Thread by @TechladyTaeTae

Here are some OSI notes that I took, courtesy of Mike Meyers.

Check him out here:

totalsem.com/network-plus-c…

Q: What is a model?

A: a simplified process that represents how networks function.

So not this diva. The other type of model.

✅There is the OSI model
✅There is the TCP model

(Guru99.com)

It takes a lot of software + hardware that allows a network to function. All devices have to work together, and to help connectivity work, they came up with the OSI model.

If you work in an office type environment, then you know what I’m getting at.

Now that we see what the OSI model is, let’s discuss how data moves through a network. Starting with an Ethernet Frame.

This is it. A whole Ethernet frame.

We start with the Frame Check Sequence (FCS).

It’s going to check the entire frame to ensure the entire frame is in good shape.

Once the ETHERNET FRAME enters the Network address card, the FCS, SOURCE MAC ADDRESS, AND DESTINATION MAC ADDRESS are stripped from the frame.

Now the ETHERNET FRAME is an IP Packet.

And this baby right here? That’s an IP PACKET.

The network card will store the SOURCE MAC + DEST MAC addresses, because it may want to send another frame out at a later time.

The FCS operates at THE NETWORK INTERFACE LAYER (LAYER 1) OF THE TCP/IP MODEL, and at the PHYSICAL LAYER (LAYER 1) of the OSI MODEL

The network card storing the MAC addresses operates at the NETWORK INTERFACE LAYER (LAYER 1) OF THE TCP/IP MODEL, AND THE DATA LINK LAYER (LAYER 2) of the OSI MODEL

Now the packet is at the NETWORK LAYER

The NETWORK LAYER Deals with IP addresses

At this layer, the SOURCE IP + the DESTINATION (DEST) IP is checked to ensure that it is for the receiving client.

One it is established that the packet is for the client, the DESTINATION IP will be stored.

Now we’re left with a TCP segment.

Now we go up a layer to the TRANSPORT LAYER.

The TRANSPORT LAYER assembles and disassembles data.

If the data is big, it is chopped up into bite sized chunks at this layer.

If the data is coming in, it is assembled at this layer

At the transport layer, once the sequencing number is taken off (because it’s been reassembled), what is left are the port numbers, and the next layers will need them.

Now we’re at the Session Layer (OSI)/Application Layer (TCP/IP)

Session layer will connect to something, especially for remote clients.

A connection will be made. Maybe not a love connection, but a connection will happen.

The Presentation Layer puts data into a form that the user can read (like a .doc, .xls, .jpg format)

In the APPLICATION LAYER, we are talking about the built in technology that allows applications to interact with each other.

It looks at the port numbers
The return port number will store it in case it has to use it again.

Maybe it won’t store it here though…

And that’s it. That’s the post.

Happy studying!

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