0:00 hello friends today in this video tutorial we are going to learn about open system interconnection model or osi model we will discuss what is osi model the use or purpose of osi model what is osi model layers and we'll discuss seven layer architecture of osi model where each layer having specific functionality to understand the network communication it's very important to clear your concept and understand how osi model work especially if you are working or studying in networking field osi is a reference model for how applications communicate over a network it used to understand how data transfer from one computer to another in computer
0:46 network or across the globe for example there are two computers connected to each other via ethernet cable and rj45 connector sharing data with the help of network card between both computers but if one computer running on macintosh operating system and other one having windows 10 then how these two computers with different operating system are going to communicate to each other to solve this issue and for successful communication between two computers or networks open system interconnection model or osi model was introduced in 1976 the osi model developed by international organization for standardization or simply called iso the purpose of osce
1:34 reference model is to guide technology vendors and developers so their hardware and software can interoperate and define the common framework there are seven layers in osi model from top there is application layer then presentation layer session layer transport layer network layer data link layer and physical layer if you feel difficult to remember osi model layers name and their sequence then try to remember this phrase all people seems to need data processing start from top to bottom a from all means application layer p from people
2:20 means presentation layer s2 session layer t to transport layer and to network layer d to data link layer and p for physical layer so to remember the single phrase you will always remember osi model layers name and their sequence it's very famous face and i hope so many of you already know it osi model is a similar architecture where every layer having his own specific functionality very commonly asked question regarding osc model is which layer is first layer of osa model on top of all application layer or bottom one physical layer to answer this question always remember it's depend on your position
3:06 means you are on sender side or on receiver side see if you are on sender side then top layer of osi model or application layer is your layer 1 because as a sender you will interact or come in touch with application layer first because as a sender when you work on any application like google chrome facebook or yahoo they will use application layer protocols like http https or snmp to send the data but if you are on receiver side then the first osa layer is physical layer because as a receiver you receive data and first layer who interact with data
3:52 is physical layer so your layer one is depend on your location you are on sender side or on the receiver side all the seven layers work together in collaboratively to transfer data from one computer to another computer in the network or across the globe also note each layer having his own protocols to perform his job that will be explained and discussed into another video with details the top three layers application layer presentation layer and session layer are also called software layer because application software like google chrome firefox facebook gmail and file sharing
4:38 application like dropbox protocols are exist and work in application layer the bottom three layers network layer data link layer and physical layer are called hardware layer because network hardware like router switches hub utp cable and rj45 connectors are used in these layers the middle one or transport layer is called backbone of osi model or heart of osi model because it make a connection between top layers or software layers and hardwares or bottom layers now i am trying to explain new osi model layers basic functionality step by step in form of story
5:25 so to understand how osi model work listen and try to remember this story after that story we will unwrap this story and i will explain you osi model in very simple words so let's start it just assume there is one company in qatar and they have seven employees each employee having his own specific task on the top there is ceo of the company and his name is abdul abdul belong to qatar and can speak and understand arabic language only there are another six employees who working in abdul company their names are pintu sakeb tuba noor danish and peter
6:11 the ceo of the company abdul told pintu to send these 400 very important pages to another company name abc and make sure it delivered pin to say okay boss and take 400 pages from abdul and what he found all pages are in arabic language but the abc company in canada they don't know arabic so what pintu did he convert these 400 pages into english first so pinto task is translate the data or input information in a way that receiver and understand it so after converting pin to hand over this 400 pages data to circuit and in form circuit these 400 pages are very important and will be
6:57 sent now to company name abc when circuit receive and check it will go to company name abc in canada so circuit contact to abc company first on his equivalent position person and ask is your company open now they replied yes then circuit circumform there is one document coming to your company from us and when you receive it please confirm us or send acknowledgement that you receive our document they say okay and they both agreed to establish a connection between sender and receiver until they not receive the data so sakip create end-to-end connection between sender and receiver and then hand over this 400 pages to tuba tuba found there is big data file with very important and
