"No exceptional circumstances whatsoever, whether a state of war or a threat of war, internal political instability, or any other public emergency, may be invoked as a justification of torture." -- U.N. Convention Against Torture
We all know what an IP address is--at least, I assume we do. What a lot of us may not know is what they mean. This guide aims to teach you just that.
If you don't know what an IP address is, it's a 32-bit decimal that is normally written as four numbers between 1 and 255 (8 bits, or 1 byte, each), separated from each other by decimal points, and uniquely represents your connection to anything.
Let's take a look at a random, made up IP address. We'll use 22.214.171.124 as our example. First, let's determine what "class" this IP address is...
Class A: 0.0.0.0 to 126.96.36.199
Class B: 188.8.131.52 to 184.108.40.206
Class C: 192.0.0.0 to 220.127.116.11
Class D: 18.104.22.168 to 22.214.171.124
Class E: 240.0.0.0 to 255.255.255.255
We see that our IP address is a class B IP address. Why does this matter?
The reason IP addresses are separated into "classes" is because different classes denote different types of networks or machines. For example, almost all ISP's use class B networks (they use systems that use the class B addressing standard). What is the "class B addressing standard," you ask? Well, let's look at all the standards:
A Uses the first 8 bits for network ID and last 24 bits for host ID.
B Uses the first 16 bits for network ID and last 16 bits for host ID.
C Uses the first 24 bits for network ID and the last 8 bits for host ID.
D Represents a 32-bit multicast group ID.
E Currently not being used.
Now, since this guide is indeed titled "IP Addresses: A Brief Look," I won't get into what that means too much. Just know that's what makes different classes of IPs, well...different. For example, let's say you have dialup. Every time you connect to your ISP and acquire your IP address, you should notice that the first two octets of your IP address never change, while the second two do. Why is this you ask? Because you have a class B IP address, which uses the first 16 bits for your network ID, which will never change, and the second 16 bits for your host ID, which is dynamic on dialup. Our example IP is a good sample of this--204.64 will never change but 15.48 might.
There are some IPs that are reserved for special purposes, as most of you know. For example, a C class IP address that has a network ID equal to 127 is known as the "loopback interface address"; it allows clients and servers on the same machine to talk to each other. The most common loopback address is 127.0.0.1 Almost all systems call the loopback address with the special name "localhost."
I hope this guide has given you at least a slight grasp on the significance of IP addresses. Look for more articles from me in the future on the subject in which I will go more in depth about it.
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