Domain Name System (DNS)
Domain Name System, commonly known as DNS, is an important mechanism that plays a pivotal role in making the Internet usable, accountable and user – friendly. We could go on for pages and pages explaining how DNS works, the history of DNS and how DNS is maintained and regulated. But this guide will focus on the aspects of DNS that affect you as a web user, network administrator or a webmaster.
Domain Names and IP Addresses
Before we discuss domain names, it’s best to understand what an Internet Protocol (IP) address is. The most commonly used analogy for an IP address is that of a telephone number. Just like every phone has its own unique phone number, every device – including computers, laptops, routers and web servers – has its own unique IP address. IP address is expressed as a set of four numbers separated by dots, e.g. 192.168.1.1 or 220.127.116.11. The IP address helps devices identify and locate one another on the network, such as Internet. For instance, when you navigate to Google from your computer, your web browser is in essence “dialing” one of Google’s IP addresses. In fact, try it right now: type 18.104.22.168 into your browser bar and see where it takes you.
Of course, it’s unpractical that we as users would memorize IP addresses of every website we visit. This is where domain names come into play. A domain name is not a location itself, rather, it points to an IP address or a set of IP addresses for larger websites. That way, when you type in “google.com” into your browser, you are redirected to one of Google’s public IP addresses, also known as IP range. How does your browser know where to redirect you? That’s where DNS comes in.
How does DNS work?
DNS is like a massive phonebook for all IP addresses. When you type in a domain name, your computer will first contact a name server to “look up” the IP address that corresponds to the domain name in a process called “Resolving DNS”.
Unlike a phonebook, however, DNS is not a centralized server that contains all the domains and the IP addresses on the Internet. DNS is built as a distributed database of independent name servers. Each name server is responsible for mapping a certain set of domain names to IP addresses. There’s a complex system of redundancies, overlaps and failovers, but all you need to know is that when you type in a domain from anywhere in the world, it will always point to the same IP address. As a requirement, every website is required to have at least two name servers, in case one is unavailable.
Besides resolving IP addresses used for web browsing, DNS servers may also contain other information, such as MX records, used for email traffic, and others.
Domain Names Registration
An added benefit for using domain names instead of IP addresses is that it allows a webmaster to use a permanent name for their website and at the same time choose where that website will be hosted. A webmaster can switch to a different hosting provider at any time, a process that will most likely result in an IP change but keeping the name of the website (domain name) the same.
Domain names can be purchased from a variety of accredited domain registrars, such as Godaddy, eNom or Moniker. It doesn’t matter which domain name registrar you choose – these registrars act like middlemen that record your registration with the global DNS.
After registering your domain name, you can choose to forward it to a URL or IP address of your choosing. Setting custom name servers is useful if you are on a shared hosting plan where you share an IP address with several other websites. By referring your domain name to your web host’s name server, it can then handle the task of resolving requests to your registered domain to your website’s IP. You can also create custom name servers that will handle DNS on their own.
Whois and DNS Lookup
When you register a domain name, you are required to enter some information about yourself or your company. This usually includes the name of your technical administrator, your mailing address and a telephone number. This information is kept by the domain registrar in its Whois database and is typically available to the public. This keeps webmasters and email users accountable on the Web. By performing a Whois request for any given domain, you can learn which domain registrar maintains the domain name (i.e. GoDaddy, eNom), who the registrant is (i.e. Google or Microsoft or Kraft Foods) and the technical and/or administrative contacts (i.e. the company’s attorney or CTO). Furthermore, you can learn the IP address that the domain name is associated with by performing a DNS lookup. This reveals the IP address, name servers, MX records and other information about the domain.
Whois and DNS Lookup are important tools for helping consumers, regulatory authorities and other web users understand where emails, web content and other IP traffic comes from.
In summary, this is what you need to know about DNS:
IP addresses are unique numerical identifiers for each device connected to the Internet. For example, 22.214.171.124.
Domain names are easy to remember, human-friendly entries that point to IP addresses. For example, Google.com.
DNS is the system that keeps track of all the domain names and which IP addresses they point to.
Note: Currently, we use a 32-bit IP address space, known as IPv4, such as those used in the examples in this article. But now, we’re running out of unique IPv4 addresses to assign. To solve this problem, the Internet has been transitioning to a 128-bit address space, known as IPv6, which is expressed as eight groups of four hexadecimal digits, e.g. 2001:0db8:85a3:0000:0000:8a2e:0370:7334. This transition will expand the number of usable IPs from roughly 4.2 billion to 340 undecillion, which translates to more than the number of visible stars per every living person.