DNS: Its Definition, Functions, How It Works, and Types

What is DNS? DNS is a crucial networking system that translates easy-to-remember domain names into numerical IP addresses. This article explains the definition, function, workings, advantages, disadvantages, and types of DNS, such as resolver, authoritative, recursive, and caching servers. DNS facilitates easy access to websites and online services, providing ease of use, scalability, and high availability through data replication and redundant servers. However, DNS also has some drawbacks, such as server dependency and security issues.

What is DNS

What is DNS? The DNS network management system is often compared to an internet phone book. In data communication, every device connected to the internet has a unique IP address so that other machines can find it. This “internet phone book” (DNS) makes it easier for humans to remember complex IP addresses, whether they use IPv4 or IPv6 technology. When someone visits a web page, they access information through a domain name, such as telkomuniversity.ac.id. The browser then interacts using the IP address. The function of DNS here is to translate the domain name into an IP address so that the browser can load information from the internet. The server application responsible for the process of translating hostnames into IP addresses is the DNS server.

DNS stands for Domain Name System. It is a component in the network infrastructure responsible for translating memorable domain names into unique numerical IP addresses. The DNS server plays an important role in network addressing, as it allows users to access websites, online services, and other network resources by using domain names instead of having to memorize long numerical IP addresses.

DNS servers store information in databases called DNS zones. Each DNS zone contains records that map domain names to their corresponding IP addresses. When a user enters a domain name in a web browser or app, the device sends a request to the DNS server to obtain the IP address corresponding to the domain name. The DNS server then responds to the request by providing the correct IP address. DNS servers store information in databases called DNS zones. Each DNS zone contains records that map domain names to their corresponding IP addresses.

DNS Servers Involved in the Web Page Loading Process

Generally, DNS servers operate in a hierarchy consisting of several types of servers. Four DNS servers are involved in the process of loading web pages:

1. DNS Root Server: The DNS root server is at the top of the DNS hierarchy and functions to provide information about the location of authoritative servers for top-level domains (TLDs) such as .com, .net, .org, and so on.
2. DNS Top-Level Domain (TLD) Servers: DNS TLD servers are responsible for top-level domains such as .com, .net, .org, and so on.
3. DNS Authoritative Servers: A DNS authoritative server stores specific information about the domains that the server is assigned to manage.
4. DNS Resolver Servers: DNS resolver servers act as intermediaries between the user and the DNS server to retrieve the required IP address information.

DNS Functions

DNS (Domain Name System) has several important functions in the network infrastructure and internet addressing. Here are some of the main functions of DNS:

• Domain Name Translation: The primary function of DNS is to translate memorable domain names into unique numerical IP addresses. When a user enters a domain name in a web browser or application, DNS handles the request and returns the IP address corresponding to the domain name. This allows users to access websites, online services, and other network resources using the domain name instead of having to remember a long IP address.
• Route Information Dissemination: In addition to translating domain names, DNS can also be used to store and disseminate information about network routes. In this scenario, DNS serves as a server for records that link network or domain names with destination IP addresses. When a user sends a packet to the destination address, DNS provides information about the route the packet should take.
• Service Discovery: DNS can also be used for service discovery on the network. In this case, DNS keeps records that associate the service name with its associated IP address and port. For example, in the Voice over IP (VoIP) protocol, DNS can be used to look up the IP addresses of available VoIP servers.
• Caching: DNS caching is a temporary data storage process performed by a DNS server. DNS caching stores data closer to the client, so the DNS request process can be executed faster, reducing bandwidth or CPU consumption. Imagine you frequently visit the website it.telkomuniversity.ac.id. Every time you type that address into your browser, your computer needs to find the website’s IP address to access it. This process involves DNS, which works like an internet phone book, matching domain names with IP addresses. DNS caching occurs when your computer or device stores this DNS information temporarily. So, when you type it.telkomuniversity.ac.id again, your device doesn’t need to contact the DNS server to find the IP address because it already has the information in the cache. This saves time and bandwidth, increasing website access speed. DNS servers can perform caching, or temporary storage, of received information. When a DNS server receives a request to translate a domain name, it tries to find the corresponding record in its cache before sending the request to another DNS server. If the record is found in the cache, the server can return the result directly without having to search other servers, saving time and bandwidth.
• Redundancy and Availability: DNS also plays a role in providing availability and redundancy in the network infrastructure. With multiple DNS servers and data replication, if one DNS server is unavailable, requests can be routed to another DNS server that has a copy of the same data. This ensures that the DNS system remains operational even if there is a failure on a particular server.

