Lecture OSI and TCP/IP Models

so like I was telling you guys the OSI model is more of a reference a guideline to help us delegate responsibilities to help us understand what the communication process entails and so I had you guys just list them out from top to bottom but remember the communication process entails both directions going down the stack is what we call encapsulating and going up the stack we call decapsulation and today I hold to explain why the encapsulation process is very critical to the communication that is to get the message from the sender to the receiver layer 6 sorry layer 7 layers six and layer 5 can be grouped in in fact the sole responsibility for the three of these is to reduce what for the transport layer yeah so by time we get down to the transport layer the PDU should look something like this it should be in a binary format so these three layers produce apdu that we will call data PDU short for what protocol data unit depending on the application all the encryptions through the compressions these zeros and ones are going to be something that's really trivial I mean that's what Network people see all the time or just zeros and ones they don't know if it's an email or it's a voice communication or whether it's a video stream in fact that's what we call the converging network right the digital converging network this is why Time Warner and all the other companies can offer you phone internet TV on the same line it's all zeros and ones once you get into zeros and ones you need to identify that typically on the application layer we identify zeros and ones by a file extension a dot exe represent zeros and ones use to execute instructions a dot JPEG jpg represents those zeros wants to display a picture or color right likewise we have identification used in networking sometimes we call these addresses to identify the application of the service that's the first thing at the transport layer is going to do the transport layer is going to identify what applications making the request and what applets are what service is going to receive this applications make request services receive them all right so way we identify them is to report addresses it's going to be a source and there's going to be a destination we stamp each and every one of the PDU for the transport layer with the source and destination what is the PD you call to the transport layer segment and why is it called a segment because what is the second thing or I should say technically this would be the first thing yeah it takes the date and breaks it up into pieces and so we call this piece of segments right so the PDU for the transport layer it's called a segment why do we segment our data security performance and we can also allow multiple communications to occur relatively at the same time which we call multiplexing right what was the one of the protocols that defined the segment because remember protocol data unit right so if we're producing apdu there's got to be a protocol that told me how to produce that PDU correct so what was one of the protocols TCP was one of them absolutely and TCP we said time irrelevant I'm going to sacrifice time over reliability okay this is why those big fat Cadillacs have a bunch of luxury items in there that add weight to the car but a sports car or is going to cost more than a Cadillac I mean if you're getting like a high-end sports car probably going to trim all that fat because they want speed correct so what was the other protocol designed UDP TCP is the most popular one all right we passed that segment down to the network layer and what is that Network layer going to produce what are we going to take that segment and make it into a packet and what is one of the most popular protocols on this layer that tells the operating system how to take a segment and make it into a packet IP and with IP we have a source and a destination address much much bigger than port addresses but nevertheless same principle but what's the difference between these addresses what does the transport layer use addresses for they're both logical but which one does the Trant what does the transport layer use addresses for to identify what they're called port addresses but where they use to identify services or applications because we look above the transport layer the transport layer is looking up it says ok who's getting this data who's getting that data the way they know that is through port addresses okay so what are the addresses used at the network layer what are they used to identify the key is network was the definition of a network for more devices connected together so they get identify the devices on the network so the sender and the receivers IP address goes here into the packet alright so the fact it gets passed down and that becomes what so we're in a data link layer and we're going to produce what we call a frame member the frame is the only time we add a header and a trailer and that frame uses well we could use all kinds of different protocols I always like to talk to data link layer with the physical layer because it's ideas to connect all that logical stuff now the way I explained to my last class they got a kick out of it but I think it clicked can you guys tell me what Internet Explorer Internet Explorer smells like I know you guys gonna say oh it smells like piece of but what about Firefox what about Chrome what do they smell like what do they feel like when you guys touch Internet Explorer what does it feel like felt a little heavy squishy it doesn't have a smell it doesn't have texture because it's all virtual it's abstract right if I tell you what a9 but if I ask you with a 9-volt battery feels like you guys can tell me right that's down here the physical stuff is what we touch what we work with so this layer is to take that abstract stuff and make it into something real and we need standards we need standards that tell me ok I can work with all that logical stuff give me all those zeros and ones and I'm going to convert into something that people can touch taste here feel sorry see all depends on your interface card now I say here because if you could hear like my dog or beyond you can hear the Wi-Fi network sending messages and they operate a 2.4 gigahertz spectrum that's well beyond our hearing and you guys are going to be glad for that I mean the way we listen to FM radios which are in the megahertz is you need a tuner to tune into that frequency than to tone it down to a range that you can hear correct networks we call them modems but nevertheless those signals are all over us they're in this class from all time I'm sending one from this microphone to my phone it drives me nuts if you guys heard or saw all those things but they do exist the question is how do I know that the interface card that I bought is going to work with my other devices on my network there's got to be standards like when you go shopping for a hard drive it says USB or a flash drive says USB you know you have a USB port and you expect it to work so when you guys go shopping for interface cards or network devices what are you looking for when you guys go shopping for Wireless cards or wireless routers what do you look for says Wi-Fi maybe but more importantly since 802 11 followed by a letter so we're latest one is 802 11 AC in order to use all that bandwidth to use that wireless router to its full potential what kind of interface card are you going to need an 802 11 AC interface