The Domain Name System (DNS) is the Internet's equivalent of the Yellow Pages. You used to look up the business addresses you needed in the yellow pages back in the day. The DNA sequences are identical. You don't have to search it up because your computer is connected to the internet. So your computer knows where to go for Google, ESPN, and Varonis.com.
The protocol demands that two computers on an IP network have an IP address in order to communicate with one another. Consider an IP address to be similar to a street address: in order for one computer to "find" another, it must first know the other's number. Because most people recall names (e.g. www.classic.com) better than numbers (104.196.44.131), they require a tool that allows computers to convert names into IP addresses.
"DNS," or Domain Name System, is a program that converts names into numbers and vice
versa. We'd have to memorize the IP address of every server we wanted to connect to if DNS
didn't exist.
Consider DNS to be a phone book, but instead of connecting people's names to their addresses, it maps computer names to IP addresses. A "DNS record" is the name given to each link. Because there are so many computers connected to the Internet, storing all of the records in one large book is impractical. The DNS is instead divided into smaller books or domains. Because domains can be quite big, they are divided into smaller books called "zones." It would be impractical to store all of the books on a single DNS server. Instead, a large number of DNS servers keep all of the Internet's DNS records. Any computer may query its DNS server for a number or a name, and its DNS server understands how to query - and query - other DNS servers when it requires a record. An "upstream" query is when a DNS server queries other DNS servers. Queries for a domain can be directed "upstream" until they reach the domain's accountable server or the "authoritative name server." Administrators maintain server names and IP addresses for their domains on an authoritative name server. A DNS administrator makes a modification to their authoritative DNS server whenever they want to add, update, or delete a server name or IP address (sometimes called a "master DNS server"). There are other DNS servers that are known as "slaves." These DNS servers save copies of the DNS entries for your zones and domains.
The DNS Recursor is a server that responds to a DNS request by either asking another DNS server for the address or saving the website's IP address.
It responds to direct requests by returning a list of authoritative name servers for the top-level domain in question.
The top-level domain server (TLD) is one of the Internet's high-level DNS servers. A TLD server for ".com" answers first when you search for www.classic.com. The DNS then searches for "classic."
A DNS query's end station is the authoritative name server. The authoritative name server has the DNS entry for the request.
The DNS server that answers to the DNS query and looks for the authoritative name server or
a cached DNS result for the requested name is known as a recursive DNS resolver.
An authoritative DNS server saves the DNS request in its database. As a result, if you ask an
authoritative DNS server for one of its IP addresses, it won’t have to go to another server. For
these domains and IP addresses, the authoritative name server is the final authority.
What is DNS Caching and what are it’s Features?
The DNS cache acts as a database of domain names and IP addresses that is stored on a
computer. This prevents the computer from requesting the IP address each time. Imagine DNS
sending a request to the authoritative name server classic every time a user tries to call
www.classic.com. The traffic would be unbearable! Imagine the tremendous amount of traffic.
This is why DNS caching exists. DNS caching serves two purposes:
DNS queries should be processed faster.
DNS query bandwidth on the Internet is being reduced.
The DNS cache approach, on the other hand, has a few drawbacks:
Changes in the DNS take time to propagate, therefore it may take some time for every DNS
server to have the most recent IP data in its cache.
Hackers could use the DNS cache as an attack vector.
On the internet, there are several types of DNS caching:
Browser DNS caching: Current browsers with a development status of around 2018 have DNS
caching built-in. The DNS may be resolved quickly and efficiently using the local cache.
System software (OS) DNS caching: Your computer is a DNS client, and a service manages
DNS resolution and DNS queries on your computer. Its DNS cache is likewise local, making it
highly quick and consuming very little traffic.
DNS recursive resolution caching: Every recursive DNS server has a DNS cache, which stores
all known IP addresses for use in future requests.