OSI reference model layers | OSI model layers functions

In that article OSI reference model layers The OSI model (Open System Interconnection Model) is a conceptual framework used to describe the functions of a networking system.

OSI reference model layers:

  1. OSI’s layer is a collection of conceptually similar functions that serve the upper layer and receive services from the lower layer.
  2. OSI’s main concept is that the communication process between two endpoints in a telecommunication network can be divided into seven different levels of related work.
  3. Each communicating user or program is on a computer that can provide those seven levels of functionality.
  4. So in a given message between users, the data source goes down through the layers of the computer and then goes up through the layers of the received computer.
  5. The seven levels of function are provided by a combination of application operating system, network card device drivers and hardware capable of sending signals over a network cable or Wi-Fi or other wireless protocol.
  6. In the OSI model, the control starts from one station to another, starts from the layer application layer (level 7) at one station and slides down, moves to the next station on the channel, and the hierarchy is backed up. The OSI model serves the function of inter-networking and divides it into sections known as vertical stacks with 7 layers below-
OSI Reference Model
OSI Reference Model

1) Physical layer:

  1. The bottom layer of the OSI reference model is the physical layer.
  2. It is responsible for the actual physical contact between the devices.
  3. The physical layer contains information in the form of bits.
  4. It is responsible for the actual physical contact between the devices.
  5. When receiving data, this layer receives the signal. It then converts these layers to 0 and 1 and sends them to the data link layer.
  6. Examples of physical layers include Ethernet cables and token ring networks.
  7. In addition, hubs and other repeaters are standard network devices that operate on the physical layer, such as cable connectors.
  8. On the physical layer, data is transmitted using signals supported by physical means: electric voltage, radio frequency or pulses of infrared or ordinal light.

Important points of physical layer:

  1. Physical Activates maintains and deactivates physical connections.
  2. Transmission is responsible for transmitting and receiving non-structured RAW data from the network.
  3. Transmission the voltage and data rates required for transmission are defined in the physical layer.
  4. Digital converts digital / analog bits into digital signals or optical signals.
  5. Layer data encoding is also done in this layer.

2) Data link layer:

  1. When retrieving data from the physical layer, the data link layer checks the physical transmission error and packets the bits into a “frame”.
  2. The data link layer also manages physical addressing schemes such as MAC addresses for Ethernet networks, controlling access to any variety of network devices for physical media.
  3. Since the data link layer in the OSI model is the most complex layer, it is often divided into “Media Control Access Control” sublayer and “Logical Link Control” sublayers.

Important points of Data link layer:

  1. The link data link layer synchronizes the information transmitted to the physical layer.
  2. The main function of this layer is to ensure that the transfer of data from one layer to another node at the physical level is error free.
  3. Received transmissions and data frames are managed by this layer, respectively.

OSI reference model layers:

3) Network layer:

  1. The network layer edits the concept of the top path of the data link layer.
  2. When the network arrives at the network layer, it checks the source and destination address in each frame to ensure that the data has reached the final stage.
  3. If the data reaches the final destination, it will format the data in the packet reaching the level 3 transport layer. Otherwise, the network layer updates the destination address and puts the frame back in the lower layer.
  4. To support routing, the network layer maintains a logical address, such as an IP address, for devices on the network.
  5. The network layer also manages the mapping between the logical address and the physical address. In IP networking, this mapping is accomplished via the Address Resolution Protocol (ARP).

Important points of Network layer:

  1. One navigates through different channels from one node to another.
  2. It acts as a network controller. It manages subnet traffic.
  3. Which data decides which path to take.
  4. Going splits outgoing messages into packets and aggregates incoming packets for the message.

4) Transportation layer:

  1. The transport layer sends data over a network connection.
  2. The most common example of the Transport Layer 4 network protocol is TCP.
  3. Different recovery protocols support a range of alternative capabilities, including support for error recovery, flow control, and re-transmission.

Important points of transport layer:

  1. Responsible for the interaction of data between end systems.
  2. Responsible for end-to-end error review and flow control.
  3. Data is responsible for the entire data transfer. SP has protocols like SPX, TCP, UDP function.

5) Session layer:

  1. When two devices, a computer or a server, need to communicate with each other, a session is required and this session is done layer by layer.
  2. The functions of this layer include setup, coordination (e.g. how long the system has to wait), and termination of the application at each end of the session.

Important points of Session layer:

  1. Session Establishment Responsible for establishing, managing and terminating connections between application forms.
  2. Layer seventeen sets the coordination, exchange, and interaction between applications at each end.
  3. Session works in conjunction with sessions and connections.
  4. Protocols like NFS, NetBioze names, RPC, SQL work on this layer of FS.

OSI reference model layers:

6) Presentation layer:

  1. The data from the application layer is retrieved here and handled according to the format required for transmission through the network.
  2. The functions of the presentation layer such as follow:
  3. Translation: e.g. ASCII to EBCDIC Encryption / Decryption: Data encryption translates data into another form or code.
  4. Encrypted data is known as cipher text and decrypted data is known as plain text.
  5. A key valuator is used to encrypt and decrypt data. Compression: Reduces the number of bits transmitted over a network.

Important points of Presentation layer:

  1. The presentation layer takes care that the data is sent in such a way that the recipient can understand the information (data) and be able to use the data.
  2. While receiving the receiving data, the presentation layer creates and converts the data for the application layer.
  3. Communication The syntax of a language can be different in two communication systems.
  4. In this case, the presentation layer acts as a translator. Data does data compression, data encryption, data conversion, etc.

7) Application layer:

  1. At the top of the OSI reference model is the application layer, which is implemented by the network application.
  2. These applications generate data, which is transferred from the network.
  3. This layer serves as a window for application services for network access and displays information received by users.
  4. Web browsers (Google Chrome, Firefox, Safari, etc.) or other apps – Skype, Outlook, Office – are all examples of level 7 applications.

Important points of Presentation layer:

  1. Presentation layer supports caching, apps, and end-user processing.
  2. This layer is responsible for application services for file transfer, e-mail and other network software services.
  3. Layer protocols like Telnet, FTP, HTTP work on this layer.

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Santosh Nalawade

Work as Assistant Professor and Web Developer.

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