OSI Model Explained | Real World Example

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The OSI Model Explained

What Is this OSI Model?

The OSI model (Open System Interconnect) is a theoretical stack of 7 layers that can be used as a reference to understand how a network operates. The model was introduced to standardize networks in a way that allowed multi-vendor systems, prior to this you would only be able to have a one vendor network as the devices could not communicate with other vendor devices.

The Layers

Application (layer 7)

This layer is where the application and user communicates. Application specific protocols are used here such as SMTP (simple mail transfer protocol) for sending emails from Outlook.

Presentation (layer 6)

This layer formats the data in a way that the receiving application can understand it. This layer is also able to encrypt and decrypt date if needed.

Session (layer 5)

This layer is responsible for establishing and terminating of connections between devices.

Transport (layer 4)

The transport layer of OSI Model is used for error handling and sequencing to unsure no data is lost. This layer also adds source and destination port numbers

Network (layer 3)

The network layer handles IP address routing. At this stage of the OSI model the source and destination IP address is added to the data.

Data Link (layer 2)

At this layer the physical address (MAC Address) is added to the data, this includes the source and destination MAC address.

Physical (layer 1)

The physical layer is the lowest layer of the OSI model. Its key responsibility is to carry the data across the physical hardware such as an Ethernet cable to the destination.

This video is designed to give a basic and general overview of the OSI model. Its aim is to simplify the concept to make it easier to understand.

#ccna #cisco #networking

[JamesTaylor-rater]

Thought i would post this here.
OSI Model explained:

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 standerize networks
in a way that allowed multi vendor systems. Prior to this, you would only be able to
have a one vendor network because the devices from one vendor couldnt communicate with
others. It is worth nothing that we dont 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 dont use the OSI model, why do we bother learning it?
Thats because its still referenced a lot when troubleshooting or describing network
operations.

Layers

Layer1: Physical layer
carries data across physical hardware.
User: ethernet cables.
Examples:
-are all the cables plugged in?
-Is the network card functioning?
-Could it be a faulty cable?

Layer 2: Data Link layer
At this layer, the physical addresses are added to the data. This is source and
destination mac addresses.
Switches operate at this layer
Example:
-Maybe the switch has gone bad?

Layer 3: Network layer
The network layer handles ip addressing and routing. At this layer, the source
and destination IP addresses are added.
Routers operate at this layer
Example:
-Is the router functioning?
-Do i have the right IP address?

Layer 4: Transport layer
This layer adds transport protocols such as TCP/UDP, and adds source/destination
port numbers.
Example:
-Could the internet card be functional?

Layer 5: Session layer
this layer is responsible for establishing and terminating connections between devices.
Example:
-Are you connecting to the correct address?

Layer 6: Presentation layer
This layer formats the data in a way the reciving application can understand it. This
layer can also encrpyt and decrypt data if needed
Example:
-Are you reading the data in the same order that you wrote it?

Layer 7: Application layer
This layer is where the application and user communicates
Applications used here such as SMPT, if youre sending an email for example.
Example:
-Is the application erroring out?

Accronym:
All 7-Application
People 6-Presentation
Seem 5-Session
To 4-Transport
Need 3-Network
Data 2-Data
Processing 1-Physical

[Rico-wpdg]

Amazing explanation. I work in Cyber Security and I've seen this explained a lot of different ways. People always want to over complicate it when you should be trying to simplify it...I guess it makes them feel smart when they over complicate it. Great job!

[annablaster]

I went to like a 3 hour lecture that was mainly focused on this and i kinda understand but didn't much. And the whole day today i've been on websites reading, watching videos. And yes going in dept is good but as a beginner i was having a hard time because some of the terms and words they used I haven't learnt yet or know much about only like the base concept of the terms. And this man just explained the entire model and how it works in real time situation in 6 minutes. OMG like i can't even thank you enough. I am glad this video is still on here after 6 years. I am so happy and grateful and a weight is lifted off my shoulders. And also it's even worst my professor have a thick accent i have to focus super hard to get what he is saying.

[ryanmajor]

I'm just getting into cybersecurity and I've learned a lot in my first 2 weeks but I was having trouble putting all this information together to paint a picture in my head and your explanation of the OSI Model was almost like an epiphany. I now understand how to apply what I've learned so far in Security+. Thank you very much!

[aliasad]

@2:55 Wow thanks a lot man! what an awesome way for students to pass their exams explaining OSI model layers
7) All (application layer)
6) People (Presentation Layer)
5) Seem (Session Layer)
4) To (Transport Layer)
3) Need (Network Layer)
2) Data (Data Link Layer)
1) Processing (physical layer)

[filipposilva]

The more I learn about networking, the more I realise how complicated and vast a subject it is. Dunning and kruger were right.
Thank you for these videos.

[proptbro]

This is by far the most clear, concise and clean explanation on youtube. Please make one for TCP/IP model too. Subscribed :)

[Mattador]

Studying for my Sec+ cert and have been stuck on understanding the OSI model for a while. Your real world example helped tremendously on my understanding of it. Much appreciated!

[sunilrayudu]

Never seen a short video for OSI Layers with most of the info covered. Thank you so much. Just needed a quick video to prepare for an interview. Your video has been a great help. Thank you

[princegandomessi]

I’m taking my CEH exam today and was reviewing my network part before I go. This video explained the OSI model perfectly and make it very easy for me, especially the example showing the flow of the layers when sending an email from the senders perspective and from the receiver’s perspective. Thank you and keep it up💪🏾💪🏾🔥🔥

[janitha]

Initially I thought this would be a boring explanation but now I change my mind..super clear

[ivesvanhouche]

Just started cisco networking course-this video is far more clear than the complicated explanation in cisco academy....

[lightingman]

Why are your videos so much easier to understand/watch than everyone else's? Seriously, so logically and simply explained!

[tax]

simply amazing I am a Masters Computer Science student and with this pandemic, the teaching level has really fallen below acceptable standards the material I am given doesn't even go into enough depth and their recorded videos are the most boring thing to watch this video literally covered everything I needed to know for the last week of my networking and architecture class thank you so much for this video and god bless the Interent.

[hawresalam]

I cant remember how many YouTube i watched to absorb this kind of fundamental networking ....but this channel is the King of explanations, that is it i am home!

[chadrochioli]

I've been watching your videos for a couple days now and I can't stop. I've always seemed to have troubles retaining the networking side of things, but you've seemed to get through. Great instructions, great video, great work. Thank you.

[texbiano]

You know alot of times one wonders if these conceptual models have real-life applications. Now, this is a true example of how to make a seemingly complex topic look easy. Fantastic job boss!!!

[taylornoumi]

I honestly have such a difficult time comprehending when just reading from books sometimes so I love your videos! They've been so helpful!

[gregbarkhamjr]

Currently taking my CIT 160 class and I was having a hard time understanding the OSI model but this video perfectly clears it up. Thank you so much.

[CBROWNS]

I've been struggling to get this for quite a while. This helped so much, and way more than other videos. Thank you.