Il domain name it is the mnemonic name that is usually used to reach a remote server without knowing the corresponding public IP address. Take the address for example www.google.it or, more simply google.it (without www). The correspondence between mnemonic address and IP is managed by a DNS server, also called resolver DNS. The command nslookuptyped from the terminal window, allows you to resolve any domain name.
A period at the end of the domain name is not an error: here’s why
Some users have noticed that clicking on a name Hello from the Apple Safari browser, the presented URL contains a point at the end of the domain name. Is this a bug? The short answer is no. Below we explain why.
The Bonjour protocol, also known as Service Discovery (DNS-SD), was developed by Apple and allows devices and services to automatically discover and communicate with each other over a local IP network without the need for manual configuration by the user. Adding a period to the end of your domain name, however, is not exclusive to Bonjour.
Try manually inserting a period at the end of the domain name of whatever site you are visiting. You will verify that the site will load normally.
It is a little known fact, but the so-called domain names fully-qualified they have a period at the end. Those who personally manage a DNS server are aware of this aspect but the majority of users and most IT administrators do not know it.
The RFC 1034 specification, dating back to 1987, explicitly clarifies that every fully qualified (often called “absolute”) domain name ends with a period. For example, try typing blog.google. (with the final period): you will see that the request will be perfectly handled.
The difference between a domain name absolute and relative, in practice
Using a domain name with or without a trailing dot has a significant impact on its interpretation and resolution within the DNS system (Domain Name System).
When you use a domain name without a trailing point, the DNS server treats the name as relative to the user’s local context or DNS search domain. This means that the system will automatically add the specified search domains (such as those configured in the system’s DNS search list) to complete the domain name before attempting to resolve it.
For example, if you type blog.google and the search domain is set to “mydomain.com”, the system will try to resolve blog.google.mydomain.com.
Adding a trailing period to the end of your domain name tells the DNS system that the name is complete and fully qualified. In this case, DNS does not automatically add the local search domain or other specified domains before attempting resolution. The full domain name is used exactly as entered, without modifications or additional completions. For example, blog.google. it is considered an “absolute domain name” and is resolved without adding any search domain.
On the application side, absolute domain names are not always correctly handled
Although it is little known, the management of absolute domain names at the resolver DNS It is a must”. On the application side, however, if you enter a domain name with a trailing period in the browser’s address bar, various behaviors may occur.
In some cases, such as with google.com., a redirect occurs to the domain name without a period; in other cases the domain name fully-qualified is managed as if it were completely separate (for example, the disclaimer for accepting cookies, as if it were the first time you visit the website).
Still, in some situations, webmasters make obvious mistakes, with the failure to load JavaScript codes and style sheets. For example, try typing www.apple.com. and check what happens: at the time of writing, many elements of the Apple site will not load completely. Yet it is the company with the largest market capitalization in the world.
Opening image credit: iStock.com – gorodenkoff