What Is DNS Caching?

If a DNS Lookup sounds like it might take a few days, it doesn't. It may however take a few seconds. And it happens many times a day. It may occur several times before a full page can be displayed, if the page is composed of elements on different servers (ads, for example). There are times when the Internet is so congested that the wait is annoying. And if the DNS request requires a dial-up connection to be established, the browser may sometimes time out, requiring the user to renew the request. Every time the browser seeks a page on a website, the DNS lookup is repeated. If the user visits twenty pages on one site, the lookup is repeated twenty times. All for the same identical IP address. If the lookup takes three seconds, that is a total of sixty seconds spent waiting.

One solution to these delays is to store a copy of the domain names and their corresponding addresses in a computer on the LAN. This is called DNS caching. Retrieving an IP address from the local cache is almost instantaneous. This eliminates many delays and speeds up browsing for the end user.

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