How to start writing your own IP protocol?

So my question is, is it possible to write a protocol that does the same thing as an Internet protocol, and if so, how do I get started? And don’t say: “Is the Internet protocol enough?” Yes, it’s just to see if it’s possible: P

I would like to learn a little more about how, just to find out how the protocols are executed. I have some programming experience, but not something like network protocols.