Today, let’s take a look at OSI (Open System Interconnect). It is a network interconnection model released by the ISO organization in 1985. The standard defines a seven-layer framework for network interconnection. The content is briefly described as follows:
In our office or at home, we purchase some network equipment. There are usually three types searched on websites such as JD. They are hubs, switches, and routers. Here are the differences between them at the network level.
hub works at the first layer (physical layer) of OSI, and only forwards electrical signals to the devices connected to it, and does not do other processing.
switch is a layer 2 (link layer) device, which is addressed by sending broadcasts in the same network segment, using the obtained MAC address of the target host to communicate with hosts on the same network segment. In addition, there is also a switch with added routing function on the market, which we call a layer 3 switch.
router is a layer 3 (transport layer device) device that learns from each other to generate and maintain a routing table, and is responsible for addressing and forwarding in a cross-network segment environment.
In subsequent articles, we will introduce some network protocols, services and commands.
Here, please think about a question first. What are the possible causes of what we usually call "the computer cannot access the Internet"? How do you generally locate the problem?
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