10 March 2010

The parts to a domain name in web addresses: Quick intro

Having never registered a domain name before, I had set out to learn how and what's involved. Sure I used domain names a lot in that I go to many web pages by typing in an address, but I have never looked fully into the mechanics behind domain names.

Here I'll explain what I learned, mainly the generalities behind what domain names are and how they work. I was dismayed by some recent news on how confusing domain names can be, so it may be helpful for you to understand how they work too.

Let's start!

Each web page you see on the world wide web is located somewhere, and so has an address. This web address is called its URL or URI (the specifics are rather technical). You should see this blog post's URL in your web browser above as:

http://blog.carsoncheng.ca/2010/03/parts-to-domain-name-in-web-addresses.html

There are a number of parts to this address that are separated by the slashes (ie, the forward slashes).

The http part tells the computer to use the Hypertext Transfer Protocol when accessing the page you want. There are other protocols too, but normally most everything uses http. If you are on a log-in page somewhere though, especially when you do online banking, the protocol should be https (note the "s"), as in the Hypertext Transfer Protocol Secure.

The :// ("colon slash slash") then tells where the rest of the address begins.


You see the blog.carsoncheng.ca part? That's the authority you're asking to get the web page from, and that's the part containing the domain name. We'll come back to it because it has a number of parts too, separated by the dots (ie, periods).

After the authority, there is the 2010/03/... That's the path to the web page you want to see. We won't go into that in this post though, because it's not part of the domain name.

Back to the authority, which is commonly just called the "domain name," although that's not quite right. There are three parts to it separated by the two periods: (1) blog, (2) carsoncheng, (3) ca.

The third part, the ca, refers to the top level domain (TLD). It could have been com (as in a "dot com" address), net (as in a "dot net" address), or something else altogether. It just depends on how it's registered.

There are generally two broad types of TLDs: country code (ccTLD) and generic (gTLD). My "dot ca" is a ccTLD, ca representing Canada. The "dot com" or "dot net", etc, are examples from gTLD. How does this affect you? Well if you are looking to register a domain name, you'll find that only certain registrars could register a ccTLD for you (namely the registrars allowed by that country). On the other hand, generic TLDs may be registered by pretty much all registrars, and so are more popular.

Next is the second part, the carsoncheng part from blog.carsoncheng.ca. That's the domain label [1]. You get to choose that, so long as it's unused within the chosen top level domain (TLD). The domain label together with the TLD forms the hostname, sometimes also called the "domain name" (in this case, carsoncheng.ca) depending on who you talk to.

Finally, the first part (yes, it's backwards compared to the rest of the URL address). The blog (of blog.carsoncheng.ca) is called the subdomain. Most registrars should let you have many subdomains under your domain name, and let you direct those to different places.

For example, in the future, I might have carsoncheng.ca land on a front entrance page with pretty photos. While blog.carsoncheng.ca brings you here, to this blog. Perhaps I'll set up shop.carsoncheng.ca to land on my shopping site, etc.

I've seen a trend away from using subdomains though (Apple used to use them a lot, but they seem to have integrated the subdomain names into the paths instead, as has a lot of other sites I see). Maybe it's because of the backwards (right to left) nature of the dot separated domain name grammar, versus the straightforward (left to right) nature of the path. Who knows.

Why would you care about subdomains?

Well, you might care about subdomains because you might be using some web services hosted elsewhere that you want your subdomains to forward to. For example, I could set up two blogs in Google Blogger (say cookingblog and photoblog), and assign them different subdomains [2], ie, cookingblog.carsoncheng.ca and photoblog.carsoncheng.ca.  That might be useful for you.

So that's a quick introduction to the language of domain names! The details get technical fast, but everyone should have a working understanding of web page addresses. For more details, reading into it on Wikipedia would be a good next step.

[1] I find the terminology to vary from time to time depending on who you ask for these things. As long as we know what we're talking about and can give examples, I guess it doesn't really matter so much for non-technical uses. For technical users, they can give and use the grammar for those things, say by reference to the specifications and other documents.

[2] I confess I have never tried this, but it seems to be possible given what I saw of the set-up pages on Google Blogger. Please let me know if this doesn't work.

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