Why do I have to wait for my domain name to "propagate"?
When you type a URL into your browser, your computer needs to find out which server has the information you want. It does this by using the Domain Name Server, or DNS. This system defines a way to map a domain name, such as wiki.net5.com.au, into an address that computers can use to identify each other, known as an IP address. It's much the same as if somebody were to ask where you live, and you give them your street address.
The system is hierarchical. A number of servers, known as the 'root servers', look after the top-level domain (TLD) servers — those responsible for providing the IP address for the .com addresses, for example. These in turn provide the addresses for all domains in their top leve, such as google.com. Each domain is then responsible for managing any subdomains for this domain, such as mail.google.com.
While it's possible to start at the root servers and work your way out to find a subdomain, this would be incredibly slow. To improve performance of the domain lookup process, most ISPs provide their own DNS cache servers. Users request the addresses for domain names from the cache server – if it knows the address, it returns it immediately; otherwise, it finds it from the relevant machine.
While this is great for regular use, it's a pain when you want to change your domain name to Net5. Your site will have moved over to its new home, but those users who have visited your site (or in fact, all visitors from that ISP) will still be directed to your old host!
Along with the mapping between domain name and IP address, DNS systems contain additional data that instructs these ISP cache servers how long to hang onto this information before updating the cache. The ISP can also override how long it maintains its cache for before updating it. As a result, it can take some time before your visitors end up at your new site.
What can I do about it?
Sadly, the answer is “not much”.
The best thing you can do is to make sure that your sites is identical on both the new and old hosts. Database-driven sites can be particularly challenging.
If you need help migrating your site across, you're always welcome to contact us.