Say "Webster" to an ordinary person
(that is, a person whose life has not been taken over by computers! <g>) and
they may think of the dictionary man, or perhaps the playwright John Webster,
but we, of course, know that the word is really the name for those noble
individuals who devote a part of their life to the propagation of human
knowledge and culture by designing and creating web sites on the Internet!
Names are like that. They have different meanings to different people.
There is one set of names, however, that is a little different. This set has a
specific meaning. While they may be based on words or names in one of this
planet’s spoken languages, they designate specific locations on the Internet,
and are therefore held in high esteem by the aforementioned Websters. They are,
as you have already surmised, Domain Names.
"Ah yes," you nod knowingly, "Domain Names." But do you really know what a
"Domain" name is and how it works? Many of you do, I’m sure, but it is
surprising to me how many questions I am asked that have to do with them, so I
thought a little closer look might be a good idea.
Mr. Webster, the dictionary man, tells me that a Domain is "the possessions,
estate or land belonging to one person." On the Internet, real estate takes on a
slightly different hue. An Internet Domain is a collection of addresses
controlled by one server (under the direction, presumably, of a Server
Administrator!) A Domain Name’s purpose in life is to provide an easy to
remember way of discovering a numerical internet address. It accomplishes this
through the Domain Name System (DNS) which is a clever, distributed system
(meaning it is made up of a lot of computers working together) for translating
the name into an address. The translation process is called "Resolving" a Domain
Name. A computer involved in the DNS system runs a program called a DNS Resolver.
Here’s how it works:
A domain name is made up of two parts, separated by a period, like this:
domainname.com Technically, this is actually two domains, as you will see, but
that’s too picky for this type of description! The part following the period is
known as the Top Level Domain, or TLD. In this example the TLD is com — known
as "dot com" because it always follows the period (dot). Every DNS Resolver has
addresses for "Root" DNS resolvers. These Root resolvers point to computers that
can resolve the Top Level Domains. In our example, they would point to one that
knows about ".com"s, which would in turn have the address of the system that
knows about "domainname". The ".com" resolver is given the information about "domainname"
when "domainname" is registered as "domainname.com". This updating is performed
by a group of service providers known as "Domain Name Registrars". You go to a
Registrar and register your domain name. When you do, they update the TLD
resolvers.
Part of the information required in the registration process is the name of the
DNS resolver(s) that will hold information about domainname.com. The first of
these is called the Primary DNS Server. Information about the domain is updated
in the Primary DNS Server, which will then provide this to "Secondary" DNS
Servers that will hold a copy of the information for use in the event the
Primary becomes unavailable. The TLD servers usually require information about a
Primary and at least one Secondary DNS Server, though several Secondaries can be
provided.
The Primary DNS Server (and subsequently, the Secondaries) stores information
about addresses within the domain. One of the types of address that can be
stored is a "Host" address. There are several others, but that’s a story for
another day! A Host is usually a particular computer. For example, you could
have a hostname called "www" (which is very common!) Taken from the initials of
the World Wide Web, this name is frequently used to point to a computer that
houses (hosts) the web site for the domain. By "point to", I mean that the name
is associated with the address of the computer. This association allows a DNS
Resolver to translate www.domainname.com into the address of the computer
hosting the website. When you type "www.domainname.com" into the address bar of
your browser, the first thing the browser does is to use DNS to translate the
name into an address to which it can send a request for a web page.
In this way, the Primary DNS Server for a Domain controls all addresses within
the Domain. By the way, a Domain can contain a "Sub-Domain" — as in
sub.domainname.com — which in turn contains Hosts, such as
www.sub.domainname.com That too, is a story for another day. Think about
it though, and you will probably be able to figure out how it works!
