A basic introduction…
Web Developers, Hosts and many Web related techies will often speak about DNS (Domain Name System), A-records, MX-records, TTL and DNS propagation as terms that the average person should understand. This article is designed to explain what they all mean in simple terms.
Normally when someone wants a website there are two things they need to purchase, a domain name, and website hosting.
Before I can explain in detail, a short background in website setup is required. Purchasing a domain is just the ownership of the URL and you cannot host a website on a URL alone. For this you need website hosting.
When you search for a website and you type a URL into the address bar, your computer makes a request asking the URL where it should go to find the website. A record will ‘pointrsquo; your computer to a server that contains the website, and the website is then displayed to you on your computer.
What are Nameservers?
Nameservers are the name given to the collection of records that will point a URL to the desired hosting server, including the website and email. This collection is made up predominantly of A-records and MX-records, detailed further below. Here is an example of what nameserver records look like:
There are always a minimum of two. This is so that, in case something becomes corrupted with the first one, there is a backup record that should point to the same server.
Encompased within nameservers are records that point to the website hosting and also to the website email addresses. For example, if you have the URL my website.com, you’ll likely have email addresses like myname@my website.com, and these emails are also dealt with by your hosting company.
What are A-records?
An A-record is the name given to the specific records that make up part of the nameserver records that only deal with the website pointing. These are sometimes required for various reasons: you might want one company hosting your website and another hosting your emails, for example. In this scenario you ignore nameservers and specify both the A-records and MX-records individually. A typical A-record will look like this:
What are MX-records?
Similar to A-records, these work in the same way but deal only with your emails, not your website hosting. A typical MX-record looks like this:
What is TTL?
You might have noticed in the above two pictures that there is a column called TTL. This stands for Time To Live and means that if you are to change this particular record, it might take up to X seconds for this change to work its way through the internet. TTL is generally set to 86400s (24 hours), but can be shorter.
What does DNS Propagation mean?
DNS propagation is the term given to the time taken to make a change in such records. This is similar to TTL above; however, TTL should be the maximum time for the changes to take effect, where DNS propagation is the name given to the actual spread of this new record. The way the internet and world “learns” of this new record is by being sent to hundreds of different servers around the world and in turn sent to thousands more until all servers directing traffic around the internet are aware of this new change and can point people to the right places. This is why, sometimes, when a record changes, one person can see it working before another.
Domain names (URLs) have records that point a user to the right server to see the website or to direct emails to the right server to make their way into your inbox. You can specify nameservers which package up all of these records in one go, or specify them individually, sending them all in different directions. DNS propagation is the name given to the process and time taken for a change in these records to make their way around the internet.