7:44 confidential 400 pages so what to buy did she divide these 400 pages into 4 sets of 100 pages or segments and mark these segments as segment 1 segment 2 segment three and segment four because big file take more time to send from one place to another also if they lose that file they lost all data at once but in other hand tuba divide them into small bundle or segment and if one segment lost other data will be safe in other segments after data segmentation tuba send this four bundle to nor no receive four bundles from tuba and write to and from address on each bundle or packet onto
8:31 nor mention receiver or abc company address in canada and on from side she mentioned his company address in qatar also known in form delivery man these are very important papers and co1 urgent to deliver so don't send by a normal post nor instead to take a flight from qatar to canada and deliver by yourself so what basically node did she write to and from address on each packet and decide the route and after that noor sent these packets to dhanish dhanish checked each envelope and found okay documents are also inside on each envelope and sender and receiver address also mentioned on each envelope but all envelopes are open anyone can see and
9:16 read these documents then what danish did he close all envelopes and put seal on it to protect the envelopes so if anyone tried to open those envelopes receiver know that someone tried to temper the documents after this danish hand over this envelope to peter and told peter to send this envelope to abc company in canada peter go to abc company in canada and hand over this envelope to receptionist in abc company receptionist received the delivery and sent to next department that department check all four envelopes are closed and sealed so no one tamper original documents then he open the envelopes and send document to next department next department check the to and from
10:01 addresses and confirm this is his company address and receive the document and sent to next department when next department receives that all four envelopes and they check there are envelope 1 envelope 2 envelope 3 and envelope 4 basically these are one document but in four different envelopes what he did he opened all four envelopes and put 100 pages from envelope 2 to under envelop one pages and envelop three pages under envelop two pages and involve four pages under envelope 3 and make them as a one bundle again of 400 pages and send to next department next department already in touch with
10:47 sender and after getting 400 pages from lower level he confirmed to sender that they received their documents and after confirmation they disconnect the connection and send this 400 pages to upper level after acknowledgment or confirmation the sender responsibility finished and after that receiver higher management take a look on that document or no this is not his problem so what sender did they all did their job that is deliver data from sender to receiver this is full osi model in story if you understand and still remember the story you will easily understand that how osi model work
11:32 so let's start to unwrap the story so first there is abdul in the story as per story abdul gave 400 pages to pintu to send other company abdul means application layer as per osi model and that 400 pages mean any data that user generate or create on application layer and application layer task is to provide interface to user all applications and software we use in daily life like google chrome firefox gmail yahoo or any file sharing application like dropbox that all work with the help of application layer protocols user basically work on applications but
12:18 it include application layer protocols that need to make this application to work correctly in a network or on internet different type of application use different protocol like if you browse something on google chrome or firefox they use http or https protocol for web browsing for email like gmail or yahoo application layer use snmp protocol or if you transfer any file by using any file sharing website like dropbox that time application layer use ftp protocol to make this application to work correctly so as per story abdul give 400 pages to pintu and what pintu did pintu translate
13:03 that pages from arabic to english because into know other companies don't know arabic pintu means presentation layer as per osi model basic function of presentation layer is convert application layer data into machine understandable binary format one and zeros also note presentation layer performing three functions first data translation number two encryption and number three decryption of data so actually presentation layer function is data translation data encryption on sender side and data decryption on receiver end i explain you in simple words what presentation layer actually doing you saw many time there's audio file in your pc for example name song.mp3
13:51 or some document like file.docx or file.pdf if you double click on song.mp3 file where it will be open you will see it will open in mp3 player or if you double click on file.docx you will see it will open on different application like microsoft word or same if you double click on file.pdf it will open in pdf application who telling this where to open this file that dot mp3 or dot tocx or dot pdf extension a link to computer so that extension tell pc which application open this file these extensions basically is the
