DNS stands for Domain Name System and is a critical component of the Internet. It is responsible for translating human-readable domain names (such as ”example.com”) into an IP (Internet Protocol) address, which is used for computers to communicate with each other.
DNS works as an intermediary between a domain name and the IP address linked to it. Every website, service, and resource connected to the Internet has a unique IP address associated with its domain name. When someone types a domain name into their browser, DNS is the technology which looks up the correct IP address and sends the data to the correct destination.
The system is made up of different types of DNS servers, details of which are maintained by your ISP. These DNS servers are placed all over the world and are run by various online organisations. Every time a person tries to access a website, the content request is sent to the nearest DNS server, which then queries the master DNS server to find the IP address related to the domain name and transmits the information back to the end user.
The core of the DNS system is the Domain Name Registries and Registrars, which are the companies that your domain registrar registers with in order to acquire the domain name for you. There is an authoritative server for each top-level domain for example; .com, .net, .org, .uk etc. Your Domain Name Registrar will link your domain name to the authoritative server responsible for the particular top-level domain (TLD) which your domain name is based in.
The DNS ‘root’ servers are the core ‘authoritative’ servers and are managed by the likes of Internet Corporation For Assigned Names and Numbers (ICANN). This is how the internet works as a whole, with top-level domain names and DNS root servers being controlled by organisations like ICANN.
To access the site, the browser looks at the end of the domain name and if it finds a valid top-level domain, then it queries the ‘root’ nameservers for the relevant authoritative server for that top-level domain. Once it has the address of the authoritative nameserver, it then queries this server to find the IP address associated with the domain name.
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The DNS system is designed to be resilient and remain active even in the event of a failure of one or more of its component parts. This is why the authoritative server for each TLD is maintained in multiple locations around the world - in case one server goes offline, then another can take its place. This ensures that the internet remains operational even if one component fails.
Optimising the DNS system to ensure the best possible performance is always a concern for all organisations running websites. This is where DNS caching comes in. A DNS cache stores a record of all the DNS lookups that have recently been performed so that if a query has already been made, the result can be returned more quickly. This reduces the time taken to load a website since the DNS lookup will already have been performed. DNS caches can be stored at the ISP level or at an organisation’s web servers.
For large organisations or companies running websites, DNS load balancing is an important task to consider. By spreading the load across multiple DNS servers and locations, the site can remain active even if one server is down. This helps ensure that the website stays up and running at all times.
DNS records are also used for more than just IP address lookups. They can be used to configure email servers and certain system functions, such as which server hosts a particular public service. DNS also has a role to play in website security - for example it is possible to create an SPF, or Sender Policy Framework, record with DNS to validate that emails from a particular domain are from an authorised server. They can also be used to specify which servers emails should be directed to, thus reducing the risk of a malicious attack on the mail servers.
For those people or organisations who are looking to get the best performance from their website, there are a few general guidelines and best practices to follow. The most important one is to ensure that DNS records are up to date and properly maintained, which includes setting the Time to Live (TTL) correctly and monitoring the load levels on the servers. For those with multiple servers, load balancing should be used and servers tested regularly to ensure they are performing optimally.
For those who want to protect their websites, they should also set up DNSSEC, or Domain Name System Security Extensions, which create an additional layer of security by using cryptography to authenticate and validate the data in DNS records.