Let us follow the DNS query starting from your computer. Your computer knows the address of a nearby DNS “caching server” and will send the query there. These caching servers are usually operated by the people that provide Internet connectivity to you. This can be your Internet Service Provider (ISP) in a residential setting or your corporate IT department in an office setting. Your computer may learn the address of the available caching servers automatically when connecting to the network or have it statically configured by your network administrator.

When the query arrives at the caching server there is a good chance that this server knows the answer already because it has remembered it, “cached” in DNS terminology, from a previous transaction. So if someone using the same caching server has sent mail to someone at ‘ripe.net’ recently, all the information that is needed will already be available and all the caching server has to do is to send the cached answers to your computer. You can see how caching speeds up responses to queries for popular names considerably. Another important effect of caching is to reduce the load on the DNS as a whole, because many queries do not go beyond the caching servers.