What is IP Addressing

What an IP Address Is

An IP address is just that: it's a type of address. It's an address for the different devices that are out on these networks. What it does is it allows traffic to be routed to and from your device to get to other devices and other resources that are out there.

As an example, if you go to a website, what you're doing is you're accessing that website, and that traffic is getting routed to that website via an IP address. It finds that website, and then for that traffic to get back to you, it needs to know your IP address. So IP addresses are used out there in order to locate different resources that are out there on these different networks.

Here's an example of that, where this computer right here has an IP address of 10.41.42.35. Let's say it wants to access some sort of information that's on this laptop right here. Well, this has an IP address as well, so traffic is actually going to be routed across the internet, or whatever networks there are, to this final destination. You have to know what the IP address is of that final destination, and then, based off of whatever information you're requesting, that traffic will get routed back via the IP address for your computer or whatever device that you're using to access that information.

Parts of an IP Address

This is one example of an IP address. IP addresses are usually displayed in decimal format, so as we can see, 192 is just a simple base 10 decimal format, what we're used to working with. However, binary is on the back end of this. What we'll have is each one of these numbers has a range from 0 to 255, because there are eight bits for each one of these sections. You'll notice that there are four sections, or what we call octets. Each one of these is called an octet, and those octets are separated by a period, or a dot. Usually what we do is we'd say that this IP address is 192.168.0.42 — 42, one of my favorite numbers. So this is an IP address right here, and we're going to be taking a more in-depth look into these IP addresses.

If we were to take a look on the back end of this, it would be binary on the back end. These are computers, right? So these are the four octets and placeholders for the different numbers. Notice that there are 32 bits total, and they're broken into eight bits, or we call that a byte. So it's eight bits, or a byte, or really, as I mentioned before, we call them an octet — when we're talking about IP addresses, we call them octets.

So this can be anywhere from eight zeros, which would be zero, to eight ones, which would be 255. There are 256 values for each one of these. Since there are 32 bits total, you can take 2 to the 32nd power and you've got over 4 billion possibilities with that — almost 4.3 billion different combinations.

This is an IPv4 address, by the way. The address range with IPv4 is really quite large; however, because of how we utilize them, we are running out of them and we need to switch to IP version 6. We'll talk more about that here in a little bit.

How IP Addresses Work

This right here is a mapping of a network, so we call this a topology. This shows the topology of a network, or how the network is laid out. On here we have end devices such as computers and possibly a server. We have things like switches here, and these are routers right here, so we have different physical devices. Then we have the internet. The internet is a bunch of different networks all connected together, so often we represent the internet as being a cloud. So this is a network, and how a network is all laid out.

If we want to send a message from one device to another, then what would happen is this would be broken down into a small message that would be sent across the network. In the case of IP addresses and IP addressing, we call this a packet. So this is a packet right here, and it's what's going to be sent from one device to the other.

If we were to take a look at this packet, really what it is, it's a string of ones and zeros that are sent along. In fact, it's a lot of ones and zeros — even for a small packet, it's still a lot of ones and zeros that are sent across here.

Now, this packet needs to be able to be routed through these different networks to the end location, and it needs additional information to do that. So if this is the packet, or the information that needs to be sent, what it will do is add some ones and zeros to the front of this to give it instructions on how to deliver it. We call that the header. So a header goes onto the front of this packet so it can be delivered to the final destination. Keep in mind that with the ones and zeros here, you would probably have a lot more that you're sending across there, and likewise the header gets quite a bit bigger than this also, but this is just representative of how that information goes into the header of a packet in order to make it to its final destination.

Inside the Header

Here is another way of looking at that header. This is an example of a packet — this whole thing that you see right here is a packet, or at least representative of the packet. Really, if we were to dig down deep into this, we'd see a bunch of ones and zeros, and it would just be a string of ones and zeros that are heading across this network. However, for this purpose, this is a visual way of representing this packet.

There's a section of this called the payload. The payload is what we're trying to deliver to the other side. So maybe there's been a request for a web page, and now we need to deliver that web page to the other side. This is that information that's being transferred to the other side, or the payload. It can be anywhere from 0 to over a thousand bytes long.

Then what we need is that information on how it's going to get routed, or where it's going, so it can be routed, so it can be delivered to the other side. That's this header part right here. This header has 20 bytes, so if we were to calculate that out, 20 bytes — a byte is 8 bits — so it'd be 20 times 8, which would be 160. So we have 160 little bits just to tell that packet where to go. Quite a few bits just to tell it where to go, and it could even be bigger than that if there are some options on there.

