A Telephone Book Analogy

A Telephone Book Analogy

Author’s note: This column was originally published on May 11, 2007, and only slightly updated it explains the worldwide outage of Facebook, Whatsapp, and Instagram that occurred on October 4, 2021.


The acronym “DNS” is short for “Domain Name Service.” This is the technology used to translate domain names such as yahoo.com to numeric IP address This technology was developed because hotmail.com is easy to remember whereas is not.


A “DNS Server” is the actual physical computer using the “Domain Name Service” to do the aforementioned translating. Practically every Internet Service Provider on earth has a DNS Server for their customers to use.


Think of a DNS Server as the internet equivalent of a phone book. When you need to call Charles Miller, you open the book and find that next to Charles Miller is a number 415-101-8528. Dial that number to initiate a conversation. The internet works similarly; look up the name in DNS then connect to the corresponding number.


DNS Servers are the electronic phone book of the internet, and every ISP has a copy. Every copy of this electronic phone book, at every ISP around the world, gets updated frequently.


All the DNS Servers in the computers of the thousands of internet companies around the world get their updates from the thirteen Root Servers supervised by VeriSign and ICANN (Internet Corporation for Assigned Names and Numbers). A discussion of the coordination and oversight provided by these organizations is beyond the scope of this article, but suffice it to say there is some degree of supervision.


Problems will sometimes result when the DNS Server you are using is not up to date or is otherwise malfunctioning. When this happens, you may find that you can go to but not to www.atencionsanmiguel.org. Those two addresses are the same, one translated the other not. Try it and will see for yourself.


When you type in an address such as www.gmail.com, your computer must use your DNS Server to resolve the address to its numeric equivalent. If your DNS Server were not functioning, you could not get to Facebook, that is unless you knew that www.facebook.com was If you knew that, you could still get through by typing those numbers.


Why? Continuing the telephone book analogy, you do not have to look up a number in the phone book every time you dial. If you already know the number, you can bypass the phone book. If you know the IP address of the internet web page you are trying to reach, you can bypass your DNS Server simply by typing in the number rather than the name.


Fortunately, having your internet provider’s DNS Server go down is not a frequent problem. If you suspect this might have happened though, you can confirm it by trying one of the numeric addresses in this article. If the numeric IP address works and the alpha address does not, then your DNS Server is the first thing to suspect.


Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 415 101 8528 or email FAQ8@SMAguru.com.