[ Thanks to Pétur
Ingi Egilsson for this link. ]
“Your computer will need to lookup a website’s IP address every
time you visit it. The lookup request is passed on to the DNS
server(s) specified in the /etc/resolv.conf file. It will take the
server a few ms (milliseconds) at best to respond. It can take a
‘long’ time if your using a slow Internet connection (or a wireless
LAN).“Caching DNS acts just like a regular DNS, from the users point
of view. The service is configured to respond to lookup requests
and return IP addresses. If the Caching DNS does not know the
answer to the request, he will simply forward the request to the
correct server and then forward the reply to you once it has been
received. So what’s the difference?”