What does DDNS mean? Definition and how it's used

DDNS is a vital part of the process that ensures the data you want to access from the internet arrives at your computer and not someone else's. 

As it's such a key component of the information transfer process, it's important to know exactly what it is – and this guide will let you in on everything you need to know. 

What is a DNS?

Confusingly, DDNS is actually an acronym within an acronym – it's technically short for 'Dynamic DNS'. It's crucial to understand what a DNS is before moving onto DDNS. DNS stands for 'Domain Name System', which is called into action every time you make a request for some sort of information over the internet. 

For information to be sent and received in a vast network of interconnected devices, there needs to be some sort of address system to ensure it gets to the right place in a consistent and efficient manner – similar to houses and post.

This is what IP addresses are for. Every computer and website has an IP address – which is just a sequence of numbers – that is unique to it, providing a destination for data packets. 

However, even individuals with excellent memory recall capabilities would be hard-pressed to remember just a small number of such addresses – a long sequence of random digits isn't very memorable. This is where a DNS comes in. 

A DNS essentially assigns this string of numbers to a web address that is recognizable, memorable, and comprehensible to any human using a computer. It's the reason you see www.google.com rather than a collection of digits separated by full stops – the hostname stays constant for users, but is converted into something your computer can read, almost like a dual-level postal service.

See our What is DNS guide for more information on this topic.

The four types of DNS server need to make a request

There are millions of DNS servers across the world. Internet service providers have their own domain name systems, and the IP address of popular websites can even be held locally to speed the process up. DNS servers can query one another for an address and can search several until they find it. 

It generally takes four just to load up a webpage, with some performing multiple tasks. Broadly, different types of DNS deal with different parts of a web URL.

  1. DNS recursors respond directly to the initial DNS request and check if they have the domain name saved. If not, they ask other DNS servers if they have the hostname for a given IP address. 
  2. Root name servers return lists of hostnames when presented with an IP address – this is the part of the process where the translation occurs. 
  3. Top-level domain servers deal with the part of the web address known as the top-level domain – the '.com' or '.org' bit at the end of every URL.
  4. Authoritative name servers find the exact IP address that the original hostname request made by a user refers to and then delivers it to the recursor.

What is DDNS and why is it useful?

Now you're aware of what a DNS server is, we can move onto a major distinction: dynamic and static IP addresses, as well as the precise role that DDNS plays in your browsing experience. 

Dynamic and static IP addresses

As was previously mentioned, the D in DDNS stands for dynamic – making the full acronym 'Dynamic Domain Name System.'

Most IP addresses are dynamic, meaning they change/you're given a new one pretty much every time you turn your computer on. They are assigned by a DHCP (Dynamic Host Configuration Protocol) server every time a device makes a request. DHCP servers sit in between devices and DNS servers.

Dynamic IP addresses are the opposite of static IP addresses. These are matched to hostnames and stay constant. In the early days of the internet, Static, unchanging IP addresses were more common, and you can still obtain them via DCHP by temporarily leasing them. 

The problem with static IP addresses is that they're expensive to obtain from your internet service provider. This leads to them usually being reserved for large business entities like Google. Everyone else is assigned new ones regularly by their internet service provider, who has hundreds of thousands of individuals' addresses to deal with.

The role of DDNS

The constant stream of users being paired to new IP addresses every time they log on thanks to DHCP would, without DDNS, pose a problem for anyone wanting to pair an IP address to a hostname.

DDNS services keep hostnames up to date with the latest dynamic IP address. This way, IP addresses can change as much as they like without causing any confusion or deeming requests for information unsuccessful.

If DDNS didn't exist, DNS records would have to be updated manually every time a connection is made.

DDNS services are really useful for smaller businesses who can't afford static IP addresses for their websites, so they require a solution that will keep their hostname paired to their latest one. They are also a great solution to the problem of accessing files on your home network (which are usually assigned public, dynamic IP addresses) from elsewhere, and some gamers use them in order to host game servers. 

Case study: DDNS and security cameras

DDNS is widely used in the security sector as it helps people access certain CCTV cameras. Some CCTV cameras are IP based, meaning they relay images and receive commands over an internet protocol network.

With DDNS, their feed can be accessed when a business owner is away from the warehouse or shopfront, and they don't have to pay through the teeth for a static IP address just to keep their business safe when they're not there. 

How do you sign up to a DDNS service?

Sorting yourself out with a DDNS service is not as difficult as it may appear – you can download a free DDNS service from the internet without much fuss. 

One of the best VPNs in the business, ExpressVPN, recommends a DDNS service when using their Mediastreamer tool, illustrating its broad range of uses. The provider suggests Dynu, but there are plenty of other services out there you might want to try.

DDNS services

This is by no means an exhaustive list of organizations that provide DDNS services, but if you're looking into investing in one, here's a quick rundown of a couple of widely-used, reputable ones.

Let's have a look at ExpressVPN's pick first. Dynu is a reliable DDNS provider and has multiple servers around the world for fast connections. As you can tell by their concise, clear instruction page, it's not too difficult to set up. 

No-IP also has a large fleet of servers – over 100 worldwide in fact – making them another solid option if you need a DDNS service. This is probably the best option to go for if you're new to the technical side of the computer and networking world; the interface is visually excellent, and it's quite difficult to put a foot wrong due to this. Just like Dynu, they also have a great instructions sheet available on their site

DuckDNS, on the other hand, is hosted on an Amazon virtual private cloud and is another option worth looking at, especially if you can't find one that works with your OS. DuckDNS can be used on any platform you choose, including many different types of router. 

Conclusion

This guide has looked at DDNS in a little more detail, but if it's left you with more questions than answers about things like DHCP and IP addresses, more information on these topics can be found below:

Written by: Aaron Drapkin

After graduating with a philosophy degree from the University of Bristol in 2018, Aaron became a researcher at news digest magazine The Week following a year as editor of satirical website The Whip. Freelancing alongside these roles, his work has appeared in publications such as Vice, Metro, Tablet and New Internationalist, as well as The Week's online edition.

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