OSI Model Explained | Real World Example

welcome to surf pros in this video we're going to be taking a look at the OSI model so what is the OSI model the model is a theoretical stack of seven layers that can be used as a reference to help understand how networks operate the model was introduced to standardize networks in a way that allowed multi vendor systems prior to this you will only be able to have a one vendor network because the devices from one vendor couldn't communicate with others it's worth noting at this point that we don't actually use the OSI model we use something called the tcp/ip model the concepts are exactly the same the layers are slightly different so if we don't use the OSI model why would we bother learning it well that's because it still referenced a lot when troubleshooting or describing network operations let's take a look at the layers starting from the bottom up layer one is the physical layer the physical layer is the lowest layer of the OSI model it's key responsibility is to carry the data across physical Hardware such as Ethernet cables layer two is the data link layer at this layer the physical addresses are added to the data this is the source and destination MAC addresses switches are located at this layer the network layer handles IP addressing and routing at this stage of the OSI model the source and destination IP address are added reuters operate on this layer therefore the transport the transport layer of the OSI model adds the transport protocols such as TCP and UDP TCP for example is used for error handling and sequencing to ensure no data is lost this layer also adds the source and destination port numbers layer 5 session this layer is responsible for establishing and terminating connections between devices layer 6 presentation this layer formats the data in a way the receiving application can understand it this layer is also able to encrypt and decrypt data if needed layer 7 application this layer is where the application and user communicates application specific protocols are used here such as SMTP if you're sending an email for example a really good way to remember these layers is simply all people seem to need data processing a PS T and DP so to fully understand how this model works you need to see a real-world example let's say you send an email the data travels through the OSI model adding and processing data on each layer and this process is called encapsulation step one the application layer our load creates the data the email you wrote the email addresses etc etc and gets ready to send it using SMTP which is the Simple Mail Transfer Protocol step 2 presentation there the data is formatted in a way the receiving device will understand in this example probably a SC III this layer could also encrypt the data if needed step3 session layer a session with receiving mail server is started step for transport this is where it decides to use TCP or UDP in this case we'll use TCP to make sure every packet gets delivered also the source and destination port is added to the data step 5 Network the IP address of the mail server is added as the destination and the source IP address is also added through the data step 6 data link the MAC address of the router and the source MAC address of the host is added to the data step 7 physical the data is sent out on the network using Ethernet so when the data reaches the other side the receiving device will process the data in the same way but in Reverse starting from the bottom up okay so that's the OSI model but how can we use this to troubleshoot you may have heard the term or that's a layer 2 problem or sounds like a layer 3 issue when you hear that that's people referring to this model let's say there's a problem with the network if we go through this model checking every layer we can soon diagnose the problem for example layer 1 or the cables plugged in is the network card functioning could it be a faulty cable layer 2 maybe the switch has gone bad layer 3 is the route to functioning do I have the right IP address and the process goes on and on from there I hope you've enjoyed this video if you have remember to subscribe comment and give a thumbs up thank you for watching you

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Keywords: osi model, osi model explained, osi, osi tcp/ip, how does the osi model work, cisco, ccent, ccna, osi model works, how does the osi, Engineering Mentor, OSI Model, OSI Reference Model, Communication Model, Computer Networks, OSI model layers, iso osi model, 7 layers of OSI

Id: LANW3m7UgWs

Length: 6min 8sec (368 seconds)

Published: Wed Sep 28 2016