The above functions make DNS a critical component of internet addressing and ensure that users can easily access and use various services and resources on the internet using only memorable domain names.

How DNS Works

The way DNS (Domain Name System) works involves several steps and various entities in the network infrastructure. Here are the general steps in the DNS process:

 

DNS Request

When a user enters a domain name in a web browser or application, the user’s device sends a DNS request to the nearest DNS server configured in the network settings. These DNS servers are referred to as DNS resolvers.

Inquiry to DNS Resolver

The DNS resolver receives a DNS request from a user device and checks if the requested information is available in its cache. If the information is in its cache, the DNS resolver will return the corresponding IP address without needing to send the request to another DNS server.

Inquiries to Hierarchical DNS Servers

If the requested information is not in the DNS resolver’s cache, the DNS resolver will send the request to the next DNS server in the DNS hierarchy. Usually, this is a DNS server set up by an internet service provider (ISP) or a top-level DNS server referred to as a DNS root server.

DNS Lookup

A DNS server that receives a DNS request will try to find the requested information by performing a search (query) through the DNS hierarchy. This process involves a series of requests and responses between DNS servers until the requested information is found or determined to be unavailable.

DNS Response

Once the DNS server finds the requested information, it sends a response to the DNS resolver that originally sent the DNS request. This response contains the IP address corresponding to the requested domain name.

IP Address Return

The DNS resolver receives the DNS response from the DNS server and returns the corresponding IP address to the user device that originally sent the DNS request.

Access to Resources

The user’s device uses the received IP address to access the resource in question, such as a website, online service, or other network resource.

The above process takes place in milliseconds and is usually invisible to the user. Each time a user enters a domain name, the DNS system automatically manages the request and returns the corresponding IP address. DNS responses are usually stored in the DNS resolver’s cache for a period of time. This allows faster access to the same information if a similar request is made in the future.

Advantages and Disadvantages of DNS

Advantages of DNS

Ease of Use

DNS allows users to access websites, online services, and other network resources by using easy-to-remember domain names, such as www.example.com, instead of having to remember long and complex numerical IP addresses. This makes using the internet more intuitive and practical.

Scalability

DNS allows data replication and distribution of DNS servers across the network. This provides redundancy and high availability, so that if one DNS server is unavailable, requests can be redirected to another DNS server. This ensures that the DNS system remains operational even in the event of a failure of a particular server.

Redundancy and High Availability

DNS allows data replication and distribution of DNS servers across the network. This provides redundancy and high availability, so that if one DNS server is unavailable, requests can be redirected to another DNS server. This ensures that the DNS system remains operational even in the event of a failure of a particular server.

Caching

DNS servers can perform caching, or temporary storage of received information. When a DNS server receives a request to translate a domain name, it will try to find the corresponding record in its cache before sending the request to another DNS server. If the record is found in the cache, then the server can return the result directly without having to search other servers, saving time and bandwidth.

Service Discovery

DNS can also be used for service discovery on the network. In this case, DNS keeps records that associate service names with their associated IP addresses and ports. For example, in the Voice over IP (VoIP) protocol, DNS can be used to look up the IP addresses of available VoIP servers.

Renewal Management

DNS allows management of updates and changes to information related to domain names. DNS administrators can update DNS records to point domain names to new IP addresses or change other DNS settings. These changes can be quickly and easily applied across the network.

