I mentioned in the topic discussing segments, networks, subnetworks and internetworks that the Internet is really the king of internetworks. After all, you don't get to be called “the” something unless you pretty much define it.

In fact, the Internet is not just a large internetwork, but substantially more. The Internet is defined not just as the computers that are connected to each other around the world, but as the set of services and features that it offers. More than that, the Internet defines a specific way of doing things, of sharing information and resources between people and companies. And though it might be a bit melodramatic to say so, to many people the Internet is a way of life. As Internet use and popularity exploded in the 1990s, many people realized that the techniques and technologies used on the Internet would be useful if applied to internal company networks as well. The term intranet was coined to refer to an internal network that functioned like a “private Internet”. It comes from the prefix “intra”, which means “within”. Of course, “inter” is the opposite of “intra”, so this makes some people think that an “intranet” is the opposite of an “internet”. In fact, most intranets are internetworks as well!

As if that weren't bad enough from a jargon standpoint, the buzzword buzzards then decided to take matters a step further. If an intranet is “extended” to allow access to it not only strictly from within the organization, but also by people or groups outside the main company, this is sometimes called an extranet. “Extra” of course, is a prefix that means “outside” or “beyond”.

So, an extranet is a type of internal, private Internet that, uh, well, isn't entirely internal. An extranet is an extended intranet, which is really a type of internet that works like the Internet. (You can start to see why I am not a big fan of these fancy terms. But then, I don't get to choose them; I just have to help you understand them!) An extranet isn't public and open to all—it is controlled by a private organization. At the same time, it isn't entirely private either.

As you can see, the lines between the Internet, intranets and extranets were pretty blurry from the start, and the concepts are rapidly blending into a diffuse mass of gray, as the whole computing world becomes more tightly integrated. For example, even if you have an entirely private intranet, you will want to connect it to the Internet to communicate with the “outside world” and to allow access to Internet resources. And an extranet may be implemented, in part, through the public Internet infrastructure, using technologies such as virtual private networking (VPN). I think you get the picture.

The key that binds all of these concepts together is that they all use “Internet technologies”, a term that is itself somewhat vague. This usually refers to the use of the TCP/IP protocol suite, which is the defining technology of the Internet, as well as the set of services that are available on the Internet.

The bottom line is that being told that a company has an “intranet” or an “extranet”—as opposed to a plain old boring “network”—doesn't tell you much at all. It is best not to rely on the slogans and instead look at the underlying characteristics of the network or internetwork itself. Furthermore, when designing such a network, focus on using the technologies and protocols that make sense—let the marketing people decide what to call it later. J