Understanding Internet Protocol Suite; The Internet Layer

Question

I am trying to understand the Internet Protocol Suite as described by Wikipedia. What is confusing me is the Internet Layer.

So, to see if I understood it, this layer is simply the IP header and data. TCP or UDP or TCMP, or even ARP would be an inner layer the transport layer. So this layer is the IP protocol or IPv4/6.

Granted I understand correctly, would it be possible to have two nested Internet layers? Like an outer layer that has one ip address then another with a different layer like subnet address?

Answer 1

The nice thing about protocol models is that you can invent your own. So I suppose you could create the Craft model that has an extra layer.

But it's hard to see how that layer would function. IP already has a hierarchical mechanism for determining network boundaries. That's what the subnet mask is for.

I would recommend that you don't get too hung up on layers. To quote the Wikipedia article you mention, "The lack of emphasis on layering is a major difference between the IETF and OSI approaches." In other words, it's important that you understand the encapsulation and abstraction function of layers. How many and what they're called is not as important.

Answer 2

I think it's better understood using an example:

Internet Layer manages the addressing. And addressing means to know its own address and the subnet where the system belongs. To be aware of that information it is neccesary to know the subnet mask.

On the internet protocol they go together, because it let the system decides easily if a packet goes to its own subnet or to another one through the default gateway.

Trying to separate it in two different layers is possible but not useful.