Tuesday, October 7, 2008

Beware of free DNS services

Businesses come in all shapes and forms. Many small businesses are sole traders, often working on a shoestring budget. When businesses of this size first create a web presence it is often done on free services like Geocities or Blogspot. Sometimes this is because they are trying to minimize costs, and sometimes it is because they wandered into a web presence by accident. Although I am an IT professional, and have my own cheap hosting, this blog started as a very personal diary that I later split into three, distributing the back articles; one of the child blogs is decidedly business related. Once a blog or mini-site becomes part of a business' identity it really needs to be under the business' branding and this usually means having its own domain name to build recognition of the business, avoid confusion with the other sites on the free host, and present a more professional image.

When a domain name is registered it needs hosting. Sure, there's lots of cheap hosting out there, but while registrars will offer advertising supported free hosting or expensive paid hosting they seldom point their customers towards the cheap offers. There's a number of reasons for this, but as cheap hosting is often unreliable or offered by unstable companies the registrars can be forgiven for not wanting to damage their brand by recommending an unsuitable option. Most registrars do offer free mail and web redirection to your existing free hosts, so it is the easy option to redirect mail on the domain to your existing free web mail service (e.g. Google's Gmail) and redirect web page views to your already established free service. They do this by providing the Domain Name Server (DNS) for your domain on one of their servers. When a surfer or another computer wants to contact your site, the DNS gives the address of the machine where your site is, in this case they hand out the address of one of their own machines, they also supply a web server on that machine that receives the initial request and forwards the browser on to the free service and a mail server that receives incoming mail and sends it on to Gmail.

In order to make the service affordable to them, free web hosts have to limit and standardize the resources the offer and usually give away their free status, through having adverts as Geocities does, an obvious format as Blogspot does, the URL you use for your pages or they just aren't flexible enough for your site's needs as it grows.

The next step is to buy some cheap hosting and change your site over use the DNS supplied by the hosting company. Here's where things suddenly go wrong for you. The DNS system works because the address information is cached in servers all around the net. When you change the master DNS for a domain, it doesn't immediately change, the first delay is that it takes time for the master DNS to load the new DNS address for your domain, then there is a much bigger delay before all the caches that are holding your old address flush that information and need to refresh the information about your domain.

For two or three years your registrar has been quietly forwarding your email and sending people to your free website for as long, so it seems reasonable to expect it will keep forwarding for the few days the change-over takes, but the reality is different and the moment you change your DNS to a different provider, they shut off this service. The cut-off is immediate and doesn't even wait for the master server to load your new DNS. There's no technical reason for this, it's just the way that every registrar I've ever worked with handles the process.
The effect of this is severe, your website will suddenly go dead and any email for your domain will bounce back to the sender, making your site seem to have simply gone away. Usually this will last for anything up to 72 hours (or more), with some people being able to access you through the new DNS sooner. In a final touch of irony, the more popular your domain is, the greater the chance that its addresses will be cached. If Murphy's awake and the missing email is an important business email you may well lose whatever business this mail involves and at the minimum you will appear less professional in the eyes of affected customers.

The easiest way you can avoid this problem is to move your site off your registrar's DNS long before your site becomes popular. If it is too late for that, try and schedule the change for a long weekend. You can also check out their control panel to see if you can change the DNS to point MX (Mail) and A (Address) records at your new server. You'll still get some down-time, but not as long. One thing you can do to try and further reduce the negative effects is to co-ordinate your change with the master DNS' reload cycle.

Every top level domain name (.net, .uk, .nz) has its own cycle for loading changes to the DNS for domains. Some do it continuously as domains change so you can't synchronize, others do it at fixed times of day. The .nz master DNS is reloaded every hour on the hour (nominal - it actually takes a few minutes to process), so if you change your DNS at five past the hour, your registrar will suspend its services at 5 past the hour and your domain will be completely dead for the following hour, on the other hand if you change the DNS at 5 to the hour, you will only be completely dead for 10 minutes.
I have previously published a shorter version of this posting on Qassia.

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