How to understand what is TCP/IP?

Question

Computer networks

Good afternoon
For the umpteenth time I'm trying to understand how TCP / IP works and I can't get it.
As I understand it, there are four levels:

1. Applied
   
2. Transport
   
3. network
   
4. ducted
   

I've watched a lot of videos, but I can't figure out how this model works directly.
Let's start in order:

1) Applied The
data transfer protocol is selected here. Ok, let's say HTTP or HTTPs . And it has an API . There is such a JSON Server
plugin . There is a json database. But if I want to use OpenServer instead of JSON Server , can I do it with resin? Is it possible to connect to the SQL database via the REST API or in general how is it? It is not yet clear how the REST APIs themselves work in this system, but more on that in paragraph 2. 2) Transport



From the word transport, that is, data is transported, but it doesn’t happen at this level yet, does it? Are there 2 more levels?
And here we again choose the data transfer protocol as in the first paragraph. Are we transmitting via http already or what?

Next comes the network, and as I understand it, it transmits data over the wires, so what does the transport one do then ??? With a channel similar question ...

How much I'm looking for, I'm trying to understand, but the questions still remain. I would like to just figure it out once and for all and so that no stupid questions arise.

If you help me understand this, describe it in a human, simple, understandable language, then I think that you will help many dozens of novice developers. Every web developer should know this.

I sincerely thank those who will not remain indifferent to this issue.)

Answer 1

A series of articles "Networks for the smallest" on Habré.

Answer 2

Read Tanenbaum's textbook "Computer Networks".

Answer 3

Here you select the communication protocol. Ok, let's say HTTP or HTTPs. And it has an API
. There is such a JSON Server plugin. There is a json database. But if I want to use OpenServer instead of JSON Server, can I do it with resin? Is it possible to connect to the SQL database via the REST API or in general how is it?

Nichrome yourself suffered you, my eyes already climbed on my forehead.
The network route, the physical one directly transmits the bits. Transport controls the flow, controls transmission, resends lost packets, for example.
What source did you study? Vidyashki immediately in the trash, read books. I can tell you what. It's hard to explain in a nutshell.

Answer 4

video = non-educational material
read something from a selection of books

Answer 5

Your first mistake is watching videos instead of reading books. Hence the confusion in terms.
IP is a routing protocol, i.e. package delivery. Delivery is unreliable - packages can get lost, duplicated, and delivered out of order.
Those who are not afraid of this use UDP. And those who do not want to deal with these problems - use TCP, which tracks the problems of the IP protocol.
The layered protocol model is easiest to think of as a hierarchy of subroutines that call each other.
The channel protocol, roughly speaking, determines the way data is encoded in the cable: the modem whistles at an audio frequency (from 300 to 3000 hertz), and Etnernet at 10 or 100 Mbps uses a frequency approximately equal to the data transfer rate - from 5 to 10 MHz or from 50 to 100 MHz respectively.

Answer 6

Theory without practice is dead. For practice, take WireShark, isolated mesh and play.
If you're programming, try writing a simple application using TCP to understand it, and then play around with the data using WireShark to see how it all works. It is possible for the general development to begin with UDP - it is more clear.
After reading the books, I had some idea, but when I had to write DHCP / BOOTP and TFTP servers at work, everything became quite clear. Then I also programmed on SLIP/TCP.
It turned out to be very useful.

Answer 7

I understood a lot after the course https://lagunita.stanford.edu/courses/Engineering/...