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Clarification: I already read the answers in OSI Models and Networking Protocols Relantionships question, and doest not resolve my doubts.

Good day, I have been studying and reading an introduction to networks and I want to know if I have understood it correctly.

A data network is a set of computers connected (in some way) to share information with each other. To carry out communication between these devices, a series of functions must be performed such as bug fixes, define the best communication path, data transfer velocity, route data and much other functions.

Due to the large number of functions, the notion of separating them by "layers" was born. In each layer, we separate a set of similar functions from each other.( 1* Is this the definition and origin of layers?)

And here also the protocols are born, which will tell us HOW these functions are carried out, with the aim that the communication between different devices is compatible. Therefore, there should be a protocol for each layer. For example, in a layer that takes care of errors, there will be a protocol that will tell us what to do when we find a certain X error.

Delving a little deeper into the layering model, we have the following characteristics:

It is sequential, that is, it goes through each layer before reaching the last one. Therefore there is a communication between adjacent layers called an interface.(2* is this correct?)

The number of layers and their functionalities will depend on the type of model (for example, OSI or TCP / IP) and the type of device that the model uses. For example, a computer will use all 7 levels of the OSI model, but a router only 3 (physical, data link and the network layer).

Furthermore, since each layer is a set of functionalities, then the "output" of these functions is "encapsulated" to start of the message in what we call "header". Also sometimes you can add the "output" of these functions at the end of the final message, called "tail" or "trailer".(3* is correct?)

Well, this is what I have understood. The paragraphs in which I have doubts as to whether what I wrote is correct are those marked with a number and the asterisk because i am not totally sure of that. Specially in 1* I have doubts. Each layer represents a division of a set of functions? Or does each layer represent something else? (I read in another question on this forum that it represented a protocols division, so that makes me very confused).

Also, if you find an error in any paragraph of what I understood, please help me understand it.

Thanks in advance.

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  • "Due to the large number of functions, the notion of separating them by "layers" was born." No, the layer models were developed to explain how things ideally work or should work. The models a just models, and many things in the real world do not follow the models or fit into one of the model layers. "For example, a computer will use all 7 levels of the OSI model" No, nothing implements the OSI model.
    – Ron Maupin
    Apr 18 at 20:30
  • Just take away the ideas of abstraction and encapsulation, but trying to make everything fit into one of the models will drive you to insanity.
    – Ron Maupin
    Apr 18 at 20:33
  • Look at the questions under the OSI and TCP/IP Models section in this meta question.
    – Ron Maupin
    Apr 18 at 20:37
  • oh man! I have read all those questions over and over and I cannot answer my questions. Many of the answers contradict each other Apr 18 at 21:16
  • Only 2 is correct.
    – Ron Trunk
    Apr 19 at 0:53

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