Introduction To Network Communications - Part 2

By: Daniel Imbellino
Updated: Feb 21, 2013

What is a domain? You see websites on the internet all the time, and you see sites that end in .net, .com, .gov, .info. us, etc. These are called “Top Level Domains”, and they are the names assigned to logical addresses of entities across the internet. Add a www. and a name to the dot-suffix, and you have a “Fully Qualified Domain” name, such as Just as the .com is the “Top Level Domain”, WWW is the “Host” name. This sites name is PCTECHAUTHORITY.COM, which is infact a domain name. The “PCTECHAUTHORITY” part is the “Second-Level” domain. Then there are also “Sub Domains.” Sub domains are used typically by large organizations that need to divide up their resources into particular categories that can referenced directly over the internet. For instance, Microsoft likely has more sub domains than any other organization I’ve come across so far, such as for example. As the world continues to flourish with mobile devices, many organizations are creating mobile versions of their sites for access on the internet. For instance you may see a website like (the fully qualified domain name) and then when connecting from your smart phone you would see the address as The “mobile” part is the sub domain, “example” is the second level domain, and “.com” is the top level domain. A contact for a particular person could also be a sub domain, such as In this case Microsoft is the name of the network that Kathy resides on. Each dot in this sense actually represents a separate directory within a given network.

Today many organizations are dropping the WWW and just sticking with the second level and top domains. There are a few ways to reference a website when searching the internet. One way is to use “http:// prefix followed by the domain name, such as, which is the fastest and easiest way to reach our site directly over the internet using your browsers main search bar. Or you could use, or, or by search engine, just use the domain name "PCTECHAUTHORITY.COM." HTTP means “Hyper Text Transfer Protocol”, and is the protocol used to communicate with websites over the internet.

On the next page we will take a look at the OSI Reference Model, which will give us a good example of how computers and other internet resources communicate over the internet. Then we will take a look at the fundamentals of IP addressing.