returns the domain's destination IP address.
- There are four types of servers in the domain name system – recursive, root, TLD and authoritative, and queries are divided into recursive and iterative.
- The most common DNS records are A, AAAA, CNAME, MX, NS, TXT and SOA – they are responsible for server addresses, aliases, mail handling, and domain verification and security.
- DNS propagation is the time it takes for domain configuration changes to propagate across the network. This is regulated by the TTL parameter and is important for hosting migrations or email changes.
