Domain Name System – DNS

DNS or a Domain Name System is an amazing technology. You can see DNS as a hierarchy system of domains/hostnames and IP addresses. It helps us open internet addresses without a hustle. We easily write the domain name and the DNS has the job to find the IP of the domain we wrote. Just like the phone book on your mobile phone, you need to find Mike, so you write “Mike”, and you don’t need to remember his actual number, great isn’t it?

DNS is an essential part of the Internet. It manages to translate all the inquiries into IP addresses, and like this, it can identify different devices that are connected to the network.

Apart from translating hostnames to IP addresses (A and AAAA DNS records), DNS also has many different functions like defining port in use, connecting services to domains, authentication of emails, and many more. There are 50+ types of DNS records with different functionality.

Why do we need the Domain Name System (DNS), and why is it important?

The Domain Name System is a fundamental component of the Internet infrastructure, playing an essential role in ensuring the smooth operation of online services and communication. DNS serves for:

• Matching hostnames to IP addresses: DNS allows users to access websites using memorable domain names instead of complex IP addresses, improving usability and accessibility.
• Pointing services: It enables organizations to map domain names to specific services, such as web servers, email servers, FTP servers and more.
• Directing messages to mail services: DNS also plays a crucial role in email delivery by mapping mail server addresses (MX records) to domain names. This ensures that emails are routed correctly to their intended recipients.
• Authentication and validation of emails and different services: It supports various protocols, such as SPF, DKIM, and DMARC, which authenticate and validate email senders and prevent spam and phishing attacks.
• Creating VPN: DNS can be used to set up Virtual Private Networks (VPNs) by resolving domain names to internal IP addresses and ensuring secure remote access to corporate resources.
• Creating a Content Delivery Network: DNS powers Content Delivery Networks (CDNs) by routing requests to geographically distributed servers, optimizing content delivery and enhancing user experience.
• Load balancing: DNS-based load balancing distributes traffic across multiple servers, improving scalability, resilience, and performance.
• Increase your uptime: Effective DNS management strategies, such as redundant server setups and optimized configurations, contribute to increased uptime.

DNS history

Before the Internet, there were different networks like ARPANET, SATNET, and many packet radio ones. The problem was that there was not a single united network. There was a need to solve this problem, and the solution was the Domain Name System (DNS). 

The person who got the task to create it was Paul Mockapetris. His team needed to find a way to have IP addresses and hostnames aligned. 

A centralized file called HOSTS.TXT matched the first existing sites to IP addresses, but this was not a solution that could handle millions of sites.

After several years of work, in 1983, the DNS was created and joined the Internet Standards of Internet Engineering Task Force in 1986. The founding documents of it were RFC 1034 and the second RFC 1035. There you can find information about the protocol, its functionality, and data types. 

A later update of DNS allowed dynamic zone transfers (IXFR) and the use of NOTIFY. The NOTIFY mechanism gave the Primary DNS servers the power to “notify” the Secondary about the changes in the DNS records. 

Now the Secondary DNS servers could update when a change occurs in the Primary and get only the change.  

And another critical moment was the creation of the DNSSEC and its version from 1999 (RFC 2535). It is a security layer that defends the DNS from poison attacks. 

Here you can read more about the History of DNS.

Components of DNS. What does DNS include?

The Domain Name System has several essential components, each playing a crucial role in its operation:

• Domain namespace. It is a tree-like hierarchy structure that divides hostnames into smaller pieces called domains. They are further divided into more categories: top-level domains, second-level domains, and subdomains. 
• DNS servers. These servers handle the resolution of domain names to IP addresses. They include authoritative servers with the original DNS records, recursive servers that cache and resolve queries, root name servers that direct queries to TLD servers, and TLD servers that manage second-level domains.
• DNS query. Each request comes from a device that demands a DNS record. It is a question that runs from one recursive server to another in search of the answer. 
• DNS records. Domain name system keeps information in so-called DNS records. They are text documents with various purposes like A Record, SPF record, CNAME record, etc. 

