Application layer of the OSI model and its functions

len Alfred Ajibola - 27th October, 2021 @ 08:50 AM

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What is the first step towards disabling automatic image download on WhatsApp?

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Twitter was launched in _____.

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Application Layer:

The application layer or layer 7 of the open systems interconnection (OSI) model is the first point of contact when a user interacts with the internet or intranet. Simply put, it is the first point of network communication from the perspective of the end user. As an instance, you were able to read this article on LenAcad because the application layer on your phone or computer device had been put into use through your web browser.

Please read an introduction to the OSI model here.

To buttress the above paragraph, take a look at the Uniform Resource Locator (URL), which happens to be the link of this page on your browser. It should look something like this:


Notice the 'https' protocol from the above URL. It may be http in some other websites. The 'https' protocol is always present on the application layer whenever we access the web. In fact, it is the application layer protocol for the web.

HTTP stands for 'HyperText Transfer Protocol' while the 's' in https means that the protocol is secure.

HTTPS means HyperText Transfer Protocol Secure

Other protocols found at the application layer include:

  • Telnet

  • File Transfer Protocol (FTP)

  • Secure Shell (SSH)

  • Domain Name Service (DNS)
    Please read on DNS and how it works here.

  • Dynamic Host Configuration Protocol (DHCP)

  • Simple Network Management Protocol (SNMP)

  • Trivial File Transfer Protocol (TFTP) and so on.

You can read on the transport layer of the OSI model here.


The application layer is also responsible for various application services like email, remote file access, facebook app and other apps (on your phone or computer) requiring the internet to function.

Understand that application services require an internet or intranet to function properly. Recall that the internet is a global and public network while the intranet is considered a private network within an organization.

Please read more on the internet and world wide web here.


Functions of the application layer

  1. The application layer provides an interface for various services like email and network file control.

  2. Users are able to view their internet activities via the application layer.

  3. Various protocols present at this layer aid the users to interface with one another in a communication network.

  4. This layer is responsible for the synchronization of communicating partners, while also presenting their identity to one another.

  5. Application layer brings about the utilization and usage of various softwares by different users.

  6. In a attempt to access local or remote files, users can login through the application layer.

  7. Security of the users and their devices are ensured since each application interacts specifically with an operating system.

  8. Various application protocols like https, DHCP and DNS are required for internet access.

  9. Application users are able to access, read, write and retrieve files from a remote computer within or outside a network through the application layer.

  10. Generally, the application layer provides access for global information on a variety of services.

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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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Physical parts of a computer are those parts that you can see and touch. It may also be referred to as the 'equipment of the computer'.

When the computer case is opened (with a screwdriver), one would see the different hardware components inside of it. It's important to state that some other hardware components are present outside the computer case; and these are termed peripherals.

Below are hardware components seen inside the computer case:

  • Motherboard

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  • Graphics Processing Unit (GPU)

  • Power supply Unit (PSU)

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  • USB port, PS2 port, Ethernet port and other ports

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Hardware components seen outside the computer case are called peripherals. The peripherals are grouped into the following:

  1. Input devices: They provide information to the computer.

  2. Output devices: Brings out information from the computer.

  3. Storage devices: They store information or data.

Below are examples of some peripherals:

  • Keyboard (input)

  • Monitor (output)

  • Mouse (input)

  • Webcam (input)

  • Touch Pad (input)

  • Universal Serial Bus (USB) flash drive or memory card (storage)

  • Hard disc drive (storage)

  • Stylus (input)

  • Joystick(input)

  • Printer (output)

  • Speaker (output)

  • Headphones (output)