If we wanted to dig even deeper, this is another way of looking at just the header part of that. This is showing you how the bits would be laid out here. I go much more in depth into this in another class, so I'm not going to get real in depth into it, but if you are interested in seeing what a header looks like and what some of the information in this header is, this is one way of representing that.

What we have across here is each one of these is showing a bit, so you can see one, two, three, four, five, six, seven, eight — so there are eight bits. This shows a byte, then. All across here is four bytes, and this is byte zero through three, so that's the first four bytes. We see that there's a version, an IHL, DSCP, ECN, the total length. So we've got different information explaining what's going to be inside this header and what's going to be inside this packet.

One of the reasons I am showing you this is because we see in here there's a source IP address and a destination IP address. The destination IP address is so it knows how to get to its final destination, where it's going to be routed to. Then the source IP address needs to be in there so that way the information can come back to you. So if you're making a request for a web page, it's going to go to that destination IP address, and when it gets there, that machine is going to put that information that you've requested in the payload and then send it back to you, and it will use that source IP address in order to know where it's going to be sent back to. So that is what you would find inside the header.

In the case of our packet right here, that has some sort of header attached to it, once it gets to this router it's going to be routed to whatever is going to be the best route to get to its final destination. It gets to the second router right here and gets routed again, it gets to this third router and then gets routed to its final destination. What happens within your network operates a little differently, and we're not going to go real in depth into that, but this just shows you where it uses that IP information on these routers to get routed to the proper destination.

Types of Addresses

Before I get into the different types of traffic or different types of addresses, I'm just going to explain briefly what a LAN is. As I mentioned, I'm not going to get real in depth into the differences, or into layer 2 versus layer 3 networks. Just know that this is a LAN — this is a layer 2 network right here. It operates a little differently, but I want to go over how different devices could possibly communicate within this network right here.

So what are the different types of addresses, or different types of traffic? First of all, we have what's called a unicast. A unicast is just going from one device to another device, so this device is talking and the traffic is going to be forwarded directly to another device right here. That's unicast.

The other thing that we have is a broadcast. A broadcast gets sent out, and what a switch will do is send that out to all other devices on the network. So that is a broadcast.

Then we also have a multicast address. A multicast would be that there are just certain devices on your network that say, I want to be part of this group, and then when you send some traffic to that group, just those devices will get that traffic. So that is multicast traffic, or a multicast address.

Hierarchical Addressing

One thing that makes IP addressing so functional is the fact that it's a hierarchical addressing scheme. So what does that mean? The alternative is something like MAC addresses, where things get shipped all around the world and it's really random — and how do you find something when things are all over the place? Versus hierarchical, which has some sort of structure to it. It has top levels, and then it gets broken down further and further.

What does that look like? Here at the top represents everything. This is what we call a quad zero right here, representing everything, and that gets broken down into smaller sections. You can see that it's really wide here, it branches out way out beyond this, but as you can see, this can get broken down into smaller sections, which can get broken down into even smaller sections, which can get broken down into even smaller sections.

Somebody is in charge of this top level, and then it can be sectioned out to where certain people are in charge of the lower side of this, or a subset of this. Then that can be handed out to maybe an internet service provider, so they're in charge of another section of this, and then that ISP can hand out addresses to your specific company. So it's a way to organize — not just being able to hand out these IP addresses and have an organized way of handing them out, but also to organize from a routing perspective, so that way we know where in the world this 12.0.0.0 is supposed to be routed to, because there's a hierarchy to this addressing scheme.

Governance of Addresses

So who's in charge of this addressing scheme? There are actually many organizations. There's a top-level organization, the Internet Assigned Numbers Authority, which is in charge of the overall scoping, and then hands out certain address ranges to these individual organizations that control these big sections of the planet here. From there, these organizations will hand it out to different internet service providers, and the internet service providers will hand out these IP addresses to certain clients. So that is how things are broken down, because there needs to be some governance around this.

Review

We started out by talking about the different components of an IP address: how it uses binary, although most of the time what we see is the decimal form of an IP address, and how it's separated into four octets. Then we talked about how it's used, how it routes traffic from one location to another, how it uses the headers in order to be able to direct that traffic to get to its final destination, and that within that header there is a destination IP address and a source IP address. Then we got into the different types of addresses there are, whether it be unicast, multicast or broadcast addresses. We talked about hierarchical addressing, where we can break down these IP addresses into smaller and smaller chunks and therefore have some sort of organization on how we hand out these IP addresses and how we route these IP addresses and these packets. Finally, we talked about some of the governance that does the handing out of these IP addresses.