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This article will explain in detail what the functions of the application layer are, and the content of the article is of high quality, so the editor will share it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

The OSI application layer is the seventh layer of the open systems interconnection (OSI) seven-layer network protocol model and TCP/IP protocol, and it is also the only layer that interacts directly with end users. The application layer protocol contains protocols for network inter-process communication, and provides a stable communication interface and end-user services.

The top layer of the OSI seven-layer model is the seventh layer: application layer, Application Layer

OSI application layer functions: the application layer provides a variety of application layer protocols, which are embedded in a variety of applications we use to provide an interface between users and the network.

The role of OSI Application layer

When we first learn about the network, the concept of the network will not be very intuitive. When we use the network, what we see with the naked eye is not the network, but a bunch of computers, network devices, and then connected by a bunch of wires, this device. The network is only after these devices are connected to each other and then planned and configured by the network engineer. The network does not exist in physical form, it cannot be seen or touched.

When we use all kinds of network applications, we have built-in application layer protocols. For example, IE browsers use the HTTP protocol at the application layer; the application layer protocols used by QQ are SMTP and POP3 protocols used by OICQ;Outlook to send and receive email.

It should be noted here that the software we use are applications, which are only developed by software developers, these applications are just a shell, and the protocols embedded in these software are the content of the application layer. Programs that use the network need integration protocols before they can be used properly.

Here are a few common examples of how the OSI application layer deals with us:

If we want to look at the web page, open the IE browser, enter a URL, and enter the corresponding website, then this IE browser is my application tool for browsing the web, and it also works in the application layer. IE browser is developed based on HTTP protocol, and HTTP is an application layer protocol.

If we want to upload and download a file using FTP, we will first open the FTP client, and then connect to the FTP server, which is the tool of the application layer. FTP client is developed based on FTP protocol, and FTP protocol is also an application layer protocol.

I will send an E-mail, I will install a Foxmail, Outlook and other mail client software on the computer, and then edit the email and send it to the appropriate person. Outlook and Foxmail are developed based on SMTP and POP3 protocols, and SMTP and POP3 are also application layer protocols.

There are many protocols in the application layer, and now most of the network tools are developed based on these programs.

The PDU of the application layer is: APDU (application layer protocol data unit)

What are the functions of the application layer to share here, I hope that the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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