DNS server types

DNS servers play different roles in the process of resolving domain names. Here are the primary types of DNS servers:

• Recursive DNS servers: These servers handle queries from clients and perform the necessary lookups to resolve domain names into IP addresses. They can cache results to speed up future queries.
• Root Name servers: Root servers are at the top of the DNS hierarchy. They respond to queries for records in the root zone and direct them to the appropriate Top-Level Domain (TLD) servers.
• TLD Name servers: These servers manage the DNS records for domains under a specific top-level domain, such as .com, .org, or .net. They direct queries to the authoritative servers for the requested domain.
• Authoritative DNS servers: These servers store the DNS records for a domain. They provide answers to queries about domains they are responsible for, delivering the most accurate information.

How does the Domain Name System work? Example:

Let’s explain a little bit more about how DNS actually works. The process has the following steps:

1. Information request
You want to visit our website and you know the domain name. You write it in your browser, and the first thing it does is to check for local cache if you have visited it before, if not it will do a DNS query to find the answer.

2. Recursive DNS servers
If you haven’t visited the page before, your computer will search the answer with your internet provider’s recursive DNS servers. They have cache too so you can get the result from there. If they don’t, they will need to search the information for you in another place.

3. Root name servers
Your query can travel a long way. The next step is the name servers. They are like intermediates; they don’t know the answer, but they know where to find it.

4. Top-Level Domain (TLD) name servers
The name servers will read from right to left and direct you to the Top Top-Level Domain (TLD) name servers for the extension (.com or another). These TLD servers will lead you finally to the servers which have the right information.

5. Authoritative DNS servers
These DNS servers check the DNS records for the information. There are different records, for example, we want to know the IP address for a website, so our request is Address Record (A).

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6. Retrieve the record
The recursive server gets the A record for the website we want from the authoritative name servers and stores it on its local cache. If somebody else needs the host record for the same site, the information will be already there, and it won’t need to pass through all these steps. All this data has an expiration date. This way, the users will get up to date information.

7. The final answer
Now that the recursive server has the A record it sends it to your computer. The PC will save the record, read the IP and pass the information to your browser. The browser makes the connection to the web server, and it is finally possible for you to see the website.

Commonly used DNS records

The DNS records represent instructions and information about a specific domain name. A DNS query is initiated to find such information, and a different DNS record could be pursued depending on the user, query, or application.  

There are a lot of different DNS record types, and each of them serves a precise purpose. Here are some of the most commonly used DNS records:

• SOA record – The SOA stands for Start Of Authority. It is one of the fundamental DNS records which describes the origin of the authoritative DNS zone. Additionally, it holds important details about the zone, including information about the primary name server, the domain administrator’s email address, the domain serial number, and details regarding zone transfers.
• A record – The A simply means address. This record contains the IP address of a domain. It is important to mention that A records are responsible for IPv4 addresses. In case you need a record for your IPv6 address, then you should use the AAAA record instead. In most cases, websites have a single A record. However, some sites are more significant and hold more than one. That is very beneficial for load balancing and handling heavy traffic.
• NS record – This is another fundamental DNS record that indicates which is the responsible authoritative server for keeping all related data for a particular domain. There are cases when domains have primary and secondary (backup) name servers for better reliability, then multiple NS records are required for directing DNS queries to them.
• CNAME record – A Canonical Name record is a very helpful type of DNS record that points one hostname to another hostname. It is typically utilized to direct a subdomain, like www, or mail to the domain. Yet, you should be careful because it can’t coexist with other DNS records.
• TXT record – This record allows the DNS administrator to include text instructions related to their domain name. TXT records are commonly used for verifying domain ownership, securing your emails, and protecting against email spam.
• SPF record – The Sender Policy Framework record is a TXT DNS record type that specifies which servers have permission to send emails on your domain’s behalf. It is crucial if you want to stop criminals from spoofing your domain.

