IP addresses are always 32-bit numbers. As we illustrated in section 1 of this movie, those 32-bit numbers can be represented in a variety of ways, and we suggested that the popular - "dotted decimal" - notation was the most widespread. The example that we used looked like this:
192.168.0.2
Your computer can very easily convert that format into the binary format that works best with its hardware.
There is another popular way to represent an IP address. You've probably seen IP addresses that look like this:
www.yahoo.com
www.google.com
webmail.smithcompany.com
printer1.smithmachines.org
When an IP address is represented in that format, it is called a - "Domain Name" address. Obviously those IP address representations can be more meaningful and more memorable to humans. Unfortunately, your computer cannot convert that format into the binary format that your hardware needs unless it gets help from some kind of - "higher intelligence" that's aware of the domain names chosen by humans. Internet designers long ago implemented an automated, easy mechanism for translating back and forth between the two formats. The mechanism relies on computers running special processes called - "Domain Name Servers" - (DNS) - that have a highly evolved intelligence optimized for converting IP addresses back and forth between Domain Name and Dotted Decimal representations. (Often these services are supplemented with the names of your ISP's devices, and are relayed through the routers made available by your Internet Service Provider). Whenever you want to use an Internet address like "www.google.com", your computer automatically contacts a Domain Name Server and asks for help translating it to a dotted decimal address, which it remembers for awhile, and uses for subsequent message transmission.
Accordingly, all of the computers and other network equipment on your LAN will want to know the numeric IP address(es) of one or more Domain Name Servers that can answer requests for address translation services. Your Internet Service Provider should host one or more DNS servers for your use, and the DHCP protocol will work with your router's preprogrammed, - "default" - behavior to make this information available. If you are using the DHCP protocol everywhere, you should never need to specify a DNS Server address value.
Configuration Example using Windows XP
Let's use Microsoft's well-known - "Windows XP" - operating system as an example to show how to configure an Internet connection. From the - "Control Panel" - facility, select "Network and Internet Connections". From there, click on "Network Connections". That will result in a frame like this, showing a list of all of your network interfaces:
Click on the icon representing the network interface that you want to configure with an IP address. Usually it will have a name like - "Local Area Connection". (If your computer has only one network interface, then the list will show only that single entry. Double-click on it.)
A new frame, named - "Local Area Connection Status" - will appear as follows:
From the prominent - "General" - tab, select the button labelled - "Properties".
A new frame, named - "Local Area Connection Properties" - will appear as follows:
That frame will be dominated by a list under a title that says "This connection uses the following items". From within that list, doubleclick on - "Internet Protocol (TCP/IP)".
A new frame, named - "Internet Protocol (TCP/IP) Properties will appear as follows:
From the prominent - "General" - tab, select - "Obtain an IP address automatically" - and - "Obtain DNS Server address automatically".
Click "OK" and close all of the open frames. Your PC is configured for Internet Access!
Conclusions
Modern NAT routers include a - "Dynamic Host Control Protocol" - (DHCP) server that makes it very easy to configure all of the other computers in your local area network for Internet access. It is easy to configure your Personal Computers and other network equipment to use this protocol to ask your router for all of the details they will need to become Internet compatible. Your router will use this same protocol in turn, to ask your Internet Service Provider for the information it needs.
