Domain Name System Basics and Operation

The Domain Name System (DNS) converts human-readable domain names into machine-readable IP addresses.


All computer systems on the internet, from your desktop or mobile device to the servers that serve data for large retail websites, use numbers to find and communicate with one another. These figures are termed to as IP addresses. You don't even have to recall and insert a series of numbers when you open a web browser and go to a website. Instead, you can enter a domain name such as example.com and still be directed to the correct page.


A DNS service is a widely dispersed provider that directly converts human-readable names into the numeric IP addresses used by computers to connect to one another. The DNS system on the internet functions similarly to a phone book because it manages the modeling between contact details. DNS servers convert name requests into numeric IP addresses, determining which server an operator will reach when they enter a domain name into their web browser. These requests are known as queries.


How DNS Works


Domain name system resolution transforms a domain name into a computer-friendly IP address (such as 192.168.1.1192.158. 1.38). Each gadget on the internet is assigned an IP address, and that contact information is required to locate the appropriate internet gadget, just as street contact information is used to locate a specific home. When a user requests a webpage, an interpretation must occur between what the operator types into their internet browser and the machine-friendly address required to pinpoint the example.com webpage.


To comprehend the process of DNS resolution, it is necessary to first learn about the various hardware components that a DNS query should pass through. Except for the initial request, the DNS lookup takes place "behind the scenes" in the web browser and needs no engagement from the user's computer.


Types of DNS


An authoritative DNS service offers an optimization method for developers to handle their public DNS names. It then responds to DNS queries by converting domain names into IP addresses, allowing computers to communicate with one another. Authoritative DNS has final authority over a domain and is responsible for responding to recursive DNS servers with IP address information. 


Customers rarely query authoritative DNS services directly. Instead, they typically connect to a recursive DNS provider. A recursive DNS service functions equally to a hotel concierge: though it does not own any DNS records, it serves as an interface that can obtain DNS information on your behalf. If a recursive DNS caches or stores the DNS reference for some time, it responds to a DNS query by supplying the origin or IP details. If not, it forwards the query to one or even more credible DNS servers to gather the info.


What Steps are Involved in a DNS Lookup?


The domain name system is often associated with translating a domain name into the relevant IP address. To understand how this method operates, trace the route of a DNS lookup from an internet browser to the DNS lookup method and back again. Let us go over the steps.


Please remember that DNS lookup information is frequently cached, either locally on the querying workstation or remote location in the DNS infrastructure. A DNS lookup typically consists of eight steps. When DNS data is cached, steps in the DNS lookup procedure are skipped, making it faster. The following example shows all essential steps when no cache is present.


Step 1: OS Recursive Domain Name System Resolver Query


Because the os is unsure of the location of "www.example.com," it queries a DNS resolver. This same query sent by the OS to the DNS resolver includes a special flag that indicates it is a "recursive query." This implies that the resolver must finish the recursion and return either an IP address or an error.


Step 2: Iterative DNS Resolver Query to the Root Server


The resolver begins by requesting the IP address of "www.example.com" from any of the root DNS servers. Because this query lacks the recursive flag, it is an "iterative query," which means the reaction must be the location of an authoritative name server, an address, or an error. The hidden trailing "." at the end of the domain name represents the root. This extra "." is not required because your browser adds it automatically.


Step 3: Root Server Reaction


Top-level domains (TLDs) such as.com,.de,.io, and newer general-purpose TLDs such as cameras are hosted on these root servers.


The root does not have the IP address for "www.example.com," but it suspects that.com does, so it reverts the location of the .com servers. The root reacts with a list of the 13 NS or "name server" records for the .com gTLD servers.


Step 4: Iterative DNS Resolver Query to the TLD Server


The resolver then queries one of the .com name servers to locate the address of example.com. Each TLD, like the Root Servers, has 4-13 clustered name servers in various locations. TLDs are classified into country codes (ccTLDs) managed by government organizations and generic TLDs (gTLDs). Each gTLD has its own commercial entity in charge of running these servers. In this case, we will employ Verisign's gTLD servers, which manage the .com,.net,.edu, and.gov gTLDs.


Step 5: TLD Server Reaction


Each TLD server maintains a list of all the trusted name servers for every TLD domain. For example, each of the 13.com gTLD servers maintains a list of all the name servers for each and every.com domain. The .com gTLD server doesn't have example.com's IP addresses, but it does know where example.com's name servers are located. The .com gTLD server replies with a list of all NS records for example.com. The 'example' has 4 name servers in this case, from "ns1.example.com" to "ns4.example.com."


Step 6: Iterative DNS Resolver Query to example.com NS


Eventually, the DNS resolver looks up the IP address of "www.example.com" on one of the example's names servers.


Step 7: NS Response from example.com


This time, the queried name server is aware of the IP addresses and returns an AAAA or A address record (depending on the query type) for IPv6 and IPv4, respectively.


Step 8: DNS Resolver's Response to the Operating System


At this point, the resolver has completed the recursion procedure and can provide an IP address to the end user's OS.

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