How does the Domain Name System affects the web performance?

Recursive DNS servers are able to store the DNS data (like A records and IP addresses) received from DNS queries in their DNS cache for a limited amount of time. That way, the servers are capable of providing quick replies if requests for the same IP address appear. For that reason, caching DNS information is very efficient.

When multiple users request to access the same website, the local DNS server would have to complete the entire DNS resolution process just once. Afterward, it will answer the rest of the requests with the information in its DNS cache.

As we mentioned, the DNS data is available only for a specific amount of time, determined by the TTL (Time-To-Live) value. Administrators have the responsibility to set it, and it could be different depending on their preferences. Longer TTL helps decrease the load on the Authoritative DNS servers. On the other hand, shorter TTL will guarantee more accurate answers.

Suggested article: What web performance monitoring is?

DNS server not responding? How to fix it?

When you encounter the message “DNS Server Not Responding,” it means your device is unable to contact the DNS server to resolve the domain name you are trying to access. This issue can arise from various causes:

• Network Connectivity Issues: There might be problems with your internet connection or the network you are using.
• DNS Server Problems: The DNS server you are trying to reach may be down or experiencing high traffic, making it unresponsive.
• Incorrect DNS Settings: Your device’s DNS settings might be configured incorrectly, preventing it from communicating with the DNS server.
• Firewall or Security Software: Sometimes, firewall or security software on your device can block DNS traffic.

To resolve this issue, try these troubleshooting steps: switch to a different browser or device to see if the problem persists, check your network connection and restart your router, temporarily disable your antivirus software and firewall, and ensure no conflicting secondary connections or peer-to-peer features are active. Additionally, update your network adapter drivers, flush your DNS cache using Command Prompt, and consider changing your DNS server settings to a reliable service. Disabling IPv6 in your network settings may also help.

DNS SECURITY

Over time, cybercriminals found vulnerabilities in the Domain Name System (DNS) and managed to use them to their own advantage. The most common threat is called DNS spoofing (DNS poisoning), where falsified data is distributed to the Recursive DNS servers. Usually, the false information directs user requests to a source pretending to be the Authoritative DNS server. So, as a result, the requests are typically directed to a fake website. 

Criminals use tricky titles and aim to convince users that the website is genuine, so they can gain access to the user’s personal details. Sometimes, for instance, they substitute a character in the domain name with a similar-looking character, like replacing the letter l with the number 1. If the user doesn’t notice the difference, the risk of becoming a victim of a phishing attack is relatively high.

The best option for boosting your DNS security and minimizing the risk of becoming a victim of DNS spoofing (DNS poisoning) is to implement DNSSEC (DNS Security Extensions). With it, the DNS data (DNS records) is signed cryptographically. That way, its integrity and authenticity are guaranteed. Other security measures for mitigating such threats are DNS-over-HTTPS (DoH) and DNS-over-TLS (DoT), which encrypt DNS queries and responses, protecting them from eavesdropping and tampering.

Conclusion

The Domain Name System is a fundamental pillar of the Internet, enabling seamless access to websites and services by translating human-readable domain names into IP addresses. It is a long process, but actually, it takes fractions of a second. It can be even faster if you use reliable DNS servers from ClouDNS. Check our DNS services and choose the one that best suits you. With continuous advancements and robust security measures like DNSSEC, DNS remains a reliable and secure backbone of the Internet. For businesses and individuals alike, understanding and optimizing DNS can lead to improved web performance, enhanced security, and a better overall user experience.

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Authoritative DNS server

Such a server is the name server, which has the original zone records. It has been configured from the original source, and it returns answers to queries that have been predetermined by the administrator.
These DNS servers are giving responses to queries just for the zones they are configured. This makes them very efficient and fast. They will not respond to recursive queries too. The requests that reach them are from Resolving name servers (resolvers) and the authoritative servers will either have the complete answer or they will pass to the name server who is responsible for it.

