Tag Archives: DNS cache

Is DNS cache important?

What is DNS cache?

The DNS cache is a temporary cache memory for storing DNS records of previously queried domain names. A lot of devices hold such memory mechanisms, such as DNS recursive servers, computers, tablets, mobiles, etc.

The idea behind it is for easy and fast DNS lookup, which is not necessary to repeat every time a particular domain name is requested. Let’s take, for example, the news website you visit every morning. The first time you requested to visit it, a DNS lookup was performed for the corresponding IP address. After the DNS recursive server stored its IP address, you were able to explore the website. Additionally, the DNS records were kept in the DNS cache. The next day when you open and search for the same website, the DNS resolver receives the available IP address from its DNS cache. Thus, it was not necessary for a new DNS lookup to be performed.

It is important to note that all the DNS records associated with the various domain names are going to be available in the DNS cache temporarily. Exactly how long time it is going to depend on the TTL (time-to-live) value, which the administrator sets.

The DNS queries of the users are able to receive a quicker answer and, also this mechanism helps with the efficient optimizations of the resources. 

How does it work?

It is a really helpful and important mechanism that saves a lot of time and Internet bandwidth. Let’s explain a little bit more about it and how it happens while following one DNS query. Every time when a user wants to visit and explore a domain name, it is essential to know the A or AAAA records for it.

  1. The first place to check it is the device’s own DNS cache. On every computer is stored a file that saves earlier visited domain names for a specific amount of time (TTL). Thus, the website will load without any DNS query to a DNS resolver if the data is still available there.
  2. In case the data is not available in the device’s cache, a query is performed to a DNS resolver, such as the one in your Internet service provider (ISP). If it is still stored there, it will answer the request, and the user will connect with the website without any further steps. If this is not the case, then a search through the root server, the TLD server, and lastly, the domain’s authoritative server is going to be performed.
  3. Once the required DNS records are found, they will be kept inside the DNS cache of the user’s device and the DNS resolver too. That is good news because next time the website is going to be faster and easier to visit.

The DNS resolver of an ISP will store DNS records of every explored domain name of each of their customers that requested it for an answer. For that reason, the chance is better to hold the answer in the cache memory for the next time someone requests a domain.

Why is DNS cache important? 

As we mentioned, the DNS cache is an effective mechanism for producing a faster and efficient DNS resolution process. It saves time, effort, and sources both for the network and the user’s device. The use of it is very appreciated for its characteristics.