card so don't stop halfway and buy just a wireless router go the extra mile by the interface card that uses the full potential out of that wireless router clear about that if I was setting up a wired network like we've been doing a packet tracer you click on the computer it says what for the interface card fast ethernet and that is a protocol or a standard that happens right here the datalink Ethernet as source and destination addresses but they're physical that means the company that made that interface card burned an address into that card that you cannot change we'll get more into the difference between physical and logical all right physical just takes those bits and produces a signal to carry them that's it now I tell my students there are other models that explain the same process some are less elaborate as this one of the most popular models that we use as a substitute to the OSI model is called the TCP / IP model and if I want to take a guess why it's called TCP / IP because the persons that develop the internet focus on two protocols and only two protocols TCP / IP they need to make sure that data was reliable because went back when it was called ARPANET everything was very sensitive with all this research there wasn't any like voice or video any of that kind of crap that the reason why the internet was developed was because a cold war situation that we connected our missile silos so when Washington DC was attacked we can still give the launch codes over in Alaska or Turkey or wherever so we had developed a very reliable network so if pathway gets disconnected we have another way to get there another route and that's what IP says so they said you know what we developed this thing let's create a model that shows a grand overview of how this behaves and they said in order to use our network if you want to send a web page you're going to a web browser and so they said the first three layers are going to be accomplished under the application layer I just grouped the first three in fact when we looked at layer seven six and five didn't I say that's all software stuff OSI models a little bit more thorough and said you know what I don't want a katana fer writing the user interface for my web browser and thank God for that because if the cryptographer did do that they would hide the okay button it's a secret likewise I wouldn't want a programmer who develops user interfaces to write the cryptography program because they would say oh it's real easy passwords password because their job is to make the application user-friendly the cryptographers job is to make it very unfriendly so that when you see it it doesn't make any sense very thorough and so what I like to see is does that happen over here absolutely so there's like a division and probably in that division there are these departments because they need to be accomplished we do need session stuff we do need presentation stuff but TCP was like yeah that's all in the software and that's we're going to do and it too will produce data and it too is interconnected and it's going to connect to the transport layer and it too would produce segments because I don't care how you communicate but eventually in your communication process you're going to need to identify what you're talking about the subject right you ever talk to somebody than out of the blue they bring something up you're like we were just talking about a hell on wheels why are you talking about the weather next week wouldn't have anything to do with the topic right so in there you need some way to identify what application or what service you're talking with so transport layer transport layer all the same remember these are the people that developed the Internet so their lair isn't going to be called the network layer rather they're going to call it the inner network layer and what does inner mean anyway enter its just abbreviated from interconnected so just a bunch of networks connected together that's networks are networks whether they're jump together not they all need to behave the same way and it too is going to produce a packet all right there's a very simple model so it's going to take the last two and group them together and they're going to call this the network access layer and oh hell does that cause problems so for I have a ninety nine percent failure rate on my exam when I give a multiple-choice question and I say Oh which layer on the OSI model is the same as the network access layer and I will only give you one it'll be like network layer network transport in session something like that and students want to say this one network network it's got to be the same thing and it's not here is access going on to the network we're talking about the physical stuff so it takes both the data link and the physical stuff in here and it - cause it's PDU a frame now let me give you an example away from networks into hardware because I'm a hardware guy I love reading hardware magazines I love staying on latest edge with CPUs GPUs and all that stuff specially this stuff with the phones like iPhone just released a new processor they call their motion processor and I'm just like oh well just another process of great what does it do and so I'm looking at this and I remember back in the 90s you know you get into little geek fights and say oh and video is better than ATI or some crap like that and then somebody said well no H it's got great processors and their GPUs are excellent they have more transistors and they have more shaders and everything and I'm like oh yeah whipty-doo and just like you guys might be getting a pissing contest with about xbox360 versus the PlayStation 3 oh yeah PlayStation 3 has a lot of muscle compared to the Xbox but what drives us to these game consoles content likewise I was so discouraged with ATI because they had shitty developers the people that developed drivers didn't know what they were doing because Hg I needed to save money so they said you know what you're an engineer you're also going to develop the driver what is a software driver it acts as a translator between the hardware and the operating system right if your translator isn't doing a good job translating you can find yourself in prison right likewise if your driver isn't using the hardware to its full potential you wasted all your money on all that muscle and what you have is a dumb jock I can't read and so you've paid a millions of dollars to play football well you guys understand the game plan and so now he's running to the opposite field goal or run to the opposite end zone and you're like well you're big and strong when you're pretty stupid so I'm gonna get rid of you don't bring out any teams I kept it loose likewise so what happened is over here and Vidya decided to follow a model like this and said we'll pay for engineers we'll also pay for software developers that do nothing but develop drivers you need them but they just have more levels which might cost them more but hopefully they produce a better product over here the same process has to be done the communication process has to happen however how we group women organize or delegate responsibilities is our business model

Channel: Nicholas Andre

Views: 123,469

Rating: 4.9334297 out of 5

Keywords: Internet Protocol Suite (Internet Protocol), OSI Model (Literature Subject), CCNA, Cisco, Nicholas Andre, Your @Home Instructor, Networking

Id: Pje0l5r7_lk

Length: 19min 30sec (1170 seconds)

Published: Thu Sep 12 2013