The authoritative servers don’t cache query results. They have data that is saved in their system.
It can be master or slave. It can store the original zone records, or a secondary server which communicates directly with the primary and copies the records directly through a DNS mechanism.

The authoritative DNS servers can be where the website is hosted or where the DNS provider is.

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Types of Authoritative name servers

An Authoritative server provides definitive answers to DNS queries, such as mail server IP address or web site IP address (A resource record). It does not simply return cached responses from another name server, but rather provides answers to queries about domain names that are configured in its system. We distinguish two types of Authoritative DNS servers: Primary name servers and Secondary name servers.

• A Primary name server (also known as a Master server) stores the authoritative copies of all zone records. The DNS administrator is responsible for making changes to Master server zone records. All Slave Servers receive updates via the DNS protocol’s special automatic updating mechanism and maintain an identical copy of the Master records.
• A Secondary name server (also known as a Slave server) is an exact replica of a Master server. We use it to distribute the load on the DNS server and to increase the availability of a DNS zone in the event of a failure (DNS outage, DNS attacks, etc) of the Primary server. Furthermore, it is advisable for a domain to have at least two Slave servers and one Master server.

Authoritative DNS server vs. Recursive DNS server 

Both Authoritative DNS servers and Recursive DNS servers have crucial functions, and they depend on each other to fulfill their purposes. However, there are some fundamental differences between them. 

Authoritative DNS servers store the most recent and accurate information (DNS records) for a domain and are able to provide the final answers for users’ DNS queries (DNS lookups). On the other hand, Recursive DNS servers only keep a copy of the DNS information for a particular amount of time, also known as Time to live (TTL). Additionally, they often have to obtain the answer for a DNS query from another server. 

So let’s explain a little bit more about the differences between them!

Аuthoritative DNS server

An Аuthoritative DNS server is responsible for answering DNS queries for a particular set of DNS zones by providing information from its own data. It does not have the need to reference another source. Most commonly, it replies to the requests with one of the following types of answers:

• Authoritative DNS information (DNS records) from its own store. It could come from a master zone file, from a secondary zone duplicate transferred from a master server, from Dynamic DNS, etc.
• In case it doesn’t know the answer, it is going to direct to another nameserver. For instance, the Root name server points to the responsible TLD (Top-Level Domain) server.
• An authoritative NXDOMAIN. It replies that the requested domain name doesn’t exist.
• An authoritative empty NOERROR (NODATA) answer. The requested domain name exists, but the particular queried DNS record does not.

Recursive DNS server

The Recursive DNS server replies to DNS queries by asking other nameservers for the needed information (DNS records). In some cases, this server responds to DNS requests directly from its cache if the information is available there. In case it is not, the Recursive DNS server, also known as DNS resolver, is going to perform a search and ask the responsible authoritative servers until it finds the needed answer.

Normally, Recursive DNS servers store in their cache memory information about previously queried domain names for further use. That really reduces the network traffic and improves the performance. 

Recursive DNS servers normally answer DNS queries in the following way:

• Authoritative DNS information (DNS records) from its own store, if there is any. That could be a positive response, NXDOMAIN, or NOERROR/NODATA.
• Non-authoritative DNS information that is received and cached from a previous recursive DNS query, if there is any.
• Data retrieved from remote authoritative name servers. It can be further cached and reused for answering future DNS queries.

Recursive DNS servers are most commonly used to reply to general DNS queries for users on a local network.

How to get Authoritative DNS server for a domain?

It is actually very easy to get the Authoritative DNS server for a domain name. Here we are going to show you how by using popular tools such as Dig, NSlookup, Host, and WHOIS. 

• Dig command

We are going to use the Dig command and request the NS records, where NS stands for nameserver. Therefore, this DNS record is going to show us which are the authoritative DNS servers for the particular domain name or DNS zone.

