What is a DNS Server
You may have heard of a DNS server when connected to the internet, which is an abbreviation for Domain Name System, but what is it?
Since the physical location of the device we are trying to connect to cannot be accessed by the site name hostname only, and all connections are made using IP addresses, we need a DNS service.
A DNS server is a device that connects the site name hostname to the IP address of the device to be accessed hosting that site. In this article, we will learn about the types of DNS servers, the types of DNS registrations, as well as the messages of the DNS service connection process.
It is a computer used by Internet Service Providers ISPs to search the database for the name of the site requested by the user. Then direct the user to the IP address associated with the name. And also plays an essential role in the functioning of the DNS service.
Also, DNS Resolver saves data in cache memory. For example, location example.com currently on the device that has the IP address 18.104.22.168 then all resolvers in the world will link the IP address as follows:
example.com <– 22.214.171.124
Therefore, if the server hosting the site changes and has an IP address 33.196.266.170. The memory for all resolvers in the world will remain with the old IP address for a period of time. This may cause the site to stop working for a period of time until the change spreads completely.
Data stored in the cache memory of DNS Resolvers are kept for a period of time called time to live TTL. This time can be set by registration settings when you purchase the domain for the site.
Types of DNS Servers
Central Root DNS Server
The central servers are the ones that have the addresses of all top Level Domain TLD server servers. The request first reaches the DNS central servers on its journey to obtain the IP address of the desired site name.
As of 2021, there are 13 servers around the world. This means that there are not only 13 devices around the world to deal with massive requests from around the globe, as there are several servers with local ISPs to respond to these requests.
Top-level Domain TLD Server
This type of server ranks relative to top-level domains such as .com Competent for companies and .org For non-profit organizations and the AU. Relative to the state of Australia (each country has its own domain) and others.
Typically, top-level servers form the destination of the request Messenger after the central DNS server and store a TLD-specific skin for the desired site name.
For example, if we ask for the IP address of the site in3case.com the request message will then go to the activity’s TLD servers .com then TLD servers send the trusted DNS server address of the trusted DNS server to the DNS Resolver.
Now our question appears: How do TLD servers know the authenticated server address? The answer is simply that when you buy the domain from companies like Godaddy, the company connects the domain to the TLD server so that it can connect with the Authoritative DNS Server.
Authoritative DNS Server
DNS Resolver sends Iterative queries to these servers at the end of the IP Address Search, as these servers store the real log Type, A, NS, etc, CNAME, TXT.
These servers return the IP address of the site name if it exists, but if it does not even exist in the Authoritative DNS server, it sends an error message, and the search for the IP address ends.
A, NS, CNAME, TXT are DNS record names, each of which is dedicated to a specific type of DNS request.
(A logs) are dedicated to connecting your IP address with the domain name.
While MX contains records of the address to which domain emails must be delivered Mail exchange record.
Types of DNS query messages
- The user sends these queries to the DNS Resolver, which are the first messages when any DNS lookup.
- The rapporteur can be your network admin, but most often it is your ISP.
Non Recursive Queries
- The address is located in the DNS Resolver decision.
- And it is answered immediately without sending any queries to other name servers.
This happens when the local DNS server has an IP address stored in its cache, or the query has arrived directly to the Authoritative name server which contains the required records, thus no need to send a Recursive query message.
- It occurs when the DNS Resolver cannot find the desired IP address, as it has not found the address in its cache memory.
- So, it sends a request to a central DNS server that knows how to find the desired TLD server.
Let’s discuss the steps:
1. The user sends a request to the DNS Resolver in the name of the site Hostname required its own IP address. This is a recursive query message.
2. DNS Resolver searches its cache memory to see if the address is already stored.
3. If the address exists, sends it directly to the user.
4. If it is not stored in its memory, the DNS Resolver decision sends an iterative request query message to the central DNS servers located around the world. (Until 2021 there was 13 central Root DNS server, whose names are from A to M).
5. The DNS Resolver then sends an iterative request query to the top-level domain server requesting the IP address of the domain. The TLD server answers with the authenticated server address of the desired domain.
6. Since the authenticated DNS server contains the records that connect the site name to its IP address. It sends the desired address to the DNS Resolver, which in turn returns the address to the user.
7 . If there is no corresponding record in the Authoritative server.
The error message “DNS_PROBE_FINISHED_NXDOMAIN” will appear indicating that there are no records of the name of the desired site.
8 . The address for the desired location name is stored in the cache memory of all servers where the request was made. So, when any user requests the same address the records will be in memory.
9 . In total, the process requires a maximum of four queries to do the DNS search, while the time taken is only a few milliseconds.
A suitable TLD for a Desired Domain
The central DNS server looks for a suitable top-level TLD for the desired domain. For example, if the name of the site in3case.com the appropriate TLD is .com. And the central server has access to the .com domain servers. The search result is thus sent to the resolver. The addresses of all servers must be central when scheduled otherwise the DNS request can fail.
The Concept of DNS Propagation
Suppose a website is hosted on the servers of a hosting company such as Digital Ocean. The server IP address is x. We want to change the server on which the site is located to another server. Let it have the address y, then we need to change the address in the Authoritative records. So, that DNS requests are sent to the new address.
Even if the records occur with the site hosting Authority, the process requires a period of time until the update is reflected in the memory of all the resolvers in the world where DNS propagation requires between 24-72 hours.
Fortunately, the process takes place even faster, with the majority of IP internet service providers assigning a low TTL lifetime.
In this post ” What is a DNS Server ” we covered many things like explaining what is a DNS. Also, types of DNS Servers, and types of DNS query messages. We talked about the whole process and the concept of DNS Propagation. I hope you find this article useful material.
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