How DNS Cache Works

DNS cache is an essential component of the Domain Name System (DNS) that helps to speed up the process of resolving domain names to IP addresses. When a domain name is requested, the DNS resolver checks its cache for the corresponding IP address before making a query to the authoritative DNS server. This caching mechanism eliminates the need for repeated lookups, thereby reducing the latency and improving the overall performance of the DNS resolution process.

Here’s how DNS cache works:

When a user enters a domain name into their web browser, the resolver on their device queries the local cache to see if it has the IP address for that domain name. If the IP address is in the cache, the resolver returns it to the browser, and the browser connects to the web server directly. If the IP address is not in the cache, the resolver queries the DNS server responsible for the domain to obtain the IP address.

If the DNS server responds with the IP address, the resolver adds the IP address to its cache so that it can be retrieved quickly if the same domain name is requested again in the future. The time for which the IP address is stored in the cache is determined by the Time-to-Live (TTL) value, which is set by the domain’s administrator. The TTL specifies the duration for which the IP address can be cached before it is considered expired and a fresh query to the DNS server is required.

If the DNS server is unable to resolve the domain name, it returns an error to the resolver, which in turn returns an error to the browser. The browser then displays an error message to the user.

DNS cache is important for reducing the latency of the DNS resolution process and improving the user experience. However, it can also lead to some issues if the cached information is outdated or incorrect. This can happen if the TTL value is set too high or if the domain’s IP address changes frequently. In such cases, clearing the cache on the resolver or the device can help resolve the issue.

In conclusion, DNS cache is a crucial part of the DNS system that helps to improve the performance of domain name resolution by reducing the number of queries required to obtain IP addresses. While it can cause some issues if the cached information is outdated or incorrect, clearing the cache can help resolve these issues and ensure a seamless user experience.