Type the following:

$ dig +short NS exampledomain.com

• NSlookup command

NSlookup is another popular tool that can help you get the Authoritative DNS server for a domain name or a DNS zone. It works on Windows, Linux, and macOS. Once again, we are going to query the NS records.

Simply type the following:

$ nslookup -type=NS exampledomain.com

• Host command

Host command is a beneficial tool that you can use on your Linux or macOS device. For our purpose, to get a list of the Authoritative DNS servers, we should request the NS record. 

Just write the following:

$ host -t NS exampledomain.com

• WHOIS 

With the WHOIS command, you can get a list of the Authoritative DNS servers too. 

Write the following:

$ whois exampledomain.com | grep -i “Name .*:”

*Make sure to replace “exampledomain.com” with the one you want to check.

Importance of Authoritative DNS Servers

Authoritative DNS servers are critical for several reasons:

• Resolution: Authoritative DNS servers translate domain names into IP addresses, enabling users to access websites and services.
• Accuracy and Reliability: They maintain up-to-date records, ensuring users receive correct IP addresses for requested domains.
• Performance: By distributing authoritative DNS servers globally, organizations can reduce latency and improve the performance of DNS resolution.
• Security: Properly configured authoritative DNS servers play a crucial role in mitigating DNS-related attacks, such as DNS spoofing and DDoS attacks.
• Domain Management: They give administrators the possibility to modify DNS records and make the needed adjustments to effectively direct traffic.

Best Practices 

For optimal performance and security, it is best for organizations to stick with the best practices when managing authoritative DNS servers:

• Redundancy: Deploy redundant authoritative DNS servers across multiple geographic locations to improve fault tolerance and minimize downtime.
• Security Measures: Implement security measures such as DNSSEC (Domain Name System Security Extensions) to protect against DNS-related threats.
• Regular Monitoring: Monitor authoritative DNS servers regularly for performance issues, unauthorized changes, and potential security breaches.
• Capacity Planning: Predict future growth and ensure that servers can handle increased DNS query loads without degradation in performance.

Conclusion

So now you are familiar with what the Authoritative DNS server actually is and its crucial purpose! Its ability to provide authoritative answers to the DNS requests (DNS queries) is one of the key fundamentals of the entire DNS (Domain Name System) and the Internet as well! 

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DNS explanation

To understand clearly how DNS filtering operates, we need to explain the purpose of the Domain Name System briefly. 

DNS, which stands for “Domain Name System,” converts the names of websites into IP addresses that browsers can recognize. As a result, whenever you visit a website, your browser requests a particular kind of DNS server. This server returns a corresponding IP address after examining the requested domain name. Then, the page can be loaded from there in a split second, providing you full access.

What is DNS filtering?

DNS filtering, or DNS blocking, is a security technique that prevents access to malicious, untrustworthy, or otherwise undesirable domains or IP addresses. When a user attempts to access a web address, the DNS query is compared to a blocklist of undesirable domains or IP addresses. And if a match is found, the domain is not resolved, and access is denied.

How does it work?

It works in a simple way. All DNS queries are routed through a Recursive DNS server (DNS resolver). DNS resolvers that have been specially configured can also act as filters by refusing to resolve queries for specific domains that are tracked in a blocklist, preventing users from accessing those domains. DNS filtering services can also employ an allowlist rather than a blocklist

Let’s say an employee for the organization receives a phishing email. It falls for the trick of clicking a link that takes them to malisiousexample.com. The company’s DNS resolving service, which uses DNS filtering, receives a query from the employee’s computer before it loads the webpage. The DNS resolver will reject the request if the malicious website is listed on the company’s blocklist. This will stop maliciousexample.com from loading and stop the phishing attack.

DNS filtering can ban websites either by IP address or domain name:

• By IP address: The DNS resolver tries to resolve every domain, but the resolver won’t send the result back if the querying device’s IP address is on the blocklist.
• By domain: For some domains, the DNS resolver does not even attempt to resolve, or look up, the IP addresses.

