I’m not a computer science student. But I want to learn it and grasp these two models in very simple language and terminology.
In: 7
A computer is like a whole city of people and everyone has a job to do and relies on the others doing their job. So to get the internet on your screen, computers need to talk a lot to make sure everyone knows what needs to be done and when they should do it etc. But all that talking is very confusing if everyone is in the same room, so some smart people told everyone to go to a separate room, so those who need to talk to each other can do so without being distracted and confused by all the other things going on in the city.
So for OSI they decided to make 7 rooms but for TCP/IP they said 5 rooms are enough. (If you want to make a boomer OSI joke, say something like “I seem to have layer 8 issues, nothing gets done on my computer”, because the user in front of the screen is sometimes called layer 8)
As I said before it’s about getting the internet to your computer.
So you start with the lowest layer (1), being the actual cable. So all the cable people go to room 1.
Like the car mail gets delivered in.
That cable goes to your router. That connection is layer 2. So all the people who deliver mail only in your neighborhood but not further go to room 2. It could be enough to tell them to bring the mail to house number 7 and they wouldn’t need more to know where to deliver it. (MAC addresses)
Layer 3 is for delivering outside of the neighborhood. Now you need to write down the exact address, with zip code etc, because otherwise the mail service wouldn’t really know where to go with the letter. In room 3 people just talk about where things are and how to get there. They are really good at that. (IP)
In room 4 people start talking about how to deliver the mail. Is it important that you get a letter back once your letters arrived, so you can be sure they all arrived in good condition, or is it enough to just send it and hope for the best? (TCP/UDP)
The 5th room talks about the letter itself. What should we put in there? What language should the letter be written in so the recipient understands it as well? Should we use abbreviations, so we can fit more of what we want to say and show? Should we introduce ourselves first? Maybe we should ask if they can send us their favorite poem back, because we got told by the boss (you) that we need to get poems from the person we send our letters to.
In OSI they split up the 5th room/layer in 3 separate rooms.
Here you can see the names of those rooms (might be helpful to read more about specific layers that caught your interest): https://1.bp.blogspot.com/-brz99Xq77EY/WIi6f-eklDI/AAAAAAAAD_g/V1_zENy22dkofjfoYAyaKvj6Z5gYJxDOACLcB/s1600/tcp-ip-vs-osi.png
So next time you have no internet connection (no letters are arriving), you can take one of the models and use them for troubleshooting. You could start with layer 1 for example and check if the cable is actually plugged in. Then you could try to ping your router to see if that connection works, or open the settings page of the router in your browser. And so on.. (it’s probably the DNS server, if it’s not DHCP.. it’s always one of those two in room 5/7, so you might just start there if you don’t regularly unplug your computer)
If anyone finds mistakes, outdated knowledge or anything alike, let me know please, it’s been some time since I learned about those models. Learned that TCP/IP now has 5 layers while looking for pictures for example.
Latest Answers