DNS Servers: What Are They and Why Are They Used?

The Domain Name System (DNS) is a naming system based on a distributed computer database for devices, computers, and any other element with an internet connection. It translates domain names that people can read (ex., facebook.com) into equipment-associated numerical identifiers, which lets users locate and connect devices worldwide.

DNS is analogical to the phone books, which are now becoming obsolete. They are their equivalent in the digital age. They link the domain to the server’s actual IP address, which holds the information the browser requests.

How do DNS Servers Work?

DNS servers hold and distribute the DNS directory globally. They are interlinked and communicate regularly to build redundancy and synchronize directory data.

A domain can have just one associated IP address, hundreds or tens of thousands. For example, eBay has thousands of servers all over the world. A customer uses one physical server in one country or geographical region, which is totally different from what another user in another country accesses. Internet services are global in nature, which necessitates a network of scalable and distributed DNS servers to make sure users can find the requested server’s location quickly, irrespective of where they are based.

Common DNS Issues

Given the complexity of DNS servers, it’s hardly a surprise that issues can arise. The most common ones include unresponsive servers, resolution failure, high latency, wrongly configured servers, and high Time to Live (TTL) values. 

Resolution failure

Resolution failure occurs when the server can’t link an IP to a domain name. The usual cause is network connectivity problems, wrong configuration, or an unregistered domain.

Unresponsive server

The “DNS server not responding” error manifests when the server’s configuration is wrong or the server is down. Poor network connection can also cause it.

High DNS latency

Latency means how much time data takes to reach its destination over a network and then return to its source. It’s measured in milliseconds (ms) and should be as low as possible. The higher the latency, the more time a site takes to load.

Latency is adversely impacted by network congestion. In addition, the server’s location is a crucial factor. Logically, latency is high when the user is far from the server.

Incorrect DNS configuration

Poorly or wrongly configured records cause DNS problems quite often. Mistakes in your records’ IP addresses and values lead to DNS resolution issues. Moreover, configuration mistakes in records make it impossible for the server to send and receive emails.

High TTL

The Time to Live (TTL) is how long a cached record should exist before a new one is requested. It is measured in seconds and set within each DNS configuration record. Usually, high TTL values are set for DNS records that don’t change often, like MX or TXT. However, a low value is needed for resources that undergo frequent updates. It is critical for website and network changes. The wrong setting can lead to downtime and high propagation waiting time.

You must understand how to use TTL properly to make the most of DNS resources and guarantee a satisfactory user experience. 

DNS Lookup

The DNS lookup process typically transpires in eight steps, which trace the information path between the server and the originating web browser. DNS lookup time is typically reduced by caching DNS information. The steps are outlined below in cases where the DNS information is not cached.

1. You enter the domain name (ex. apple.com) in your browser, which transmits the query to a DNS recursive resolver via the ISP.

2. The resolver then transmits it to the root DNS nameserver.

3. The root server returns the Top-Level Domain (TDL) address to the resolver. Examples of top-level domains are all those ending in “.com,” “.net,” and “.org.”

4. The resolver sends the data request to the TDL server.

5. The TLD nameserver responds to the resolver with the nameserver of the domain’s targeted IP address (the DNS server for “apple.com.”)

6. The resolver transmits the query to the domain’s DNS server.

7. The server returns the IP address to the resolver for the domain requested.

8. At the end, the resolver returns the domain’s IP to the requesting web browser. The browser sends the IP the HTTPS request. The server with that address returns the webpage, and it appears in the browser.