Understanding the TCP/IP protocol, Part 1

WindowsNetworking.com - Quite a few system administrators I am sure, are familiar with the TCP/IP protocol suite. By extension, many of us are also used to looking at packets composed of both the TCP ( Transmission Control Protocol) and IP (Internet Protocol) protocols.
A large amount of traffic have both of them in it, so they could be considered joined at the hip for lack of a better term. Thus the bulk of the Internet traffic that we see today is largely composed of both TCP and IP ferrying around whatever application layer protocol they may be carrying. That being said, as many of us remember, the computer world is not all just composed of application layer protocols, and the aforementioned TCP and IP protocols carrying them around. This three-part article will convey to you exactly what is going on in both the TCP and IP header.
There are quite a few other protocols that don't reside at the application, transport, or networking layer. While you may be asking yourself "why the devil is he talking about the OSI reference model, is this article not about protocols!?" Well, simply put, using the OSI reference model as our template will give us a great way to map protocols to specific layers. In essence, it allows us to give some order to what can quickly become an unwieldy beast; the understanding of computer-to-computer communications.
Think of it this way, using the skeletal outline of the OSI model, we can add bits and pieces to it allowing us to flesh it out. It really simplifies our lives as networking professionals if we use the OSI reference model in such a fashion.
Bring on the gory details!
Any system administrators reading this article are probably familiar with the tool ethereal. This tool breaks down the contents of a packet for you and maps all of the hex values found in them. Not only that, but it will also tell the name of these values. What values you ask? Good question! Values such as win size, ttl values, and mss amongst others. These terms may seem a little cryptic to you right now, but rest assured you will understand them shortly. You must understand these types of details in order to gain a deep understanding of TCP/IP.
Explaining such difficult concepts as the minutiae of TCP/IP can be a difficult task, not to mention the reader trying to grasp all of the dry text. With that in mind I always strive to give some visual cues. This