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Now that we've talked about the TCP/IP suite, let's do a quick review of the different protocols that we will find within the TCP/IP suite. Now, we're not going to go too much in depth on this. We're going to just look at the basic protocols that are there because we're going to look more in depth at these protocols later on as we're doing our packet captures and analysis. Now, each of these protocols is fairly independent. It operates by itself. It performs a unique function that the other protocols don't perform. These protocols can operate at one or more layers. It does not have to be confined to just simply one layer of the TCP/IP Model. So they can work at different layers of the OSI and TCP Models. They also each have defined characteristics. For example, TCP is a connection-based protocol and UDP is a connectionless protocol. That's one example of a characteristic of these protocols. There are others, such as which port they usually operate on and so forth. We'll look at more of these characteristics later as we go. In addition to being independent and working on their own unique functions, they also have to work with each other to ensure complete communications session. Very often one protocol cannot function unless another protocol has already done its job. Now, these are just a few of the many examples we'll look at when we look at TCP/IP protocols. We have, for example, the Hyper Text Transfer Protocol or HTTP. Most of you know that protocol as the one that we use to browse the World-Wide Web with. We also have Simple Mail Transfer Protocol or SMTP, which is used to send email. We also have File Transfer Protocol, which is used to send and receive files between two hosts. Other protocols that we'll find that we'll talk about include TCP, the Transmission Control Protocol and UDP, the User Datagram Protocol. Still yet other protocols are IP, the Internet Protocol, the Internet Control Messaging Protocol and IPSec or IP Security. We'll look at a few more protocols as we go as well in addition to these that we've discussed. This is just a quick look at where you're going to find some of these protocols. Now, let me remind you that this is not all inclusive. There are many more protocols out there that we could talk about, but this just gives you an example of what layer most of these protocols reside at. And by, again, these are by no means conclusive. Now, one thing you'll notice down here at the network access layer where we have ARP and Reverse ARP, some people may say that those work at multiple layers such as the Internet layer and the network access layer and that's true. There's also things that aren't really considered protocols such as Ethernet, Token Ring and FDDI, more physical standards are 802 standards that take place at the Network Access Layer but those aren't really protocols per se. They're more standards. Now, we've seen this picture before in our discussion on the OSI Model, but it does a good job of kind of explaining to you within the framework that we've been talking about about how different protocols can span different layers. Now, again, you could bump the TCP Model against this picture, the OSI Model and match where these protocols take place within the TCP/IP suite itself. But this gives you a good idea of kind of how these protocols work together and span the different models.