Propagation?    It is often mentioned by web hosting companies to their clients... but do any of them tell you what in the world it means? I will try to give you a bit of basic info to help you understand propagation and how it affects your web hosting account.

When you sign up with a new web host, you are told it will take 2 to 4 days for your DNS to propagate to their servers. Well, here is why.

Your domain registry lists all its domains and sends all that information to the Internic registry database. The Internic database is where your web browser, and your ISP, and all other machines that connect and make the Internet work, look to see what sites are on who's servers.
Almost like a phone book that lists your name with your phone numbers, the Internic database lists domain names, and what server they are on.

When you make a change to your name servers listed at your registry, then, the propagation time is the amount of time it takes for them to update that information with Internic, and then all the ISP's and connection routers across the internet need to update with Internic so they know where you moved to.

NOT ALL ISP's and routing points are equal. Some update once or twice a day with the Internic database, some update once a day with their next up-line routing point, and that routing point updates with Internic on a schedule of its own. Some ISP's and routing points may not update for a couple of days. They are all on their own schedule...

With that in mind, your ISP may cache or save in memory, your sites IP number. Then, when you try to go to your site, they can take you right there. However, during the propagation period, it may take you to the old server, until it's up-line routing points and your ISP have updated their Internic information, then, your ISP may still have a waiting period before it refreshes its cache memory, and finds your site at the new location.

That is why your friends may be able to see your site, while you can't, and visa versa. It can take from 24 to 72 hours for the Internic information to be updated across the internet, and during that time, you may or may not be able to get to your new hosting account with your domain name.

However, you can access your site by its new IP number that was also in your welcome e-mail. We put that in your welcome e-mail so you can go in, and set up your e-mail accounts, and upload your sites content so it is ready to go once the DNS has propagated. Why wait twice.

I hope that explains the basics to you so you can understand why your new web hosting account does not work instantly, and what dns propagation is caused from.