DNS (Domain Name System) is a critical distributed computer system that serves as the backbone for obtaining information about domains. In simple terms, DNS is the technology that enables an internet browser to accurately locate a website using its domain name. In this comprehensive article, we will explore the complexity of DNS, from its server setup to its classification and configuration features. We will also take a look at how DNS is related to web hosting.
Let’s get started!
Understanding DNS Servers
Setting up a DNS server becomes much more manageable when you grasp its key features. Each website is physically located on a computer, and these computers communicate with each other on the network using IP addresses, conveniently converted from a digital format to an alphabetic one.
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Think of a DNS server as a phone book. Just like how you find a specific person’s number by their name in a phone book, the DNS system looks up IP addresses by domain names. It acts as a telephone directory, storing information about web resource names and their corresponding IP addresses.
In essence, DNS is a domain name system that facilitates the relationship between digital addresses and website names.
Basic DNS Records
DNS servers house various resource records, including:
SSHFP record: Stores snapshots of SSH keys in DNS.
AAAA record: Converts the hosting name into an IPV6 address.
TXT record: Represents textual information used for various purposes, such as indicating a host’s location.
SRV record: Functions to get the name of the service being searched for, along with its protocol.
CNAME record: Displays the alias as the canonical hostname.
NS record: Identifies DNS servers that are authoritative for a specific zone.
MX record: Identifies the email relay, the host that processes and forwards messages within the specified domain.
A-record: Converts the hosting name into an IP address.
Classification of DNS Servers
DNS servers can be categorized based on their primary functions:
Authoritative: Responsible for a specific zone.
Master servers (primary): Authorized to make changes to a zone (usually only one primary DNS server in a zone).
Secondary servers: Not permitted to make changes but receive notifications about changes made (unlimited number in one zone).
Caching: Responsible for user service, processing recursive requests, or forwarding them to higher-level servers (most servers interacting with users are caching servers).
Proxy servers (redirectors): Engage in caching but redirect information to a chain of caching servers associated with the redirecting server.
Root servers: Authoritative resources of root zones (only 13 worldwide).
Logging: Record data regarding user updates.
Recursive and Non-Recursive DNS
Recursion, in the context of DNS, refers to a request processing model where the DNS server conducts a complete search for data, including domains not delegated to the selected zone. Based on this criterion, queries can be classified as recursive or non-recursive.
Recursive requests involve the server polling all nodes in the sequence provided by decreasing zone levels until it receives a positive response or data that the domain in the search was not found.
Non-recursive requests, on the other hand, provide a positive response only if the request comes from a node within the server’s area of responsibility. Recursion may be absent due to specific types or prohibitions imposed by the DNS server.
What Does a DNS Zone Include?
The DNS zone encompasses various domains, meaning it contains data about network addresses where a domain is located. This information is stored in the form of a text file or lines in a database.
The DNS zone provides the following data:
A: Address of the Internet resource of the domain.
MX: Address of the mail server for the same domain.
CNAME: Synonymous value of the domain, redirecting to the Internet resource if the site name lacks the “www” format.
NS: Domains of DNS servers serving a specific domain.
TXT: Various text format notes.
How Does a DNS Server Work
The operation of a DNS server follows a simple principle with the following steps:
The user launches a web browser and enters the site’s name into the address bar, prompting the computer to send a request to the DNS server to retrieve the IP address of the domain.
If the requested data about the site is found in the cache, the request is sent to the root DNS server.
The root DNS server looks for information about the name servers of the hosting provider where the site is located, forwarding this information to the provider’s caching server.
The provider’s DNS server polls each of the name servers. If a positive result is obtained regarding the IP address, the data is cached to reduce the load on the channels and speed up results.
The provider’s DNS server then sends the IP address to the user’s browser that made the request.
Finally, the user’s browser is directed to the online resource after receiving the IP of the required website.
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