What is DNS?
DNS is one of the most widely used protocols used in the Internet, which was introduced in 1984. As mentioned, to simplify the process of accessing the information of each site, a domain name was considered for each of them. Every website on the Internet has its unique domain and is known by it.
How does DNS work? Search methods
As mentioned, symbolic names on the Internet, organized into domains and subdomains, are not stored in a centralized file but distributed over the entire Internet network, so it may take several steps to translate a name into an IP address. Query” to find an address.
Typically, a query to convert a domain name is not always successful, and more questions may be required, or even a symbolic address may be wrong and have no equivalent IP address.
There are three ways to query name servers:
- Iterative Query (in English: Iterative Query)
- Recursive query (in English: Recursive Query)
- Reverse query (in English: Reverse Query)
Maybe this question is formed in your mind, how does DNS organize and identify domains?
The structure of this protocol is designed so that it is unnecessary to know all the registered domains. In simpler words, this protocol does not necessarily preserve territories but processes them and finally identifies them. For this purpose, the parts of websites follow a hierarchical structure. In this protocol, the details of the sites are checked step by step from right to left and finally identified.
The structure of each domain includes five main parts, which are:
- Root Domain
- Top Level Domain
- Second Level Domain
- Subdomain
- Host Name
DNS resource
DNS precursor is the first server programmed to receive requests from user systems through programs such as web browsers. Typically, the precursor is responsible for keeping users happy by responding to requests. This server is also called dns resolver.
This server can be considered the library manager who is requested to find a specific book somewhere in the library.
Root nameserver
This server is the first step in translating a human-readable domain name to an IP address. Of course, when the desired IP is not found in the DNS precursor. The job of this server is to refer the request to the server related to the extension related to the domain (.com, .ir, .org, etc.). This server can be considered a directory in a library, which refers to the different shelves of books.
TLD nameserver
TLD nameserver stands for Top Level Domain Server. This server is responsible for translating the domain extension and referring the rest of the domain name to the continuation server. This server can be considered a special shelf of books in the library.
SLD (Second Level Domain)
It is usually the name of the company or organization; after registering it, the network manager can register the addresses of his group.
Hosts
Within a domain, the domain owner can define hosts pointing to different computers or services through the main domain (example.com). Also, these different sections are accessible through the host definition, such as “www” (www.example.com).
Other definitions of the host also exist under the public domain. For example, you can provide access to a specific app through the API host (api.example.com), and you can also define a host called ftp or files (ftp.example.com or files.examples.com). Host names can be defined as any length as long as they are unique for each domain.
Subdomain
Subdomains are also a term related to the host. DNS works hierarchically. A TLD can have many domains under it. For example, both domains, google.com, and Ubuntu.com, are under TLD com. A subdomain refers to a domain that is part of a larger domain. In this case, we can say that Ubuntu.com is a com subdomain. Of course, this section is usually just called the domain (SLD), the domain of the second layer (Second Layer Domain).
Similarly, any domain can have subdomains under it. This second meaning is more common in the case of a subdomain. For example, your university can have a subdomain for each university department. For example, the history school can have a subdomain like “www.history.school.edu.”
A hostname and a subdomain are different because a host defines a computer or resource, while a subdomain extends a specific part of the domain. This is one of the methods of dividing the domain into smaller components.
Whether we call these parts subdomains or hosts, in any case, you will see that the leftmost parts of a domain are its more specific parts in order. This is how DNS works, i.e. , moving from right to left, parts of the domain name become more specific.
Authoritative nameserver
Authoritative nameserver performs the last lookup step. If the authoritative nameserver accesses the requested record, it returns the IP address for the requested hostname to the DNS precursor (responsible for the library) that issued the initial request. This server can be considered a dictionary in a bookshelf that can translate a specific name into a definition.
__________________________________________________________________________________________________________________________
Common three-letter domains include:
Com. The sites that use this domain are identified as economic and commercial institutions.
Edu. The owners of this domain are considered scientific or academic institutions.
Gov. This collection of domains is reserved for US government agencies.
Int. The owner of this domain is one of the international organizations (such as UNESCO, FAO,…).
Mil. This domain is used for military organizations around the world.
Net. The sites that use this domain are one of the network service providers.
Org. The owner of this domain is considered one of the non-profit organizations.
Each domain can be divided into smaller subdomains, which are also called second-level domains. For example, domains related to Iran, with the abbreviation ir. They are distinguished from other domains. For example, the names related to France are abbreviated as fr.
Faculty name: eng is an abbreviation for the technical engineering department
Domains are not the same as domains; a field can contain values related to multiple environments.
__________________________________________________________________________________________________________________________
Domain structure
The domain name consists of numbers and letters. One is the working name part, the other is the domain name, and the other is the subdomain.
For example, consider http://www.google.com.
http is the protocol for transferring information on the web. The // signs are used to separate the protocol from the domain. //:http is not part of the domain name system. The www part is the subdomain name. The Google part of the domain name and the .com part work. Each subdomain can have a different IP address than the domain name.
The domain name and subdomain are chosen and registered by the domain owner.
These parts include English letters and numbers, and the minus sign (-) can also be placed between numbers and letters (and nine at the beginning and end).
Various tools are approved and made available by Icann and contain 2 to 6 English letters.
Domain registration in many operators requires special permissions.
2-letter characters are provided to the countries that own them, and the governments determine the rules for registering them.
For example, the us is owned by America, and France owns fr.
__________________________________________________________________________________________________________________________
Advantages and disadvantages of DNS
Next, we will introduce the advantages and disadvantages of DNS.
What are the benefits of DNS?
According to the example of the phone book mentioned above, searching web pages would be very difficult if we kept all the necessary IP addresses to visit the desired sites. So perhaps the first and main advantage of DNS is to facilitate Internet use.
As mentioned, if you want to access a website, you must know its IP address. What if the IP address changes?
Another advantage of DNS is its up-to-dateness and stability. The DNS system is responsible for updating IP addresses very fast and consistently and making it easy for us to access websites.
What are the disadvantages of DNS?
No specific fault can be considered for dns. But if we want to discuss some DNS problems, we can mention the following.
One of these cases is DNS Attacks. In this case, the attacker replaces the site’s real address with a fake address to defraud or use SEO, and by deceiving the users of the attacked site, he directs them to malicious or intended addresses without their knowledge. Usually, this work aims to get bank information or other important and sensitive data of users and black hat SEO and gray hat SEO actions.
To get more information about this, you can read the article What is SEO and also the article What is a hacker and, of course, the interesting article Hacking the site.
What is a record?
DNS records contain essential information about a domain name. With the help of these records, DNS can provide access to a website or a web service.
Types of DNS records
dns in your database or database, you have records with different uses, which we will only introduce in Adame.
A Record
AAAA Record
CNAME Record
TXT Record
NS Record
SOA Record
MX Record
If you have any questions or experience with DNS, you can share them with us in the comments section.