To understand the TCP/IP protocol, let's start by examining a more simplified numbering protocol: the telephone system.
When you place a long-distance phone call, you first dial the area code and then the local number. (The analogy holds up just fine if you substitute country codes; North America uses area codes, and since my typewriter is on that continent, I'm going with area codes here.) Your call won't connect with the desired recipient if you decide to dial the area code after you dial the seven-digit number. Why? Because dialing the area code first, not last, is part of the set of rules, or the protocol, of telephone communication.
Every network-ready computer on the Internet has a unique Internet Protocol (IP) address, just as every telephone in the world has a unique telephone number. When your computer knows another computer's IP address, the two computers can start exchanging information. So just how does your computer obtain this IP address? There are many possibilities, but essentially, IP addresses are assigned in only one of two ways: manually or automatically.
We'll talk about automatic configuration in just a bit. For now, understand that manual IP address configuration is as straightforward as it sounds: you open up a Properties dialog box and assign the IP address with your keyboard. To do so, follow these steps:
Now, before you just start typing numbers here, understand that these have to be very specific numbers, or your system won't be able to communicate with other systems. Most times, a manually configured address is assigned by a system administrator, and in rare instances, an ISP. If you just typed in the numbers shown here, your computer would be able to talk with others only by dumb luck.
You will also fill in values for the subnet mask, default gateway, and possibly the Domain Name Server (DNS, explained later) addresses. If you choose to specify an IP address manually, you must specify a DNS server address manually as well.
But what's the significance of these values? Glad you asked.