14:37 translation of application layer input so presentation layer work is how to present data in form of dot mp3 dot t o c x or dot pdf that's why in story pintu translate 400 pages from arabic to english because presentation layer task is present the data after in story pin to send 400 pages data to sakip and sake contact to receiver end and check their availability and establish connection after establish connection succumb inform them we are going to send in data and when you are safe let us know so circuit mean session layer in osa model and session layer task is establish an
15:23 end to end connection between sender and receiver both session layer keep connected until all data not received to other party and if some data loss sender get message from receiver end that data lost or unsuccessful and if receiver and receive all data then session will get reply the data sent successfully that's why session layer also called end to end layer so session layer main task is to ensure that all data received to other party without loss back to story sakip sent this data to tuba what tuba did to what divided 400 pages into 100 pages in small units
16:09 tuba stands for transport layer as per osi model and the basic function of transport layer is divide the data into small units called segments also it control the data flow and error control in data flow control transport layer controls the amount of data being transmitted for example a laptop connected to a youtube server and suppose youtube server can send data at 100 mbps speed but my laptop can process data maximum at 10 mbps speed in that case when i'm downloading file from youtube server and server starts sending data at 75 mbps speed which is greater than the data rate that my laptop can process so by using transport layer my
16:56 laptop send request to server to slow down data transmission rate up to 10 mbps that can maximum handle by my laptop and no data get lost same in reverse case if server is sending data at 5 mbps my laptop tells server to increase the data transmission rate at 10 mbps to maintain system performance also there is two type of protocol in transport layer transmission control protocol or tcp and user datagram protocol or udp to get acknowledgement from receiver after receiving data or need to send any data segment again if data lost between transmission we use tcp protocol
17:42 it's also called connection oriented transmission tcp send data at low speed and re-transmit it again also if some data lost but if you want to send data on fast speed without established session and don't care it received on other side or no in that case we use udb protocol normally wise and video streaming using udp protocol to transmit data so after that transport layer send data segment to network layer as per story tuba sends segment to node and node put the to and from address on each segment and decide the root so the nor mean network layer as power c model and the function of network layer
18:27 is logical addressing routing and path determination of each data unit data unit in the network layer is called packet and this is the osi layer where router exist ipv4 and ipv6 addressing done on network layer and it's called logical addressing the network layer send data in form of packet to data link layer so in the storing nodes and packet to tarnish so danish mean data link layer as proxy model and in reality what data link layer do he add sender and receiver mac address on each packet there are two type of addressing in network logical addressing and physical addressing logical addressing done on network layer
19:13 where sender and receiver ip address are assigned to each segment to form a data packet it also called layer 3 addressing physical addressing are done on data link layer where sender and receiver mac address are assigned to each data packet to form a frame and then send this frame on physical media like copper wire or optical fiber basically data link layer allow upper layer of osi model to access media using technique called framing after that there is physical layer or peter as per story what peter did in story he just sent data frame to receiver and on available media
19:58 so in osi model physical layer convert this binary sequence into signals and transmitted it on local available media it can be electrical signal in case of ethernet lan cable or light signal in case of optical fiber cable so the generated signal on physical layer depends on the type of media used to connect two devices so that's it on sender side as per osi model and when signal reach on receiver and physical layer same process what happened on sender side repeat on the receiver side but in reverse direction like when signal reach physical layer on the receiver side in form of electrical or light signal physical layer convert them into binary
20:45 bits 0 and 1 and send to data link layer data link layer convert them into a frame and forward that frame to network layer network layer check to and from ip address and confirm this is his logical ip address and send these packets to transport layer transport layer receive four packet and convert them into one segment and send that segment to session layer after saving on session layer session will send message to sender that they receive the data or 400 pages as per story and session or connection between sender and receiver disconnected and session let's send this data to presentation layer presentation layer convert data into same format as it send like dot mp3 or dot docx or
21:33 dot pdf format so application can understand the data at application layer and application layer open that data on that specific application so this is very simple and basic intro fosi model in form of story soon i will make video for each layer of oc model and will discuss more technically i hope so you understand our sci model functionality and importance in network thanks for watching my video and please don't forget to like and subscribe my channel
