Web Forwarding - How is it done ?

[Kevin Darcy]

Steve Tobin wrote:

> I am currently working my way through 'DNS and BIND' but nowhere can I
> find an answer to my question.
>
> Many Domain Registration companies offer 'Web Forwarding' which appears
> to redirect a domain name to a given URL e.g. http://www.newdomain.com
> goes to http://www.anotherdomain.com/newdomain ("Park your domain at
> your ISP's free web space" they say).
>
> Does this really work and if so how do they do it ?
>
> Hoping someone can help !

This is possible using a combination of 1) "virtual hosting", where the
web server inspects the "Host" header of the incoming HTTP request, and
manipulates or translates the URL based on its contents and
2) HTTP redirects. So "www.newdomain.com" gets translated within the web
server to, say "www.virtualhost.com/newdomain", which is then redirected
to "www.anotherdomain.com/newdomain". Some proxies and/or firewalls
provide similar capabilities. The reason you can't find a specific
reference in the DNS literature is probably because no DNS trickery is
involved here: "www.newdomain.com" could just be an alias for the
"real" name of the virtual-hosting web server, or even just an A record
that happens to point to that server's IP address.

(Note that the term "virtual hosting" is sometimes also used to refer to
the ability of most modern web servers to respond differently depending on
which interface/address of a multi-homed machine the HTTP request is
received. Sometimes the two are distinguished as "hardware" versus
"software" virtual hosting, but I find that nomenclature confusing since
often the "interfaces" on which the web server is listening are just
"virtual" interfaces implemented in software anyway and prefer the term
"interface-aware").


- Kevin