Rethink of the Browser URL

I am reading some network stuff such as Oracle Net used in Oracle database driver, the linux nc command, firewall rules, etc. Basically with so many kinds of network protocols and services, the underneath layer is the same TCP/IP layer. Depending on which network layer you are changing, the effects will apply to all the services above that layer. So if a firewall rule is on the network layer, all the upper layer services such as HTTP, FTP, etc will be affected.

Now looking at the brower URL, http://www.google.com for example. The "www.google.com" part is basically an IP address so it is in the network layer. The "http" part is the application layer. So these two are the bricks of this whole URL thing that the brower needs. Of course, the brower needs a port number. But it can just use the default number 80.

One interesting thing I read about the linux "nc" command is that you can submit an email manually like the following:

$ nc localhost 25 << EOF
           HELO host.example.com
           MAIL FROM: 
           RCPT TO: 
           DATA
           Body of email.
           .
           QUIT
           EOF

So you just need to use the correct format of a given protocol on the designated port to use the service that uses the protocol.