What is DNS?
DNS stands for Domain Name System. It is a system that translates domain names into IP addresses, which are numerical identifiers that computers use to communicate with each other over the internet.
Every website on the internet is identified by a unique domain name, such as google.com or facebook.com.
When you enter a domain name into your web browser, your computer sends a request to a DNS server to look up the IP address associated with that domain name.
The DNS server then returns the IP address to your computer, allowing your browser to connect to the website.
DNS is an essential component of the internet infrastructure and is responsible for directing internet traffic and ensuring that users can access websites and other online resources.
How does DNS work?
DNS works through a hierarchical system of domain name servers that store and distribute information about domain names and their corresponding IP addresses.
When you enter a domain name into your web browser, your computer sends a request to a DNS resolver, which is typically provided by your internet service provider (ISP).
The resolver checks its cache to see if it already has the IP address for the domain name. If it doesn't, the resolver sends a request to a root name server, which is the first step in the DNS hierarchy.
The root name server responds to the resolver with the IP address of a top-level domain (TLD) name server. TLDs are part of the domain name that comes after the final dot, such as .com, .org, or .net.
The resolver then sends a request to the TLD name server for the IP address of the next name server in the hierarchy.
This process continues recursively until the resolver reaches the name server responsible for the domain name that was originally requested.
The name server then returns the IP address to the resolver, which in turn provides it to your computer, allowing your web browser to connect to the website.
A brief history of DNS
The DNS (Domain Name System) was first introduced in the early 1980s as a way to simplify the way network addresses were managed and accessed on the Internet.
Prior to the DNS, network addresses were managed using a static hosts file on each individual computer, which had to be manually updated every time a new computer or network address was added to the system.
The first DNS specification was published in 1983 by Paul Mockapetris and Jon Postel, and the first implementation of DNS was released in 1984.
Initially, DNS was used primarily to map domain names to IP addresses, allowing users to access websites and other network resources using easy-to-remember domain names instead of complex IP addresses.
Over time, DNS has evolved to support additional features and capabilities, including support for different types of records (such as MX records for email servers and SRV records for service discovery), as well as more advanced security features such as DNSSEC (DNS Security Extensions).
Today, the DNS is a critical component of the Internet infrastructure, providing a distributed and decentralized system for resolving domain names to IP addresses.
DNS servers involved in a webpage loading
When you load a webpage, multiple DNS servers are involved in resolving the domain name to an IP address. Here are four examples of DNS servers that may be involved:
Recursive DNS server
This is the first DNS server that your device contacts when you request a domain name. It checks its cache to see if it already has the IP address for the domain name.
If it doesn't, it queries other DNS servers in the hierarchy to obtain the IP address.
Root name server
If the recursive DNS server doesn't have the IP address for the domain name, it will query one of the root name servers.
These servers are responsible for directing queries to the appropriate top-level domain (TLD) name servers.
TLD name server
The root name server responds to the recursive DNS server with the IP address of the TLD name server for the requested domain name.
The TLD name server is responsible for directing queries to the authoritative name server for the domain.
Authoritative name server
The authoritative name server is the final DNS server in the hierarchy that contains information about the IP address associated with the requested domain name.
It responds to the recursive DNS server with the IP address, which is then provided to your device to connect to the website.
These four DNS servers work together to quickly and efficiently resolve domain names to IP addresses, enabling you to access websites and other online resources.
Difference between an authoritative DNS server and a recursive DNS resolver
An authoritative DNS server and a recursive DNS resolver are two different types of DNS servers that play different roles in the DNS resolution process.
An authoritative DNS server is responsible for providing answers to DNS queries about a particular domain name.
It contains information about the IP addresses associated with the domain name and is considered the "source of truth" for that domain.
When a DNS resolver receives a query for a particular domain name, it will eventually contact the authoritative DNS server for that domain name to obtain the IP address.
On the other hand, a recursive DNS resolver is responsible for querying DNS servers on behalf of a client device to resolve a domain name to an IP address.
It receives a DNS query from a client device and then recursively queries other DNS servers to obtain the IP address for the domain name.
