An interesting explanation of OSI's understanding at various levels (traders from Spain to Rome)

An interesting explanation of the various layers of OSI (traders from Spain to Rome) Case study: traders from Spain to Rome this part is a key part of OSI's understanding of layer-7 models, the creation of this situation allows students to understand why OSI is currently set to seven layers and give explanations accordingly. The main method is to use analogy to enable students to understand why they want to divide the Internet into these seven levels by using the situation settings of a Spanish trader going to Rome. The main purpose is to let the students know the significance of this reference model, but do not introduce the detailed functions of each layer too much. 1. To succeed in trade, we must first have at least one path from Spain to Rome. This layer is the physical layer. 2. Can I trade it if I have a path? It is also necessary to ensure that the merchant's goods will not be damaged on the road, and there must be a layer of protective packaging. The second layer is the data link layer. 3. The so-called routes allow Rome. There is not only one path to reach Rome, so it is in the interests of businessmen to choose the shortest path or the lowest cost of the road. The third layer, network layer. The above three layers are the lower three layers in the network, called the media layer. Let's take a look at the other four layers. 4. Check your goods before going out of the trade. Are there any errors? Check them in advance. If yes, re-Fetch the goods, leading to the fourth layer, transport layer. 5. Can I get on the road? Not yet. We need to contact Rome. What if the goods on our side cannot be sold there? First of all, we need to exchange and negotiate with each other to check the market conditions in Rome. If we can cooperate with another businessman there, it will be better. This requires diplomatic relations. It is called the Session Layer. 6. It seems that everything is ready, but when the merchant arrives in Rome, he suddenly finds that no one in his business team can understand the words of the Romans, and no one in Rome can understand Spanish. At this time, another translation is required, either to convert both languages into an international common language, such as English, or at least to allow communication between the two parties. This is the presentation layer. 7. When it comes to Rome, we eventually need to sell the goods on the exchange. This exchange is a trading platform, which is equivalent to each software platform, leading to the last layer and the application layer. At this time, the students will have a general understanding of OSI, which can basically grasp the reasons for layering and the characteristics of each layer. Here, we will discuss several groups to better understand OSI. 1) use the knowledge of network devices learned in the previous lesson to group and discuss which devices belong to the next layer. 2) Instruct Students to discuss how to join certain agreements through problems that may occur during the trade trip to Rome, such as weather disasters, expiration, and theft, so that the entire trade process can be effectively protected, so that trade can be completed smoothly. Through understanding the process of situation 2 and the discussion of the protocol, students can understand the importance of the Protocol in the entire network communication process and how it plays an important role. The most important layer about the protocol in the network is the transport layer. This paper introduces the important role of TCP protocol, and explains the difference between the role of TCP protocol in the transport layer and other protocols in the presentation layer. And let students think about which network layer the IP protocol plays a role in.