The most common layer in the stack

This might feel redundant at this point, but it really is worth driving home that the application layer is where the vast majority of .NET developers are going to be doing their network programming. Since that accounts for most of you, we're going to keep talking about it. But why is the application layer so important?

The crux of it is that the application layer serves as the gateway to network activities for your business logic. This becomes very apparent as you explore how thoroughly .NET has hidden the implementation details of any of the responsibilities of lower levels of the network stack. Essentially, if there is something that you need to specify about how your application should behave anywhere below the stack, you'll be doing so through a .NET library class.

I really can't stress enough how important it is to understand how the protocols behave under the hood. Knowing how the libraries are implemented will leave you better equipped to actually use them in the future. It's like learning to drive a stick shift. If you only ever learn the steps you have to perform to change gears, you'll likely get rusty without consistent practice. Over time, you'll have forgotten enough to not be able to drive a manual transmission anymore. However, if you learn how the steps you take serve to allow your car to drive, you'll never forget the steps themselves. Even if it's been years since you last drove a stick shift, you'll be able to reconstruct the steps you need to execute based on your understanding of what those steps actually accomplish. By this same measure, understanding exactly what the .NET core libraries are doing for you will enable you to use them more efficiently and correctly. You'll find yourself looking up the documentation less frequently and be better able to find the methods or properties you need through IntelliSense. That said, let's look closely at some of the most common protocols in the most common network layer.