The resolver caches the results of its queries to speed up future DNS resolutions for the same domain name.
The main difference between an authoritative DNS server and a recursive DNS resolver is that an authoritative DNS server provides answers to DNS queries about a specific domain name, while a recursive DNS resolver queries other DNS servers on behalf of a client device to resolve a domain name to an IP address.
Difference between DNS resolver, DNS server, and DNS lookup
DNS resolver, DNS server, and DNS lookup are all related to the Domain Name System (DNS), which is responsible for translating domain names into IP addresses.
However, they refer to different components and functions within the DNS system.
A DNS resolver is a software component or service that resides on a client device, such as a computer or smartphone and is responsible for sending DNS queries to a DNS server.
A DNS server, on the other hand, is a computer or network device that stores DNS records and responds to queries from DNS resolvers.
When a DNS resolver sends a query to a DNS server, the server looks up the requested domain name in its database and returns the corresponding IP address to the resolver.
DNS lookup, also known as a DNS query, is the process of requesting information from a DNS server about a specific domain name.
This process involves sending a DNS query to a DNS resolver, which then sends the query to a DNS server. The DNS server searches its database for the requested domain name and returns the associated IP address to the resolver.
What are the steps in a DNS lookup?
Here are the steps involved in a DNS lookup:
The user enters a domain name into their web browser.
The computer sends a DNS query to a DNS resolver, which is typically provided by the user's internet service provider (ISP).
The DNS resolver checks its cache to see if it already has the IP address for the domain name. If it does, it returns the IP address to the computer.
If the DNS resolver doesn't have the IP address in its cache, it sends a DNS query to a root name server.
The root name server responds to the DNS resolver with the IP address of a top-level domain (TLD) name server.
The DNS resolver sends a query to the TLD name server for the IP address of the next name server in the hierarchy.
This process continues recursively until the DNS resolver reaches the authoritative name server for the domain name.
The authoritative name server responds to the DNS resolver with the IP address for the domain name.
The DNS resolver caches the IP address and returns it to the computer.
The computer uses the IP address to connect to the server hosting the website associated with the domain name.
These steps ensure that the computer can locate the correct IP address associated with a domain name, allowing it to connect to the website.
DNS lookups happen quickly and efficiently, enabling users to access websites and other online resources.
What are the types of DNS queries?
There are several types of DNS queries that can be made by a client device to obtain information about a domain name. Here are some of the most common types:
A records query - This type of query is used to obtain the IP address associated with a domain name.
MX records query - It is used to obtain information about the mail server associated with a domain name.
CNAME records query - This type of query is used to obtain information about the canonical name associated with a domain name.
NS records query - It is used to obtain information about the authoritative name servers for a domain.
SOA records query - This type of query is used to obtain information about the start of authority (SOA) record for a domain.
PTR records query - This query is used to obtain the domain name associated with a particular IP address.
What is DNS caching?
DNS caching is a mechanism used to temporarily store DNS query results in memory, allowing for faster resolution of subsequent DNS queries for the same domain name.
When a DNS resolver receives a DNS query, it first checks its cache to see if it already has the IP address for the domain name.
If it does, it returns the IP address to the client device without having to query other DNS servers in the hierarchy.
DNS caching works by storing the results of previous DNS queries in memory for a specified period of time, known as the time-to-live (TTL).
The TTL is set by the authoritative name server for the domain name and specifies how long the DNS resolver should cache the query result before it expires.
Caching is essential for DNS performance, as it reduces the time it takes to resolve DNS queries and minimizes the load on DNS servers in the hierarchy.
It also helps to ensure the availability of DNS information even if some of the DNS servers in the hierarchy are temporarily unavailable.
However, DNS caching can also cause problems if the cached information is out of date or incorrect.
In some cases, changes to DNS records can take time to propagate through the DNS system, and cached information can continue to be used even after it has become stale.
This can result in users being directed to the wrong IP address or experiencing other DNS-related issues.
Where does DNS caching occur?
DNS caching can occur at several different levels in the DNS resolution process:
Local device cache
Client devices such as computers and smartphones often have their own DNS cache, which stores the results of recent DNS queries.