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Disadvantages of DNS

Dependency on DNS Servers

DNS relies on DNS servers to translate domain names into corresponding IP addresses. If a DNS server experiences problems or failures, it can cause disruption of access to internet resources. Reliance on DNS servers makes the system vulnerable to service interruptions or DDoS (Distributed Denial of Service) attacks.

Speed and Latency

The DNS process involves several steps involving queries and responses between DNS servers. This can affect the time it takes to complete a DNS request and return the corresponding IP address. Network latency or excess traffic can also affect DNS performance and result in delays in IP address retrieval.

Inconsistent Caching

While caching can speed up DNS responses by storing received data, it can also cause problems when there are information updates. If there is a change in the IP address associated with a domain name, some users may still receive outdated data from their cache, causing inaccurate or failed access.

Security

DNS can be vulnerable to DNS spoofing or cache poisoning attacks, where false or unauthorized DNS information is placed in the DNS cache. This can lead to users being redirected to the wrong IP address or being involved in phishing or other attacks. Protection against such attacks requires additional security measures.

Lack of Privacy

By default, DNS queries and the data sent in the process can be visible and recorded by internet service providers (ISPs) or other third parties. This can reduce user privacy and allow the collection of data about browsing habits and preferences.

Scalability Difficulties

In some cases, DNS management and scalability are complex, especially if the network infrastructure is very large and complex. Improper setup and configuration or lack of capacity can lead to poor performance or difficulties in maintenance and management.

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Types of DNS

There are several types of DNS that serve specific purposes within the network infrastructure. Here are some common types of DNS:

DNS Resolver

A DNS resolver is a type of DNS that functions as a DNS client that sends DNS requests to a DNS server and receives its responses. The resolver is responsible for translating the requested domain name into a corresponding IP address. Resolvers can be local resolvers installed on user devices, such as computers or routers, or resolvers managed by ISPs or DNS service providers.

Authoritative DNS Server

An authoritative DNS server is a type of DNS that serves as the source of truth for DNS information relating to a particular domain name. It maintains DNS records containing information about the domain name, such as the associated IP address, and provides accurate DNS responses when queried by resolvers or users.

Recursive DNS Server

A recursive DNS server is a type of DNS that is responsible for performing a complete resolution process for received DNS requests. When a resolver sends a DNS request, the recursive DNS server will perform a lookup to find the corresponding IP address by performing the necessary steps, including contacting the authoritative DNS server if needed.

Forwarding DNS Server

A forwarding DNS server is a type of DNS that is needed when the resolver cannot find the corresponding IP address in the local cache or authoritative DNS server. Forwarding DNS servers take DNS requests from resolvers and forward them to other DNS servers, such as ISP resolvers or other authoritative DNS servers, to obtain correct DNS responses.

Caching DNS Server

A caching DNS server is a type of DNS that temporarily stores (caches) DNS responses received from authoritative DNS servers. When a resolver sends a DNS request, the caching DNS server first checks if the requested information exists in its cache. If it does, the server will return the response from its cache, reducing the time and latency required to look up the information from the original source.

Primary DNS Server and Secondary DNS Server

Primary and secondary DNS servers are types of DNS that work together in a redundant configuration. A primary DNS server is the main source of truth that stores DNS records for one or more domain names. A secondary DNS server, on the other hand, is a replica of the primary DNS server that is used as a backup in case the primary server fails. Secondary servers regularly duplicate and synchronize information from the primary server to ensure the availability and reliability of the DNS service.

Tertiary DNS Server

A tertiary DNS server is a type of DNS that acts as an additional backup in a redundant DNS configuration. It is a server whose existence is optional and serves as a third backup if the primary and secondary servers are not available. Understanding what is DNS is fundamental to grasping the role of a tertiary server. These DNS types have different roles and functions in a network infrastructure, and a combination of several types is used to provide reliable, fast, and secure DNS access.

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