Introduction to the OSI Model

This topic is to discuss the following lesson:

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thank you for helpful lesson.
i have a question about osi layers,are layers 5,6,7 in our browser(firefox,chrom…)? what about the rest of layers?for example is layer 2 only started to working when frame gets to switch or all these happen in pc in advance?
it is a big question for me and mixed me up.

Hi Reza,

Your computer has to deal with all of these layers. When an application wants to send some data it will start at the top of the OSI model (layer 7) and will work its way down the stack, you can’t skip any layers. Your computer has to create an Ethernet frame before the switch can receive anything :slight_smile:


thank you Rene

Its really easy and simple to understand and refer

Thanks again!

thanks for ur info

Rene thanks so much. I always read your lessons to refresh my memory. I am CCNP now thanks to the excellent work you are doing.

I like your acronym better than the one about sausage pizzas!

thank you

thank you,you really make me understand osi module




Best summary of OSI layer i have come across.


Nicely done, thanks!

Excellent explanation of the OSI model and how it works. Thanks a lot

This lesson was well written and straight to the point. I’m in the process of refreshing to take my CCNP. Good job :slight_smile:

Thanks Darryl!

I have a doubt
If my network is a local area network without internet(for example computer and printer) then there is no need for upper four layers right?

Hi Ranjitha,

We always use all 7 layers of the OSI model, it doesn’t matter if it’s LAN or WAN. There are no exceptions.


The reason this article is confusing or doesn’t make sense is it describes accessing a local web server by typing in a URL. Then goes on to say the web servers MAC address is encapsulated at layer 2. How would the computer know the MAC address of the web server? The only way this makes any sense to me is if the user typed in the web server’s IP address and not the URL and the web server was not only local but on the exact same subnet.

Hi James,

When I’m talking about a local webserver, I mean one on the same subnet…not localhost or on the Internet. Typing in an IP address or URL doesn’t make much of a difference, the only difference would be that when you use a URL that we have to do a DNS lookup to figure out the IP address.

Once you have the IP address, we can do an ARP to figure out the MAC address of the webserver. If it would be on another subnet, we’d do an ARP for the IP address of our default gateway.