This allows the device to quickly retrieve the IP address associated with a domain name without having to send a new query to a DNS resolver.
Recursive DNS resolver cache
DNS resolvers provided by ISPs or other organizations typically have their own cache to store the results of recent DNS queries.
This allows the resolver to quickly retrieve the IP address associated with a domain name without having to query other DNS servers in the hierarchy.
Authoritative name server cache
Authoritative name servers for a domain may also cache DNS query results to improve performance and reduce the load on their servers.
When an authoritative name server receives a DNS query, it checks its cache to see if it already has the IP address for the domain name.
Intermediate DNS caches
In addition to the above, intermediate DNS caches may also exist between the recursive DNS resolver and the authoritative name server.
These caches may be operated by ISPs or other organizations and are used to improve DNS performance by reducing the number of DNS queries that need to be sent to authoritative name servers.
DNS caching at each of these levels can help to improve DNS performance and reduce the load on DNS servers.
However, it is important to ensure that cached information is accurate and up-to-date, as outdated or incorrect information can lead to DNS-related issues.
Is DNS secure?
The DNS is generally considered to be secure, but it is also vulnerable to various types of attacks that can compromise the security and integrity of the system.
One of the main security issues with DNS is DNS spoofing or cache poisoning, which involves an attacker sending false DNS information to a DNS resolver, causing it to return incorrect information to clients.
This can lead to users being directed to fake websites or other malicious resources.
Another security issue with DNS is DNS hijacking, which involves an attacker taking control of a domain name by modifying the DNS records associated with it.
This can allow the attacker to redirect traffic intended for the legitimate domain to their own malicious servers.
To mitigate these and other security threats, various security mechanisms have been developed for DNS, including DNSSEC (DNS Security Extensions), which provides cryptographic validation of DNS responses to prevent spoofing and other attacks.
In addition to DNSSEC, other security measures for DNS include the use of firewalls, intrusion detection and prevention systems, and secure protocols such as DNS over HTTPS (DoH) and DNS over TLS (DoT) to encrypt DNS queries and responses and protect them from interception and manipulation.
Overall, while DNS is not immune to security threats, there are many tools and techniques available to help ensure the security and integrity of the system, and ongoing efforts are being made to improve DNS security and resilience in the face of evolving threats.
How to find my DNS server?
There are several ways to find out which DNS server your device is currently using:
Check your network settings: On a Windows computer, you can check your DNS server settings by going to Control Panel > Network and Sharing Center > Change adapter settings > Properties > Internet Protocol Version 4 (TCP/IPv4) > Properties.
On a Mac, go to System Preferences > Network > Advanced > DNS. Your DNS server address should be listed in these settings.
Use command prompt or terminal: On a Windows computer, you can use the command prompt to view your DNS server address by running the command "ipconfig /all". On a Mac, you can use the terminal and type the command "scutil --dns". This will display the DNS server address currently being used.
Use online tools: There are several websites that can help you determine your DNS server, such as DNS Checker and What's My DNS Server.
It's important to note that your DNS server may be automatically assigned by your internet service provider (ISP), or you may have manually configured it to use a specific DNS server.
If you're experiencing issues with your current DNS server, you may want to consider changing it to a different server that may provide better performance or security.
Does DNS service affect SEO and how?
DNS itself does not directly affect SEO, but issues with DNS can indirectly impact SEO by affecting website accessibility and performance.
If a website's DNS is not properly configured, it can cause slow page load times, site downtime, and other issues that can negatively impact user experience.
These issues can cause search engines to rank the site lower in search results, as they prioritize sites that provide a good user experience.
In addition, DNS-related issues such as DNS hijacking or DNS spoofing can lead to a website being flagged as insecure or untrustworthy, which can negatively impact its reputation and SEO rankings.
To ensure that DNS-related issues do not negatively impact SEO, it's important to properly configure DNS settings, regularly monitor DNS performance and security, and quickly address any issues that arise.
This can help ensure that a website is accessible, secure, and performs well, which can ultimately improve its SEO rankings.