What Is a Subdomain?by Fred Decker
Managing a large online presence can be a complicated undertaking, and it becomes ever more so as traffic to your domain grows. You can keep things manageable by purchasing multiple domains for different purposes or different parts of your enterprise, but that breeds additional costs and complications of its own. A more practical approach is the use of subdomains, a relatively quick and simple way to segment your traffic into meaningful streams.
Your site information is probably already broken down into multiple folders on your servers. Ordinarily you'd use links and menus on the site to route visitors to the information in these folders, or subdirectories. An alternative method is to create subdomains corresponding to those folders. A subdomain is simply a second website contained on your primary site, with a name that's a unique variation on the main URL. For example a company whose main URL is "ourcompany.com" might allocate subdomains called "accounting.ourcompany.com" or "products.ourcompany.com."
Subdomains vs. Subdirectories
The difference between a subdirectory URL and a subdomain URL isn't especially obvious to a layperson's eye, but it's an important distinction. A subdirectory's URL is expressed as "ourcompany.com/advertising/," while the same page as a subdomain would read "advertising.ourcompany.com." The subdirectory approach routes all incoming traffic through your main domain to the destination, increasing the workload on your main domain's servers. Each subdomain, in contrast, receives its own traffic individually.
Managing Server Traffic
The difference in the structure enables you to adapt rapidly to shifting or expanding traffic on any of your subdomains. If traffic increases sharply on one of your subdomains, you can scale up by simply adding server capacity. You can also use subdomains to provide load balancing, if you operate an especially popular site. In that case, the subdomains are for your own internal use. As traffic comes in, your load-balancing utility routes it to subdomains such as "ww2.ourcompany.com" or "ww3.ourcompany.com," where identical content is provided. This way no single server experiences slowdowns from extra-heavy traffic.
From the Marketing Side
Subdomains also create many opportunities for marketing and customer engagement. For example, you might create a Spanish version of your site at a subdomain such as "espanol.ourcompany.com," or create marketing sites for your distributors using the format "vendorsname.ourcompany.com." The same holds true for affiliations such as trade and industry organizations, or college alumni. Creating new subdomains for your marketing campaigns is another useful technique, permitting fast setup and reducing the risk of disruptions to your main site in the process.
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