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. Durga,
    OSI and TCP/IP are both models, and TCP/IP is a currently implemented model. An interesting fact is that there was, at one time, an actual OSI protocol that followed the 7 layer model of OSI. The OSI protocol (obviously) lost out to TCP/IP.

  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 guys,

    I’ve read in the ICND1 100-105 book that the TCP/IP model has an updated version, with Internet layer becoming Network layer and Link layer split in Data Link and Physical layer (just like in the OSI model)

    Is this new version became a de facto or we can still consider the original TCP/IP model (RFC 1122) ?
    I’m just wondering if in the exam they refer to the original or updated version?

    Thanks.

  4. 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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  5. @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.

    Regards,
    Soren.

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