DNS is an acronym that stands for Domain Name System. It's also fundamental part of how the Internet operates, and can impact browser speed, website performance, email clients, and much more – but what exactly is it?

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What is a DNS?

A Domain Name System is a database that translates the user-friendly host names that we use to browse the Internet (e.g. plus.net) into a numerical format understood by computers, known as IP addresses (e.g.

DNS is an integral part of how the internet works, as it allows users and hosts to utilise more memorable DNS names rather than having to use a website's IP address to access a website.

What is an IP address?

IP stands for internet protocol, and an IP address is the unique string of numbers that identifies devices that are connected to the internet. Every device, from a smart phone, to a tablet to a router must have one. IP addresses essentially allow one computer to communicate with another.

An IP address is always structured in the same way, using four or six numbers separated by decimal points (.) e.g. or Each unique code holds information on the location of your computer and information on your internet service provider (ISP).

Your device can have either a static or dynamic IP address. A static address stays the same, so is generally considered to be less secure as they are more easily tracked, however these risks can be avoided by safe internet use. A dynamic IP address changes, using a pool of addresses from your ISP that are shared among various computers.

How does DNS work?

When a user wants to access a webpage, they enter the address (or DNS name) into their browser's address bar. This information is then sent in the form of a 'DNS query' to their Internet Service Provider's (ISP) DNS servers. Every ISP has a database of DNS names and their corresponding IP addresses. If a user's initial query can be answered using this directory, an 'authoritative' answer is sent to the user's computer so they can connect with the website.

If the ISP directory is unable to answer the initial DNS query authoritatively, then its next step would be to check its cache. A server's cache holds a record of all other previous queries. If it can answer a user using information from the cache, then it will still answer but with a 'non-authoritative' answer. This means that the information you're being supplied with isn't directly from your ISP's directory, but from a third party.

If your query still can't be answered, then the DNS query process will use recursion. This is when your ISP's DNS survey uses the information it has on other authoritative servers in its root hint files to contact and get the information you need. Once an ISP has requested this information, it is sent to a user's computer, where a connection is formed. The ISP server then stores that information in its cache which can be then accessed for future queries.

Problems with Internet service are often down to an issue with the DNS server – to check any current issues with your DNS status, use our Service Status page.

How can DNS affect your Internet speed?

Although DNS is not directly related to your Internet speed, it can influence how fast an individual webpage appears on your computer. Once a connection has been established though, it should not affect download speeds.

If you want to amend your router's DNS servers however, this can help improve your overall speed. Many apps are available to help you find the best server for your router or computer, including namebench. Once you have your recommended DNS server addresses, you should:

  • Go to your router's administration page
  • Go in to your advanced settings
  • Note down your DNS server addresses for reference
  • Replace them with your recommended DNS server addresses
  • Your device will then be updated with these DNS servers and should give you an improved browsing speed.

How can DNS affect your email?

As well as acting as a record of IP-address-to-host-name mapping, DNS also contains information that can help with other functions, such as email. The Mail Exchanger (MX) record provides the extra information needed to allow emails to be forwarded on to your email server.

An email address is made up of two parts, the recipient (which is you) and the host (your email provider) e.g. david(recipient)@hotmail.com(host). When you send an email, you will either send it directly to the target domain (the recipients email provider) or to another server known as a Simple Mail Transfer Protocol (SMTP) mail server which acts as a 'middle man'.

Find out more about changing your DNS address

Head over to our Help and Support page.

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