[MUSIC] So this lecture we'll talk a little bit about the internet and structure and we'll get into internet protocols. Protocols in general. We'll talk about what a network protocol is. We have to know a little bit about these. We don't want to go into detail in protocols. But you have to know they exist because the hardware that we buy when we make our IOT device, the hardware that we buy, we'll buy it matching a particular protocol. So we'll pick the protocol and pick the hardware to match that. So we need to know at least the existence of protocols and what they are. So, internet structure is ad hoc, that is, it's very irregular, right? People can join the network, leave the network. I can open up a laptop in this room right now and suddenly it will be part of the internet, right, and people can send messages to it. And then if I shut if off, it is now temporarily no longer part of the network. So, the internet is very dynamic. Somebody can build up a new network right now, plug it into the wall, and bam, there's a new addition to the internet, and that happens all the time. It has an unpredictable structure, but it still has to work. Actually, it's pretty amazing that it works as well as it does, given the fact that it's so crazy. So it can be changed by anyone at any time, so you have to be able to send messages between this wide variety of network types, right. So you've got these LANs that maybe use different protocols, routers that are speaking different protocols, destination LAN, it speaks a different protocol. And so you've got this, you've got to be able to consistently send messages regardless of everything else. That means if I set up a host in my office, I set up a network in my office, that thing has got to be able to talk to some LAN on the other side of the world without knowing anything about the protocol of that LAN. Right? And without knowing only minimal about it, right? I don't know what type of protocol they're gonna use on that LAN. All I know is I wanna send a message to a machine on that LAN, right? So you have very little structure, but you still have to have some level of uniformity so that everybody can talk. So how is it possible to send bits, bits meaning messages, across these networks hop to hop through these different networks with different sort of different protocols essentially. So, we'll talk about these protocols, let's define them. Protocols are basically a set of rules, rules of communication. If we're talking about for network protocols it's a set of rules of communication. And there are a lot of rules. But generally, it's a set of rules, hopefully a minimal set of rules, which as long as everybody adheres to those rules. Everybody can communicate, okay? And you wanna make these rules minimal so that they're not a burden on the local area network. So you wanna give people who are building their local area networks as much freedom as you can as to how they design their network. But there have to be some protocol rules that they adhere to, some minimal rules which will allow them to communicate with all the other local area networks. Through the internet. So the internet has protocols associated with it, which if you wanna talk on the internet, your networks have to support these protocols. Now just to give you some intuition about what a protocol is, it's basically something that you add. It usually involves adding data to a method. Okay, regular type of data to a message. So if you ever watch old movies, or cop movies, something like that and they're on the radio, and they say something. Something something something over, right. Over, they say over at the end of their message right? And as soon as they say over, somebody else can start talking. Right? And then when they're done they just say over and out, right? So this is a protocol. Cuz what it says is that every time you send a message, I don't care what the content is, I don't care what the words are. Just make sure that at the end of that message you say the word over, right? And no matter what the content of the entire conversation was, just make sure that at the end of that conversation you say over and out. As long as you follow those rules, everybody can talk. Because the goal of those protocols is, the radio protocols with humans talking on radio, is so that two people aren't talking over each other, right. You want to make sure that one person's talking at a time. So whoever is talking can keep talking until they say the word over. When they say that, the other person knows oh, now it's my turn, and they talk until they say over. So over's like passing the baton to the other person to talk. And as long as you adhere to those simple rules, it doesn't matter what you say, what the content is, you can talk with somebody else. Now there are limits to that, right, because there's no rule about how long you can talk before you say, over. So you could just talk all day and then finally say, over, and then you would be a bottleneck to the network and that would be a problem. So internet access has rules to handle that, right. There are time limits and things like this. But you get the idea. A protocol is basically extra data that you add, is represented by extra data you add to the message, like the word over or the word over and out. Right. There all kinds of rules that extra data that you put in there that are used to enable communication. So we call those, that a protocol, that's a set of rules that enables communication which minimally constrains the message. It adds a little bit of data to the message typically. That's what a protocol is, and TCP/IP is the most common set of protocols for internet. In fact specifically IP stands for Internet Protocol and if you're using the internet, if you want your machine to talk on the internet, they have to use Internet Protocol. They have to adhere to the rules of IP. Now TCP/IP TCP is another protocol and that protocol is, it also is used in conjunction with the internet. So if you use the internet you're either using TCP or UDP, right? And you're using IP. So I said TCP/IP it could also be UCP, UDP/IP. A Universal Datagram Packet, if I recall. Protocol, sorry. And IP. You put those together and that's internet. So you can do anything else you want, you can add all kinds of other data into the message. As long as you adhere to those protocols, you can talk on the internet and your machines can communicate with other machines on the internet. Thank you. [MUSIC]
