Networking 101- The Basics of Protocols

hello my name is David Bromley in this video we're going to look at the very basics of networking in particular we'll cover network protocols protocol layering and the suite of internet protocols tcp/ip I'll give it really just a high-level overview of how they work so computers are connected these days via networks so we have here a computer let's call it a B C and D and what I've represented here by these arrows is computer network links now the computer network links are just the ways the computer can talk and these may be via wires over wired protocols like Ethernet or over the air via protocols like 802 dot 11 now the goal of these networks of course is to enable these computers to talk and in particular they're going to send messages back and forth now these messages are often called packets so a packet is really just another word for a type of message the computers are passing back and forth now computers are going to exchange these messages but of course computers only do what they're programmed to do and the way we program computers to pass messages so that the message descends is the message B can read is via protocols protocols specify how and when a computer should talk and how it should respond when being spoken to so as an analogy let's think of protocols that humans follow for example if we have Alice and Bob here in Bob sense says hi to Alice a common protocol is well of course Alice has to say hi back and then a Bob follows up with I have a question then Alice of course is going to as part of you know the normal protocol of people talking saying what is it and then Bob would of course ask his question and so really this protocol is just a set of conventions that people agree to now humans agree to these protocols implicitly it's just part of our social culture on how we go about talking computers of course we have to program with specific protocols so in particular we're going to focus in this lecture on network protocols which are just the set of rules governing the exchange of data between computers so recall that computers are going to be passing messages which are also sometimes called packets now the protocols themselves define all aspects of this communication for example there are protocols that dictate how one computer will find another computer for example we have computers a in B here maybe B is Google comm and a is your home computer when your home computer wants to find Google comm it has to look it up by name and in particular it has to look up what it's what's called IP address this is its Internet Protocol address this is really just how the computer would reference this particular computer B as opposed to using this name Google com there's also protocols for how data is sent back and forth for example when they want to send packets back and forth there has to be a message but there may also be data that includes for example the sender and the recipient and of course for specific applications like say HTTP there may be special formatting that has to apply there for example in HTTP there's a message called get and what get means is well of course get a particular webpage now when you submit a form there's actually a separate message type called post that submits the form data and so part of the HTTP protocol defines how getting a page work and how posting a form works one of the cool things about protocols is they can be layered or stacked and I've shown here a common set of protocol stacks at the very bottom of the stack is what's called the network layer and examples of this or things like Ethernet now Ethernet is a type of wire of course but it's also a protocols and it's the wire that it's the type of protocol that transmits over that wire or for example Ethernet is also used in 802 11 now this provides a really kind of a low-level protocol that specifies how packets should be formatted on the physical wires of the physical medium like the wireless network above that lays lies the internet layer and in the internet layer are things like the IP protocol which specify this for example the source address and the destination address of hosts on the Internet above that is the host to host transport layer in two of the classic protocols is well the first one is called user Datagram protocol which is a very simple protocol used to send packets between a and B it provides no reliability guarantees and it's it's really kind of the simplest protocol you can think of as well as one called TCP or the stands for transport control protocol and this is a more advanced protocol that provides for example reliability and other features now these are really the the such basic protocols in on the internet that collectively they're called tcp/ip and they're ubiquitous on the Internet most communication is going to use tcp/ip and in future videos when we look at Wireshark we'll actually look at some of the data inside these package packets above tcp/ip our specific application layer protocols for example one would be HTTP or hypertext Transfer Protocol which is of course used on the web now I mention these protocols can be layered and the way they're actually layered is in a sense it's like embedding so we have here as I mentioned the Ethernet protocol which is a very low-level protocol and it has an Ethernet header that specifies kind of like at the wire level the source and destination address and then it has room for data now in that data is where we put the next higher level protocol so this fits inside this region right here so this IP message or this IP packet is the data of an Ethernet packet and of course this has an IP header and it has some IP data and as I mentioned the IP header includes things like the source and destination address and inside the data of it could be for example a UDP header and on top of UDP is an application layer message for example DNS now here's just another example of layered protocols and this one I've given is for HTTP and I'm going to go at it instead of from the bottom up I'm going to go from the top down now an HTTP there could be a very long message that you want to send for example this could be an entire web page which may be kilobytes in size now this web page gets chunked up into individual packets and each packet I should have drawn my lines here a little bit more carefully each packet each chunk of data gets sent in a packet and each one of these packets for example an HTTP is sent over the TCP protocol and the TCP protocol is layered on top of the IP protocol and the IP protocol is layered on top of the Ethernet protocol so in this lecture we covered a couple different things we talked about network protocols and network protocols are really just a convention for computers to communicate information and data we talked about protocol layering how protocols can lie on top of one another and I described the tcp/ip suite and give examples for example I talked about DNS going on top of UDP going on top of IP going on top of Ethernet and I talked about HTTP being on top of TCP being on top of IP being on top of Ethernet so that's a really quick introduction you should go read of course other resources to get a more in-depth view but I hope this give you a high-level idea of how things work until next time always keep hacking

Channel: Pico Cetef

Views: 113,913

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Id: ISrJ5ojvOgA

Length: 9min 22sec (562 seconds)

Published: Thu Apr 25 2013