TCP/IP Stack Tutorial

Besides the OSI model there was another organization that created a similar reference model which never became quite as popular.

When I’m talking about “not popular” I mean the TCP/IP stack model isn’t used often as a reference model…when we talk about layers, people always refer to the OSI model. On networks nowadays we use TCP/IP all the time…

However if you are studying for Cisco CCNA you’ll need to know what it looks like. It’s called the TCP/IP stack and it’s similar except some of the layers are combined and have different names. Here’s what it looks like:

TCP/IP Stack

As you can see the upper three layers are now combined to the “Application layer”. The network layer is called the “Internet” layer and the bottom 2 layers are combined into the “Network Access” layer.

Here’s a comparison between the two models:

TCP/IP Stack vs OSI Model

Basically it’s the same idea, same model except with some layers combined and different names.  The physical and data link layer are combined into the network access layer. The network layer is now the internet layer and the session, presentation and application layer are combined into a single application layer.


Forum Replies

  1. Hey Rene. Please help me here. I’m getting confused with OSI and TCP/IP. From Wendell Odom Book it says TCP/IP in the model being used in networking while OSi is just used for referencing but on the above article you are saying TCP/IP was never popular and OSi is the one being used.

  2. Hi Rene\Andrew,

    So are you saying both OSI and TCP\IP models were introduced as a reference models(theoretical model) by 2 different organizations and later TCP\IP became popular to implement in real world . Couldn’t they try to implement OSI stack ? I see only TCP\IP stack in all the computers in today’s world.

  3. Hello Sorin

    Yes, this is Cisco’s attempt to promote this new TCP/IP model in their curriculum, and to be honest, it’s not a bad idea. When we talk about networking, we usually use the OSI model layer names and numbers. We talk about a L2 or L3 switch, or L2 functionality as switching and L3 functionality as routing, and L4 operation as TCP sessions and UDP datagrams. The problem is that all of these technologies are not actually modeled around the OSI model but around the TCP/IP model. So according to the TCP/IP model, switching is L1, routing is L2 and TCP

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  4. @lagapides,

    Thank you for your explanation, make sense of what you say.
    I just hope I won’t get confused. There are three network models (ISO, TCP/IP, TCP/IP updated) that more or less look the same and they were supposed to define a common standard.

    Anyway thanks again.


  5. Thank you Lazaros Agapides for your explanation it is very clear :grinning:.

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