Managing Mission - Critical Domains and DNS

Domain names 101

You probably already know that a domain name is simply an alphanumeric string that is mapped—via the Domain Name System (DNS) to other data—like an Internet Protocol (IP) address.

So, asking, What is a domain? may seem self-explanatory. example.com is a domain.

However, when you get into the specifics of the DNS protocol and the documents that describe it, we start to run into some odd nuances in terms of what the formal specification of a domain is, versus what you can actually register online at some domain registrar as "your domain name."

For example, underscores are permitted in domain names. This is why certain types of records and practices use them. Later in this book, when we're examining SRV records, we'll see underscores. ...