What does having a secure DNS server mean?

A secure DNS server is a DNS resolver that filters unsafe or restricted webpages as part of a DNS filtering service. Some secure DNS servers also offer enhanced privacy to protect user data, such as Private DNS servers, which delete all DNS query records after some time.

Since DNS was not intended with security in mind from the start, there are additional techniques to make the DNS process safer besides DNS filtering. For example, the DNSSEC ensures that DNS resolvers provide accurate information and are not compromised. In addition, DNS over TLS (DoT) and DNS over HTTPS (DoH) encrypt DNS queries and responses, making it difficult for attackers to track a user’s DNS requests.

Why should you filter DNS?

Due to its adaptability, DNS filtering provides customers with advanced customization options. You can select which content types are allowed and which should be blocked based on the requirements of your organization. In addition, you protect your users from harmful content by implementing DNS-based web blocking. In addition, DNS filtering provides additional benefits, such as: 

• Stops visitors from visiting dangerous or harmful websites.
• Includes simple category-based filtering, blacklisting and whitelisting.
• It prevents visitors from going to phishing websites.
• Stops the download of potentially illegal files.
• Make browsing safe and secure for network users, Wi-Fi users, and visitors.
• Restricts malware downloads for users

What types of DNS attacks can target me if I don’t have DNS filtering?

• DNS cache poisoning (DNS spoofing): The goal of this attack is to taint the recursive servers, specifically the cached replies. If they are successful, any following query will receive a poisoned response.
• DNS hijacking: This attack aims to send DNS messages to a different domain name server with completely bogus information to redirect users to dangerous web pages. Because it is sent to a different location, malware on the target client PC might enable all DNS requests to be routed to the attacker’s controllable DNS server.
• DNS tunneling: It drills into DNS messaging and passes malware using SSH, TCP, or HTTP. DNS tunneling entails encoding communications in DNS queries and responses. This DNS attack leaks sensitive information, in which case the constantly changing domain names make it very challenging to catch.

DNS filtering vs Web filtering

There are two different kinds of content filtering: DNS filtering and web filtering. DNS filtering restricts website access based on DNS queries. On the other hand, web filtering prevents access to specific websites based on their URL. As DNS filtering can prevent access to websites even before they are loaded, it is often more effective than web filtering.

In general, web filters are less precise than DNS filters. This is because DNS queries are frequently more accurate than URLs. For instance, a DNS query for “example.com” will always result in the same IP address. But, depending on your region, the example.com URL can change. Whether you are logged in, or not can also affect how it changes.

Web filtering typically takes longer than DNS filtering. This is because DNS queries often resolve more quickly than URLs. DNS filtering might also obstruct access to websites using secure connections (HTTPS).

Comparison DNS filtering with other security measures

DNS filtering is a vital security layer, but it’s important to understand how it compares with other measures:

• Firewalls: Firewalls control incoming and outgoing network traffic based on predefined security rules. While DNS filter blocks access to harmful domains, firewalls regulate data packets based on source, destination, and types of traffic, offering a different layer of security.
• Antivirus Software: Antivirus programs detect, prevent, and remove malware. DNS filter complements this by preventing access to malicious sites where malware can be downloaded, thus reducing the antivirus software’s load.
• Email Filtering: This specifically targets email threats like phishing and spam. DNS filtering adds an extra layer of security by blocking access to malicious links that might be missed by email filters.
• Endpoint Protection: Endpoint protection focuses on securing endpoints in a network. While this is crucial for detecting and responding to attacks, Domain Name System filtering prevents threats at the network level before they reach endpoints.

Can DNS filtering be bypassed?

