You can see that this process involves a lot of individual steps to go from initial query through to full completion. But you may also be wondering, "If there are so many steps involved with this process, why do my DNS names resolve so quickly?" The strict hierarchy of DNS servers is necessary to support its extensibility, and the communication between the servers in that hierarchy can take some time, especially when there are multiple levels to the query.

DNS's "speed" comes from the second bullet point above - its local cache. Every time a DNS server completes a request, it stores a copy of that record in its local cache for a period of time (12 hours by default in Server 2008). When it receives a query for an address, it first checks that cache. This gives it the ability to respond almost immediately for some already-resolved addresses.

A cache also exists on the client as well, with individual records being stored there for one day (86,400 seconds) by default. It is possible to view the local client cache by using the command ipconfig /displaydns. The result looks similar to Figure 2 with each entry showing the record name and time to live in addition to other data.

For such a set-it-and-forget-it service, DNS still involves a lot of moving parts. As you can see here even the simplest processes of DNS resolution involves the interworking of clients with numerous servers all across the Internet.