What is DNS

DNS stands for the Domain Name System, which is an essential part of the internet that syncs easy-to-remember domain names with their original IP addresses. In other words, DNS is a hierarchical and decentralized naming system for anything connected to a private network or the internet. Frequently labelled "the phonebook of the internet", DNS is often described as a global directory of human-readable names (websites) that match with numbers (IP addresses).

Every computer, laptop, smartphone, tablet, or website has an IP address like 63.103.179.156. When people want to access a certain webpage, instead of memorizing, searching, and typing its IP address, they just enter the associated domain name in their web browser (for instance, www.example.com). Domain names are made up of easy-to-remember words. Therefore, they are much simpler to remember and recognize than strings of numbers separated by dots – the language shared by computers. The role of DNS is to efficiently and safely locate the servers where each website is located.

At the beginning of the internet era - the late 1970s, early 1980s - site names and IP addresses were manually assigned by one person who kept an up-to-date list with all these associations - Stanford's Elizabeth Feinler, IT scientist. She used to update a text file called HOSTS.TXT with every computer that was connected to the internet. As the World Wide Web grew exponentially and Feinler only solved requests daily before 6 p.m., this process soon became unsustainable. A better solution had to be invented. The challenge was accepted by the USC researcher Paul Mockapetris who came up with his own new system called DNS that instantly translated IP addresses into domain names.

The converting process that links a domain like google.com to its designated IP number 173.125.13.56 starts with a simple query (also known as a DNS request) followed by a few steps:

1. Requesting for Website Information
   For instance, when we want to visit a website, www.infotracer.com, we type it in our web browser's address bar. Once we hit Enter, our device starts to resolve the hostname. First, it searches the name in its local DNS cache where all recent websites visited are stored.

2. Contacting the Recursive DNS Servers
   If the domain data is not cached locally, the device runs a DNS query with another server to find the right IP address to which the web browser can connect to and display the website to the requesting user.
3. Interrogating the Authoritative DNS Servers
   Many Internet Service Providers (ISPs) connect the end user's computer (DNS client) to recursive DNS servers (known as "recursive DNS resolvers" or "recursive resolvers"). If www.infotracer.com is not stored in their cache memory, the search continues up the hierarchy of authoritative name servers until it's found.
4. Accessing the A Record
   When tracing the IP address for Infotracer.com, we further query the authoritative DNS servers for the address record (A record) related to that domain. Recursive DNS name servers, access and store the A record for Infotracer.com from authoritative name servers right in their local cache. Next time someone wants to visit Infotracer.com, the recursive server will instantly know and display the answer. To keep data relevant, DNS data records are frequently updated.
5. Displaying the website
   Once the recursive DNS server has the information, it returns the A record. Our computer stores in its local cache the IP address from the DNS record and passes it to the web browser. The browser connects to the web server indicated in the A record's IP and displays the Infotracer.com website.

This entire process takes no longer than a millisecond to complete from start to finish.

DNS records (or "zone files") are instructions and details logged in authoritative DNS servers regarding web domains. Including websites' associated IP addresses and how to deal with requests for them, DNS records are usually series of text files written in DNS syntax. Their commands are formed from strings of characters that instruct DNS servers what to do. A Time-To-Live (TTL) is assigned to all DNS records indicating how often DNS servers should refresh them to keep the information relevant.

There are more than 40 types of DNS resource records, but the most common types are:

• A record (Host address mapping) - Holds a domain's IPv4 address and its hostname.
• AAAA record (IPv6 host address) - Stores a domain's hostname and corresponding IPv6 address.
• MX record (Mail eXchanger) - Directs e-mails to SMTP mail servers.
• CERT record (Certificates) - Stores PGP, SPKI, PKIX, and other encryption certificates.
• PTR record (Reverse-lookup Pointer) - Offers a domain name for reverse DNS lookups.
• NS record (Name Server) - Stores the name server for any DNS entry.
• SRV record (Service Location) - Provides the port for particular services.
• CNAME record (Canonical Name for an Alias) – Forwards subdomains or domains to other domains.
• TXT record (Descriptive Text) – Allows administrators to store text notes within the record (DMARC, DKIM, sender policy framework).
• SOA record (Start of Authority) - Keeps admin information about a domain (serial number such, admin's contact details).

Name servers are a key part of the whole DNS infrastructure. If we see the internet as a web of computers called servers that store and distribute websites to computers around the world, then a name server is a particular server managed by hosting providers or domain name registrars. Also spelled "nameserver", a name server's role is to keep DNS records of domain names and provide their corresponding DNS information to anyone who requests it.

When we type, for instance, www.infotracer.com in our internet browser, the request is received by the Infotracer's name server, which returns the IP address of the Infotracer website to our web browser. Every domain must have at least two, name servers – a primary one and a secondary one – for backup, in case the first fails to resolve the domain name. At the top of the DNS, hierarchy is the DNS root zone with root name servers. It includes the names and IP addresses for all the Top-Level Domain (TLD) names that share the same extension (".net", or ".com").