While DNS filtering is a powerful way of safeguarding against online threats, it is not infallible. Skilled individuals can bypass DNS filters using various methods such as Virtual Private Networks (VPNs), proxy servers, or by changing the DNS settings on their devices. These methods allow users to avoid the restrictions set by DNS filtering by routing their internet traffic through different servers. To counteract this, it’s important for organizations to employ a comprehensive security strategy that includes regular updates and additional protective measures alongside DNS filtering, DDoS Protection, DNSSEC, Private DNS servers, etc. These approaches ensure a robust defence against evolving cyber threats, maintaining the integrity of network security.

Conclusion

DNS filtering is essential for organizations that want to keep their networks and users safe, whether working in a public Wi-Fi environment or within their corporate network. It provides granular customization options to tailor user access policies, block unwanted content, and enhance privacy. With the constant threat of DNS-based attacks on the rise, implementing a reliable DNS filtering service is the key to ensuring a secure connection for all users.

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Recursive DNS server explained

The Recursive DNS server called, also commonly DNS resolver, has the important responsibility of seeking requested data and responding to users’ DNS queries.

In computing, when we talk about recursion, it is clearly associated with a technique that aims to solve a particular problem. In addition, that involves a program or solution that continuously repeats itself until it reaches the desired goal.

A Recursive DNS server is positioned to function in the middle between the Authoritative DNS server and the end-users that initiate DNS requests. So, each time a user desires to visit and explore a particular website, it types its domain name into the address bar of the browser. From there, the Recursive DNS server receives the request and starts searching for the IP address (IPv4 or IPv6) that corresponds to the domain name. Shortly after the required IP address is found, the DNS resolver returns to the user’s device and provides the needed information. Then the browser on the device (smartphone, laptop, computer, etc.) of the user is able to connect and load the desired website. 

The number of available Recursive DNS servers all over the world is significant. However, the most popular among them are the ones of the Internet service providers (ISP).

Tasks of the Recursive DNS server

The role of the DNS resolver is to complete one of the following tasks:

1. Checks if the IP address is stored in the cache memory. There is a certain period of time, pre-defined by the domain’s owner called Time to Live or TTL. It says for how long the Recursive server can hold the information. If it is still there, it will return the answer fast and won’t take further actions.
2. Searches for the IP address elsewhere. If it is not in the cache, it will continue the searching process until it gets to an Authoritative server which has the information.

How does it work?

The Recursive DNS server takes a very important role in the DNS resolution process. As we mentioned earlier, it operates between the user and the Authoritative DNS server. Yet, it completes several crucial tasks. Let’s summarize how it operates and what actions it performs in this vital process: 

• The DNS resolver is the one that obtains the DNS query from the user.
• It then asks the Root server about the location of the TLD (Top Level Domain) server.
• The Recursive queries the TLD (Top Level Domain) server for information about which is the accountable Authoritative DNS server for the precise domain.
• It makes a request to the Authoritative DNS server responsible for the particular domain. 
• The Resolver gets back to the user and provides the requested data.
• It caches the DNS information for further use.

The existence of Recursive DNS servers is crucial. This is because they support the Authoritative DNS servers, which would not otherwise be able to handle the workload created by themselves. Additionally, DNS Resolvers distribute the load of the huge number of user requests and make the resolution of domain names way easier.

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Recursion and Iteration: Explaining the Dynamic Duo

Recursion and iteration are two programming concepts that play a crucial role in the functionality of DNS servers, particularly recursive ones. Let’s explore these concepts:

• Recursion 

Recursion, in the context of DNS, refers to the process where a DNS server, upon receiving a query for a domain name, doesn’t have the necessary information in its cache and initiates a series of requests to other DNS servers to resolve the query. Each subsequent request dives deeper into the DNS hierarchy until the authoritative DNS server for the queried domain is reached.

Imagine recursion as a detective following a trail of clues to solve a mystery. The DNS server starts with limited information, asking other servers for more details until it discovers the complete answer. This recursive process ensures that even if a DNS server doesn’t have the needed information, it can still find and deliver a response after consulting other authoritative sources.

