So, ARPANET eventually evolved into NSFNET not too quickly after ARPANET started, but let's look at some more of a time line here. 1974 TCP and IP TCP stands for transmission control protocol. IP stands for internet protocol. that was really invented in 1974, and that was invented by Robert Kahn and Vinton Cerf. And TCP/IP really is the foundation for the modern internet, and even though many of the other parts of the internet have changed quite a bit TCP/IP has remained relatively unchanged even from back when it was invented. so we'll talk about IP in this chapter, TCP deals more with end-to-end connectivity and we'll talk about that in the next lecture. so a protocol is a language for devices, so each of these, TC, Transmission Control is a protocol and the internet is a protocol. And so it's really a language that devices speak so that they all understand and they're all, they all know kind of what to read in the messages as they're sending them across. And so that's the idea of protocol very important to understand. and TCP/IP is really a very scalable way to connect hosts. And, what we mean by scalability, and this will become evident as we talk more about the Internet, but is that you can add more, and more, and more hosts to the network, and it'll remain TCP/IP won't have to be changed, right. So, you don't have to change the protocol when you add more people to the network, which is a very, very good thing. Thing about TCP/IP. it became part of the internet not until 1983, actually. So ARPANET had a previous scheme that they used, and in 1983 became part of the internet, when ARPANET was still around, but it had actually already become a subset of the quote, unquote, internet. So, 1985, 1995. the National Science Foundation took over the development of the Internet really and then NSFNET came out. And it was an Academic research network. Part of the reason the NSFNET came out, actually, was because under ARPANET it was very hard. It was a very tightly controlled and regulated, so it was really hard to actually buy into the ARPANET if you wanted to add a host. So, NSFNET, they came out and said okay, well as long as you're doing academic research you can add a hub onto this network. and it wasn't until the 1990s actually that you were allowed to do anything with commercial ventures on the Internet. so they did allow, for instance, companies to have who used the internet, but only as it was related to research. Right, so you could obviously you know share files with other companies to do research related activities. It wasn't until the until much later that we were able to do things for fun and entertainment on the internet. It was originally just for purely for research. And so this NSFNET had the idea, it was really a three tiered structure. This was when it came out, and that extends really to the modern day, even though they're not called these anymore. At the lowest end, we had campus networks, right. They're, they're so, that's how you know, your it, your, whatever campuses run NSFNET at this time would be at the lowest level. they would all be connected in what's called, to a regional network, which is one step above. And then, the entire backbone would connect the entire thing together. So it's really kind of a tree structure, right? Where this is the roots and it comes out to the leaves. That you can say the campus networks really form the leaves of that tree. and so this is the idea, this is that three tiered structure campus, regional, and backbone. so the backbone by 1991 already had 14 nodes. Just to give you an idea of how large it had become, even by then. The the backbone notes are showing up at the top here. they're all showing and connected. And then at the bottom, these are either a regional or a campus-level nodes. So, you can see how many nodes there were. It really extended, not always the United States, but also, abroad, to even different countries as well by 1991.
