DNS servers are scattered all over the Internet rather than having a single, central database. This helps to protect the Internet by not providing a single point of failure that could take down everything. It also helps speed up processing and reduce the time it takes for translating the names by dividing the workload among many servers and placing those servers around the globe. In this way, you get your address translated at a DNS server within miles of your location which you share with a few thousand hosts rather than having to communicate with a central server half way around the planet that millions of people are trying to use.
Your ISP (Internet Service Provider) most likely has their own DNS servers. Depending on the size of the ISP they may have more than one DNS server and they may be scattered around the globe as well for the same reasons cited above. An ISP has the equipment and owns or leases the telecommunications lines necessary to establish a presence on the Internet. In turn, they offer access through their equipment and telecommunication lines to users for a fee.
The largest ISP’s own the major conduits of the Internet referred to as the “backbone”. Picture it the way a spinal cord goes through your backbone and acts as the central pipeline for communications on your nervous system. Your nervous system branches off into smaller paths until it gets to the individual nerve endings similar to the way Internet communications branch from the backbone to the smaller ISP’s and finally down to your individual host on the network.
If something happens to one of the companies that provide the telecommunications lines that make up the backbone it can affect huge portions of the Internet because a great many smaller ISP’s that utilize that portion of the backbone will be affected as well.
This introduction should give you a better understanding of how the Internet is structured with the backbone providers supplying communications access to the ISP’s who in turn supply that access to the individual users such as yourself. It should also have helped you understand how your computer relates with the millions of other “hosts” on the Internet and how the DNS system is used to translate “plain-English” names to addresses that can be routed to their proper destinations. In the next installment we will cover TCPIP, DHCP, NAT and other fun Internet acronyms.