I am busy doing a bit of research into developing a blogging service of sorts and should not quite work out how services handle custom domain names. Particularly around the technical side how can they route visitors to an interior mapping (helloworld.tumblr.com) without redirecting?

It appears like Tumblr perhaps you have point your An archive in a static IP while Wordpress perhaps you have use their title servers. If anybody knows about this stuff would you shed some light how they make this happen and when you will find pros/cons towards the different techniques?

Thanks ahead of time!

You need to consider "mass virtual hosting" for apache and nginx to learn more relating to this. For instance, a fast explore stackoverflow produced this: