DNS and the great world of TCP/IP

[Ang-Chih Kao <akao@MIT.EDU>]

>Does pi3 gui configuration utility means Pi3web Server Admin ?
Yes.

>Can I have Server Alias for 'AAA' machine as 'BBB' machine. I need
>a single machine to have two names.

Yes, this is what I was describing in the previous email.  It's called
Virtual Hosting by name.

I will assume that you are new to the work of networking and explain some
things:

On the internet (or any network running TCP / IP), each computer gets a
unique IP address.  For example, mine is 18.242.2.32.  If you have a dialup
connection, your IP is probably assigned to you each time you dialup.

This is how each computer sees itself and other on the internet.  When you
retrieve a webpage from say Yahoo, it uses the IP address for the yahoo
server to send a request.  Then the Yahoo server uses your IP address to
send you the webpage you requested.

It's true that you can also access Yahoo by www.yahoo.com.  In this case,
what happens is that www.yahoo.com has to be translated into an IP address.
 So, for your computer to find the IP address, it goes through several
sources -- the main one being a DNS (Domain Name) server.  A DNS server has
a list of names(ie. www.yahoo.com or www.netscape.com) and their IP addresses.

Suppose that www.yahoo.com's IP address is 23.23.23.23.  And also suppose
now that Yahoo realizes that there are freaks out there who are typing
web.yahoo.com by accident.  And Yahoo doesn't want to make these people
type www.yahoo.com.  So what Yahoo can do is they can add another entry to
the DNS that says web.yahoo.com's IP address is also 23.23.23.23.

So, what happens when a browser requests a page from www.yahoo.com or
web.yahoo.com?  The same thing.  The requests are sent to the same server.
I believe this is answers your question.  What this means that it is beyond
your control if 'AAA' and 'BBB' are both sent to the same IP address
(meaning the same computer).  

Now, what if Yahoo realizes that people going web.yahoo.com should be told
that they are freaks?  But both web.yahoo.com and www.yahoo.com are going
to the same server?  Yahoo can't just have it tell everyone they're freak,
just the ones going to web.yahoo.com.  What they can now do is set up a
"Virtual Host by Name" on their nifty Pi3 web server.  By setting up a
different webroot, yahoo can display one page to people going to
www.yahoo.com and another for web.yahoo.com.

You stated that you want people going to 'AAA' and 'BBB' to recieve the
same page, well in this case you don't need to setup a "Virtual Host by
Name".  But you have to make sure that in the DNS, both 'AAA' and 'BBB' are
pointing to your IP address.

Note, the DNS system is rather complicated.  It's not possible for you to
run your own DNS and expect people on the Internet to follow your DNS.
However, if you are running your own TCP / IP network, and everyone on the
network uses your DNS, then yes.

Once again, most of this has been stated in past messages on the support
archive.  Hmm, maybe I should just point people to specific messages from
now on...

Kao.

Hey guys, did I miss anything?