How to remember the OSI seven layer protocol model, the brain hole opened with wood?

Everyone who has studied computer networks must know the OSI seven layer protocol model. The OSI layer Seven protocol model (or OSI seven layer model) is a well-defined protocol specification and is considered a standard reference model for interconnection of modern open communication systems. The OSI model has 7 layers of structure, each of which can have several sub-tiers. The 7 layers of the OSI are from top to bottom, respectively:

• 7. Application Layer--application (layer 7)

       An application that communicates with other computers, which is the communication service of the corresponding application. For example, a word processor without a communication function would not be able to execute the code of communication, and the programmer working on the word processing did not care about the 7th layer of the OSI. However, if you add an option to transfer files, the programmer of the word processor will need to implement the 7th layer of the OSI.

• 6. Presentation Layer--Presentation (layer 6)

The primary function of this layer is to define the data format and encryption. For example, FTP allows you to choose to transfer in either binary or ASCII format. If binary is selected, the sender and receiver do not change the contents of the file. If you select ASCII format, the sender converts the text from the sender's character set to the standard ASCII and sends the data. Converts standard ASCII to the receiver computer's character set on the receiver side.

• 5. Conversation Layer-session(layer 5)

it defines how to start, control, and end a session, including control and management of multiple two-way messages, so that the app can be notified when only part of a continuous message is completed, so that the data that the presentation layer sees is continuous, and in some cases, data represents the presentation layer if all the data is received by the presentation layer.

• 4. Transport Layer-- Transport (layer 4)

The functionality of this layer includes whether to choose the error recovery protocol or the error-free recovery protocol, and to reuse the input of data streams from different applications on the same host, as well as the reordering of packets that are not received in the wrong order.

• 3. Networking Layer-Network(Layer 3)

This layer defines the end-to-end package transport, which defines the logical addresses that identify all nodes, and defines how and how the routes are implemented. To accommodate transmission media with a maximum transmission unit length of less than the packet length, the network layer also defines a segmentation method that decomposes a packet into smaller packets.

• 2. Data Link layer-link2

It defines how data is transferred on a single link. These protocols are related to the various media being discussed.

• 1. Physical Layer--physical (layer 1)

The physical layer specification is a characteristic standard for transport media, which is often referenced by other organizations ' established standards. Connection head, frame, frame use, current, encoding and light modulation are all the contents of various physical layer specifications. The physical layer often uses multiple specifications to complete the definition of all the details.

A more troubling question is how do you keep the 7 layers in order, without missing them? the netizen of the Big brain move opens a lot of memory formula (do not know which you like?) ）：

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2.PLeaseDoNotTellS tupid PeopleAnything

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Finally, we show that the top level of the seven layer protocol, namely 7, 6, 5, 4 layer defines the function of the application, the following 3 layer, 3, 2, 1 layer mainly for the end-to-end data flow through the network. Examples of specific protocols included in each layer are given in the following table:

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How to remember the OSI seven layer protocol model, the brain hole opened with wood?