I started to study the OSI network model, I ran into difficulties understanding.

5 Answers 5

Is it crucial for you to learn the OSI reference model?

It's just that for practice they teach the TCP/IP model, where there are four levels, not seven, it’s easier there.

If there is a problem with understanding, perhaps you should change the book.
The simplest interface concept is a power outlet and a plug(or plug).Each outlet has its own type of plug, for example, different countries have different standards.
And here the transmission line transmits some information(let it be 220V voltage), and to connect to this information you need an interface from one and the other side(connectors or a plug-socket).".
If all this is transferred to the software level, then the concept of the interface can be added"determine the type of outlet","apply power","signal the receiver and transmitter","reserve the load, bandwidth", etc.
Thus, a set of operations in the form of an"interface" determines those operations that the upper level can do with the lower one, without worrying about the realization of the lower level..
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you do not worry, learn and practice, then you will overtake the practical, especially as in TCP/IP levels are not 7, but 4

write yourself a question right away: why you cannot make a VPN through a proxy
and the second: as providers transmit for kilometers, when the twisted pair length of the 5th category is a maximum of 100-180 meters
the answer to the first will help on the programming life, on the second - to declare that OSI understood
A protocol is a set of rules by which actions and transmission of information occur within a single level.
The interface is the same protocol, but for communication between the levels.As this is exactly what happens, it’s impossible to explain with fingers, but if the difficulties do not frighten you, start with RFC-1122.
I don’t know how it can help, but I advise you to use wireshark to start exploring protocols, where you can clearly see what is happening + there and the wiki is not bad(not rfc of course ..).
I would explain it like this: 1 - always physics(hardware means of receiving/transmitting a signal), 2 - logic(from a level 1, infe is given a certain structure, depending on the type of network(ethernet, PPP ..).In the second level, protocols are encapsulated above For example:
browser request to the site in OSI=
7.HTTP structure
6.utf-8 or other encoding set to a higher level
5.TLS encryption
4.TCP socket(the port is set here)
3.IP
2.Ethernet/PPPoE and TP.
1.cable/wifi rx/tx