hello welcome to web and few this is the first video on the series of networks where we will talk about the exotic model the tcp ip model we will go ahead see the abstraction data flow how they communicate of sale the same level in advance exclusion because I see many times level right now you are watching a video because you are connected to a network that receives zeros one from a communication line that communicates through physical means with a device from another part of the world through a shared protocol neither both parties an architecture of this size is largely complex and this is the reason why there are standards like the cpp subjects that are widely used throughout the world for interconnection said now a little more down to earth there is a need for both devices that want to communicate to use the same version of the same standard to be able to dialogue the difference between the two is that the rosi is a conceptual model it is a theoretical model and has never been realized and implanted in any exhibition while instead you pp is the de facto standard 16 or the one used in industry and in everyday communication and to do what we said before another difference between the moods to the ii that if you had not understood are divided into levels is in how they are organized hierarchically in fact the first four levels are the same for both piles while instead the appeal exorbitant to the last three levels that are condensed into a single level I called it application in the pilatti si pia and pizze this generates a bit of confusion because even iso osi level that is called application however is always condensed in the sails production given that we have read that models are physical and that the one used the t si va p now let's proceed with that we do now let me in the protocols on what they are what they are used for and for the caci enter with our models the definition of protocol is the set of rules that allow two homogeneous devices to communicate you can find many details on the protocols we will go into more detail in an opposite playlist what we are interested in knowing for now is that they provide communication between homogeneous entities or at the same level the idea is precisely that each level to its protocols and each level establishes a connection with another device with the same model its on its same level with its own protocol here if you want we can't fire an http request in the network cable there is a need for a little more elegance if you want an example it is as if the level were the continent and the protocol were the language if the invasion of the same now we have arrived at the crux of the matter or rather why the stack in this case tcp ip is divided the levels because Nordic understand this there is neither from the rapid this concept several abstract however therefore let's proceed with an example that drawn the blackboard suppose that you are your computer connected to the wifi and take the loading of this youtube page with this video as an example therefore on the left there will be you with your computer that you are committing to see the video and on the right there will be the youtube server for you in this case cdp miche but it was not a request that tdp towards youtube server and serves of but did not respond and containing the page containing the video and then it does not work like this however they assume that the video does not start you allows play your computer but would not have asked for the first storm of the video and server responds with the buffer of the video then go ahead and watch it you like the video request another automatically to the server it answers you in other words as if you want to open a communication with the youtube server where there is a question and answer dialogue this is allowed in gissi and psp in fact its main objective is to put in communication of two levels of two separate physical entities or this application level that you are connected in this level while instead the packets will not do so but will go down to the physical level they will go in the transmission medium they will be transmitted I should move up to the physical level of the other server and they will go up the application level while instead it seems that you are dialoguing there from ours going back to the beginning you have opened the browser so 7 at the application level write the link in the browser bar press enter and the browser proceeds to form an http request for the video that you have put in the bar through the http protocol which we can conclude is an application level protocol since used in that level the request towards is not sent to the other side because it must go down the whole stack and the physical level physically light requests and one on the transmission medium we will now do something called encapsulation now it seems to me a good time to say that each layer sees the data it handles as a sort of envelope the analogy is quite accurate from a very good mind model if we look at it here the application layer of your device level 5 takes the links you want to see with ovens it is not asked for http and closes it in a level 5 envelope now the level 5 envelope can only be opened by another level 5 device op itself or another device on a server or anywhere else but it must serve the lucini as level 3 it cannot for the bust at level 5 and that is why each level has a particular name for its envelope now the goal of our application layer is to have this level 5 envelope at the application layer of the server edition we cannot send it directly so we make it go down a level the transport layer receives from above an envelope in level 5 the transport layer takes care of congestion and it is tcp protocol which we will see that it does not have information to add it cannot have from buster level 5 but then it writes information on a sheet of level 4 I put it together with the level 5 envelope in a level 4 package it seals it and passes it under the network level 3 the network level goes the same thing takes because it has information from ginger commissions rizzi b hangs puts together the two level 4 envelopes and the information he wrote of level created closes them in a level 3 display and does the same thing at level 3 at level 2 up to level 1 level 1 once it creates the level 1 envelope that contains places at level 2 plus information level 1 it can no longer lower it down because thank God the levels have run out and so at this point it converts it into a series uni and transmits it on the transmission medium until it is received on the other side of the other physical level of the other device this stack will do the same thing but in reverse or in fact I'm left with the level 1 envelope here I read the level 1 formations check for him recipient pass to place level where above it shows level 2 open veins information level 2 so up to level 4 milan 4 reads on information check if it's right and they pass to your level 5 application level application level take it pages the server puts it in a new level 5 envelope of response it 's all procession done again this virtually as if a connection was established between the two highest levels between the various applications of our positives because in effect envelopes are sent then they are passed up and down by many levels however it is as if all the effects were talking to each other from this extremely detailed example we can extract some considerations that are valid in general the physical level and the one that gets its hands dirtiest because it has the task of transmitting the bits of the envelope that encapsulates all the other envelopes in signals to the transmission medium level 2 is the same level at which the switches arrive and is responsible for managing the mac addresses they call on envelopes the epos level two frames level 3 at the network level and the same one where the routers live and is responsible for managing the ip addresses in concrete on an incoming packet to verify that the ip address with kisses that of the local machine and to send it up or if outgoing packet to insert the ip address of the recipient and of send it to a lower level now there is an observation that makes you understand a lot of things level 3 deals with IP addresses this is not the observation level 5 deals with applicative things at this point the levels above level 3 are not interested in knowing how the addresses work because level 3 deals with managing and making everything that concerns IP addresses work consequently it is not always like this in general however in the level 5 request there is no recipient IP address because it is something that level 3 deals with the whole stack is built on this assumption namely that the lower level deals with the thing for which it was designed and higher levels can use it without problems that thing will be taken in charge and they deal with things a little more abstract in fact bytes can be sent almost a cuddly addresses however the interface therefore physical things here are ritual addresses that are more abstract here are practical congestion and things a little spoilery the list is instead five they are more applicative things therefore like a browser the management of web pages or requests http https smtp whatever you want the level 4 at the tcp level it deals with network traffic management of congestion mitigation and sending packet flows and uses the tcp vdp protocols the worst veil and the highest one and is designed specifically to be closer to the user therefore to a lot of protocols and precisely by sitting on 4 layers of abstraction it can do very different things including smtp or little send mail est http https farelli di aster http https for websites or internet time igp uses ssh to make remote shell sessions uses ftp to transfer files used many protocols there is one last one to remember that I put here just so that we are all synchronized on the same page a level does not necessarily know what is above it whatever it is at least of protocol violation and if a packet arrives in reception the salt the level must go up while instead on a packet is sent to any level the level that receives it to send it back down or for example network level sometimes discards the packets are received by chance or if they are not addressed to the machine that received them and a note said this I would say that we have finished what there was to say about the expensive tcp ip protocol I warned them and so we will see each other in the next video if you have any questions and do not give up in the comments if I refuse the video put the like and we will see each other