• Iteration

Iteration, on the other hand, involves repeating a set of instructions until a specific condition is met. In the DNS context, iteration occurs when a DNS server sends iterative queries to authoritative servers and, at each step, refines the search until it obtains the precise information needed to resolve a domain name.

Think of iteration as a systematic approach where the DNS server persistently refines its search, step by step, until it comes to the solution. This process allows for efficient querying, minimizing the chances of overwhelming authoritative servers with unnecessary requests.

• Recursion and Iteration in Recursive DNS Servers

Recursive DNS servers blend recursion and iteration to navigate into the complex DNS hierarchy. When a recursive DNS server receives a query, it first checks its cache to see if the information is available. If not, it starts a recursive process, reaching out to authoritative servers and using iteration to specify its search for the required data. This dynamic dance between recursion and iteration ensures that DNS queries are resolved quickly and accurately. 

The Benefits of Recursive DNS Servers

Now that we’ve explained the meaning of recursion and iteration let’s explore the benefits that Recursive DNS servers bring to the table.

• Enhanced Performance and Speed: Recursive DNS servers significantly improve the speed of DNS resolution. Maintaining a cache of previously resolved queries allows these servers to respond promptly to reappearing requests without crossing the entire DNS hierarchy again. This results in faster load times for websites and a smoother browsing experience for users.
• Reduced Network Latency: With their ability to store and reuse resolved queries, Recursive DNS servers help minimize network latency. By reducing the time it takes to get information from authoritative servers, these servers contribute to quicker and more responsive internet connections.
• Improved Security: Recursive DNS servers can protect users from malicious activities. Through features like DNS filtering and blocking known malicious domains, these servers safeguard against phishing attacks, malware, and other online threats. They can perform detailed checks and validations before serving DNS responses, adding an extra layer of security to the online experience.
• Load Distribution and Balancing: Recursive DNS servers contribute to the efficient distribution of network traffic by balancing the load on authoritative servers. These servers reduce the load on the DNS infrastructure by caching and serving responses locally.
• User Privacy: They can enhance user privacy by implementing features like DNS over HTTPS (DoH) or DNS over TLS (DoT). These encryption protocols add a layer of security, preventing unauthorized parties from intercepting and monitoring DNS requests.

Vulnerabilities

Cybercriminals are well aware of the importance of Recursive DNS servers. Unfortunately, they managed to use their vulnerabilities and initiate different malicious attacks. Some of the DNS resolvers are public, which makes them an easy target. Attackers often use DNS spoofing attacks or execute DDoS attacks in order to shut the servers down directly.

• Recursive DNS servers and the amplified attacks

DNS Amplified Attacks are a very common threat on the Internet. They exploit the public Recursive DNS servers to generate high traffic and to damage the target.

• Public (Open) recursive DNS

To leave your Recursive DNS server public is dangerous. Such devices are with minimum security and visible IP address. This means that anyone, including cyber-criminal, can easily access it and later use it as a botnet device to amplify their next attack.
Many of the network administrators don’t know their recursive servers are open, and this can lead to severe problems. If you doubt about your DNS server, you can check it on this page: http://openresolverproject.org

• Oversized packets

A threat that some of the attackers take advantage of is manipulating the query packets. They send multiple queries to recursive servers, but with a modified IP addresses, directing all of the generated traffic towards the victims. They use many servers, and if the traffic is high, they can crush the victims’ servers.

Can you have safe Recursive DNS servers?

Yes, it is possible to secure your servers. We recommend you to use our Private DNS servers. They are hidden from the public eye and still have all of the premium features like TTL management, Cloud domains, Secondary DNS, SOA Settings and Hourly statistics
You don’t need to get all of them. You can strategically choose just a few of them where you most need them.

Conclusion 

The Recursive DNS servers are a fundamental component of the global network Internet and the DNS (Domain Name System). The role they play in the DNS resolution process is significant. DNS resolvers simplify and manage to balance the load of numerous DNS requests daily!

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