Remembering someone’s name is a lot easier than remembering their phone number—words stick in our brains better than numbers. But knowing a person’s name isn’t much use when you’re trying to get a hold of them.
Remembering someone’s name is a lot easier than remembering their phone number—words stick in our brains better than numbers. But knowing a person’s name isn’t much use when you’re trying to get a hold of them.
Like a computer, you use numbers to communicate, but you wouldn’t memorize all of your friend’s phone numbers for the same reason you wouldn’t memorize the IP address of every web page you visit. Thanks to DNS—the internet’s phone book—you don’t have to.
DNS is an integral part of everything you do online, and while it might seem complex, there are simple ways to think about it. The next sections explain what DNS is and cover a bit about how it works.
DNS stands for Domain Name System. In a general sense, it acts as the internet’s directory, and lets you connect to websites using words instead of numbers.
In the 1970s, if you wanted to add a new address to the fledgling internet, you had to call Elizabeth “Jake” Feinler at the Stanford Research Institute. She oversaw the directory of the first public packet-switched computer network, called ARPANET. At your request, Feinler would manually add your new domain name and its corresponding numerical address in a single file called ‘HOSTS.TXT’.
By the late 1980s, Feinler’s central address directory became too cumbersome to maintain, and the Domain Name System (DNS), which instead distributed the directory across multiple servers and locations, was created in its place. Since then, DNS has been consistently updated to accommodate the modern internet.
DNS is often called the phone book of the internet because it manages the mapping between names and numbers. To refresh this metaphor, think of DNS as the contacts app on your phone, which organizes and puts a name to the contact information of everyone you know. Thanks to your contacts app you can tell Siri, for instance, to “Call Mom” and your phone will dial her number; thanks to DNS, you can type ‘nytimes.com’ in your address bar and your web browser will reach the New York Times to display the latest headlines.
More specifically, DNS is a web service that translates a domain name, like ‘neeva.com’, into an IP address, like ‘231.230.78.12’, to connect to a website and load its resources. DNS makes internet communications possible by turning human-readable domain names into computer-readable numerical IP addresses. This way, you don’t have to remember complicated strings of numbers. Instead, you access information online through easily-remembered words and terms.
IP addresses are an essential part of all online activity. Without them, accessing the internet would be impossible. All internet-enabled devices—from servers, to computers, to phones—find and communicate with one another using these numbers. IP addresses identify where data should be sent in much the same way street addresses on packages and envelopes identify where your mail should end up.
To return your request, or query, with a website, DNS maps the domain name you type into your address bar to locate the associated IP address. This process is referred to as a DNS lookup. Web browsing relies on DNS lookups to quickly provide the necessary details, called DNS records, to connect you to a remote server, regardless of where you and the server are respectively located. A DNS lookup takes a fraction of a second, is imperceptible, and requires no interaction from your device aside from the initial query.
DNS is a globally distributed service, meaning it doesn’t exist on a single server—as Feinler’s directory did—but consists instead of a large distributed system of servers belonging to multiple entities across the web and around the world.
DNS is organized into small domains; no single server stores every domain. A server is responsible only for its domain, and knows to point to other servers, which are responsible for other domains. When a server gets a request about an address inside its domain, it provides the answer; when a server gets a request for an address outside of its domain, it forwards the query to another server.
To avoid going through this process multiple times for the same query, servers can cache, i.e. store, the information for a set amount of time. Caching improves load times, reduces bandwidth, and promotes efficiency. The length of time the DNS records are held, known as time to live (TTL), depends on various factors; longer periods lessen the load on servers, whereas shorter periods ensure more accurate responses.
Within DNS, access providers, including businesses, universities, governments, and other organizations, have their own assigned domain names and corresponding IP addresses, and run their own DNS servers to manage the mapping of those names and addresses. Most URLs, for example, are set up around the domain name of the server that takes user requests, e.i. ‘harvard.edu’ or ‘usa.gov’.
DNS isn’t only for web browsing. There’s a DNS lookup with all kinds of network requests that involve reaching out to a remote server, including software updates, mobile apps, and—for worse—malware. In each of these examples your device reaches out to a domain name rather than an IP address, so that if an IP address changes—which they sometimes do—you can still establish a connection to the server.
Servers across the globe maintain and deliver DNS records, including server names, IP addresses, and subdomains (like the ‘en’ in ‘en.wikipedia.org’). There are different types of DNS servers a query needs to pass between—each with different roles in the sequence that translates domain names to IP addresses:
To summarize and simplify, think of a DNS query like this: The recursive server asks for DNS records (including the IP address) on your behalf, and the authoritative server ultimately answers your query. The root and TLD servers handle your request as it travels between these two endpoints, and rarely provide records themselves. Each server plays a different role and is integral to the DNS infrastructure.
There’s also a distinction between public and private DNS. Organizations often use DNS internally for requests that involve reaching out to a remote server within their own network. This is called private or local DNS. Public DNS, on the other hand, refers to requests that reach out to the wider web, i.e. the internet.
To better understand how a domain name is translated to its corresponding IP address, it helps to follow a query along the DNS lookup process. Here are some of the basic steps in a typical query:
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