What is DNS

In this article, we have covered topics related to DNS like: what DNS is, how does DNS works. We have also discussed about types of DNS queries.

Basics of DNS

Domain names are converted to IP addresses via the Domain Name System (DNS), which browsers utilise to load internet pages. Every internet-connected device has a unique IP address that other devices can use to find the connected device. People may enter common english words into their browser’s address bar, like skilledengg.com, thanks to DNS servers, saving them from having to remember the IP addresses of every website.

What is a DNS Server

The public IP addresses linked to the names of the websites that an IP address directs a user to are stored in a database on a computer known as a DNS server. DNS functions as an online phonebook.

The DNS determines the correct IP address whenever users type domain names like skilledengg.com or Yahoo.com into the address bar of web browsers. The device is directed to the proper location to access the site’s data by the IP address of the website.

When the DNS server discovers the right IP address, browsers use it to transfer data to origin servers or edge servers of content delivery networks (CDNs). The user will then be able to access the website’s information. The universal resource location (URL) for a website is first looked up by the DNS server in order to determine the appropriate IP address.

How DNS Works

DNS servers translate URLs and domain names into computer-friendly IP addresses. They convert human input into something a computer can understand in order to locate a webpage. This entire process of translation and lookup is called DNS resolution.

There are four following servers, which cooperate to deliver the right IP address to the client:

  1. Recursive DNS
  2. Root nameserver
  3. TLD nameserver
  4. Authoritative nameserver
  1. Recursive DNS: The DNS client sends the request to the Recursive DNS, also known as a DNS resolver. To find the correct IP address, it then interacts with other DNS servers. After retrieving the request from the client, the resolver mimics the behaviour of a client. While doing so, it issues requests to the authoritative nameservers, top-level domain (TLD) nameservers, and root nameservers, which are the other three DNS servers. This can be thought of as a librarian being requested to locate a specific book in a library.
  2. Root nameserver: The DNS hierarchy is headed by the root nameserver, often known as the root DNS server. Consider it a database of references. It doesn’t keep the information about the ip address which we are looking for. But, it gives directions to where it can be found.The root nameserver will determine the domain name’s top-level domain after receiving a request from the recursive DNS resolver. It will then instruct the recursive resolver to access the appropriate TLD nameserver. It can be thought of like a library’s index that directs users to certain book shelves.
  3. TLD nameserver: The DNS server function known as the TLD nameserver is in charge of keeping track of and managing data on domain names that utilise a particular top-level domain (TLD). A TLD, such as.com,.org,.online, and.net, is the final part of a domain name. The root nameserver will route the DNS recursive resolver to the.com TLD nameserver if your query is to determine the IP address of skilledengg.com. The TLD nameserver will then let the resolver know where the matching IP address is located at a particular authoritative nameserver. You might see the top level domain server (TLD) as a particular shelf of books in a library.
  4. Authoritative nameserver: The authoritative nameserver is the last stop in the nameserver query. An authoritative nameserver is what gives you the real answer to your DNS query. These servers manage the subdomain portion of the domain name and are completely knowledgeable about a certain domain. These servers hold DNS resource entries, such as the A record, that provide detailed information about a domain. They deliver the required record to the recursive server, which then sends it back to the client and caches it nearby for later lookups. The recursive resolver will obtain the IP address and send it back to your computer, directing you to the site. The domain name system resolver also performs DNS caching, temporarily storing IP addresses gathered from reliable nameservers. In other words, DNS caching enables a website to simply transmit back the IP address match that was previously received when you want to visit it again.

Steps of a DNS Lookup

The following steps make up the fundamental process of a DNS resolution:

  • A web address or domain name is typed into a browser by the user.
  • To determine which IP or network address the domain refers to, the browser sends a message to the network known as a recursive DNS query.
  • A recursive DNS server, also known as a recursive resolver, receives the request; these servers are typically run by internet service providers (ISPs). The user will receive the address back if the recursive resolver has it, and the website will load.
  • The authoritative name servers, top-level domain (TLD) name servers, and DNS root name servers will all be consulted if the recursive DNS server is unable to resolve the issue.
  • Together, the three different server types continue to reroute traffic until they locate a DNS entry that has the requested IP address. The user’s desired website loads after this information is sent to the recursive DNS server. DNS root name servers and TLD servers mostly redirect requests rather than solving problems directly.
  • The A record for the domain name, which includes the IP address, is kept in the recursive server’s cache. The following time it gets a request for that domain name, it can answer to the user directly rather than asking other servers for information.
  • If the query is sent to the authoritative server and it is unable to locate the data, it returns an error.

Types of DNS Queries

The most prevalent DNS requests that occur at various stages of DNS resolution are those listed below:

  1. Recursive DNS Queries: Recursive DNS queries are those that go back and forth between the client and the recursive server. Either the full name resolution or an error message stating that the name cannot be found is sent as the response. Recursive queries either produce the correct response or an error.
  2. Iterative DNS Queries: Iterative DNS queries are exchanged between the root, TLD, and authoritative name servers, which are nonlocal name servers, and the recursive resolver, a local DNS server. The name servers may provide a reference in response to iterative requests rather than a name resolution. The TLD refers the recursive server to an authoritative server after being referred by the root server to the TLD. If the authoritative server has the domain name, it gives it to the recursive server. Both a response and a referral are possible outcomes of iterative questions.
  3. Nonrecursive Queries: Nonrecursive queries are ones for which the answer is already known to the recursive resolver. Either the recursive server has the answer in its cache or it is aware to bypass the root and TLD servers and go directly to a certain authoritative server. There is no need for more queries, hence there is no request for them, making it nonrecursive. Nonrecursive queries have a solution. It is a nonrecursive query if a recursive resolver serves an IP address from a prior request that it has cached from a previous session.

Common DNS Records

A query looks for information in DNS records. Different information is needed depending on the query, client, or application. Some records, like the A record, must be kept.

There are numerous sorts of DNS records, each serving a specific function in indicating how a query should be handled. These common DNS records are available:

  1. A record: This contains a domain’s IP address and stands for “address.” For IPv4 addresses only, A records are used. Instead, IPv6 addresses contain AAAA records, which make advantage of the lengthier format. The majority of websites have just one A record, however some larger sites have numerous, which aids in load balancing by sending several A records to various visitors during periods of high traffic.
  2. NS record: These name server records identify the authoritative server in charge of maintaining all the data for a specific domain. To boost reliability, domains frequently have both primary and backup name servers, and several NS records are used to point queries at them.
  3. TXT Record: Administrators can enter text into DNS using TXT records. Although machine-readable annotations are now frequently added to DNS, human-readable remarks were the original intention. TXT records are used to safeguard email, prevent email spam, and verify domain ownership.
  4. CNAME Record: When there is an alias, canonical name records are utilised rather than an A record. They are utilised to retry the same IP address’s query with two alternative domains. As an illustration, the CNAME would query techtarget.com in the URL searchsecurity.techtarget.com.

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