Sudarshan S
3 min readMar 26, 2022

Are you online? Of course you are! And that’s how you are reading this blog right now. Would you like to know how this is possible? This series is all about what it takes to be online and access internet!

Hey peeps, in the previous blog of this series we have discussed about some of the most common application layer services and the servers that are used mostly in the application services. In this blog, we’ll be discussing about one of those type of servers, Domain Name System (DNS).

Domain Name Translation

The Domain Name Service is used to resolve the URL that we enter into their respective IP address. The reason why we use this Domain name translation is that it is impossible to remember all of the IP addresses for all of the servers hosting services on the internet. Instead, we can associate a name with an IP address, which is an easier way to locate servers.

The DNS provides a way for the hosts to request the IP address of a specific server. DNS names are registered and organized on the internet within specific high level groups, or domains. The most common high level domains are .com, .edu and .net, but there are many others. Some may denote a country code or geographic location, such as .us for United States or .ca for Canada.

DNS Servers

The DNS servers has a table that associates the hostnames in a domain with the corresponding IP addresses. The client uses the DNS server’s IP which is configured in the DNS settings of the host IP configuration. When a client has the name of the server, but needs to find the IP address, it sends a request to the DNS server on port 53. When the DNS server receives the requests, it checks the table to determine the IP address associated with that server.

If the local DNS server doesn’t have the entry for the requested name, it queries another DNS server within the domain. When the DNS server learns the IP address, then the information is sent back to the client. If the DNS server cannot resolve the IP address, then the request is timed and the client will not be able to communicate with the web server.

The domain name is usually contained in a URL. Domain name is made of multiple parts, called labels.

Types of DNS server

There are many server types involved in completing a DNS resolution. The following is the list of four name servers in the order a query passes through them.

  1. Recursive server: This server takes DNS queries from an application. It is he first access to the user which either provides the answer to the query if it has it cached, or accesses the next-level server if it doesn’t.
  2. Root name server: This is the next server that recursive server sends a query if it doesn’t have the answer cached. The root name server is an index of all the servers that will have the information being queried.
  3. TLD server: This server is called Top-level domain server. The root name server will direct the query based on the top-level domain like .com, .edu, .net in the URL. This is a more specific part of the lookup.
  4. Authoritative name server: This server is the final checkpoint for the DNS query. These know literally everything about a given domain and deal with the subdomain part of domain name. These servers contain DNS resource records with specific information about a domain. They return the necessary record to the recursive server to send back to the client.

Hope you learnt something new. In the upcoming blogs, we’ll be discussing about other types of servers.

Until then, Stay connected!!

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Sudarshan S

Tech enthusiast | Developer | Machine learning | Data science | Cybersecurity