Functions of OSI Layers

Open System Interconnection (OSI) Model developed by the International Standards Organization (ISO) which describe the flow of information from one computing device to another. OSI model is likewise called ISO OSI reference model.
Here, PC 1 is sending data to PC 2. In this process, the data will transfer from different layers, and it is well explained by OSI Model.

The Seven Layers

1. Physical Layer

This includes the cable and wireless connections among devices as well as the specifications of the jacks, plugs, voltages etc.

2. Data Link Layer

It provides the direct protocol connection between two nodes on a network and handles error connection from the physical layer.

3. Network Layer

This is the routing layer at which packets are forwarded from their source to their destination.

4. Transport Layer

This layer coordinates the transfer of data between systems and hosts by specifying such thing as how much data to send and at what rate.

5. Session Layer

For two devices to transact specific functions between each other a session is required. Session layer handles setting up sessions, coordinating the rule of communication, such as how long to wait for responses and how to terminate the session layer.

6. Presentation Layer

At this layer, data is prepared for presentation between layers, for example, data that is encrypted across a network would be decrypted at this layer for presentation to an application at the destination device.

7. Application Layer

This is the layer at which applications are displayed to the end user.

How does data flow?

Terminologies

Packet:

While imparting through networks it’s vital to send and get documents and data. The fundamental unit of correspondence between a source and an objective in a network is a packet.

Frame:

Like packets, outlines are little pieces of a message in a network. It assists with distinguishing information and deciding the manner in which it ought to be decoded and deciphered. The primary contrast between a packet and a frame is the relationship with the OSI layers.

Segment:

A segment is a wrecked piece of a packet with a TCP header in every one of them. Close by the source and objective ports, it contains the checksum field that guarantees the past information’s accuracy through the network. Segments increment the productivity of network execution and further develop security.

Binary Bits:

A binary digit, or bit, is the smallest unit of information in a computer. It is used for storing information and has a value of true/false, or on/off or 0/1.

Functions of The OSI Layers

1. Physical Layer

  • Converting bits to a signal during the transmission medium and again converting the signal into bits and pass it on to the receiver
  • Use different types of encoding methods to convert a signal to a bit
  • Determine the transmission rate of data
  • Synchronize the bits both for the sender and receiver
  • Establishing and termination of physical connection between two communication systems
  • Shares communication resources among multiple users. Including networks such as contention resolution and flow control

2. Data Link Layer

  • HOP to HOP delivery (point to point protocols)
  • Error control
  • Flow Control
  • Framing
  • Uses both LAN and WAN Services to arrange Bits from physical layers in logical sequences called Frames.

3. Network Layer

  • The network layer conventions figure out which course is reasonable from source to destination.
  • The source and collector’s IP addresses are put in the header by the network layer. Such an address separates every device interestingly and all around.
  • Maintain Quality of service when transmitting data sequence from one source of network to other(host) source of network as requested by transport layer.
  • This layer Performs Network routing function, fragmentation & reassembling
  • Reports Delivery errors
  • Network layer performs various layer-Management protocols like
    a) Routing protocol
    b) Multicast group management
    c) Network layer information and error

4. Transport Layer

  • This layer acknowledges the message from the session layer, breaks the message into more modest units. Every one of the segments created has a header related to it.
  • To convey the message to the right cycle, the transport layer header incorporates a kind of address called service point address or port address. Subsequently, by indicating this address, the physical layer ensures that the message is conveyed to the right cycle.
  • Provides reliable data transfer services to upper layer. This reliability is ensured through processes of Segmentation and Desegmentation.
  • Keep track of segments and retransmit those that fails.
  • The transport layer provides the acknowledgement for successful data transmission or the errors occurred.

5. Session Layer

  • The layer permits the two cycles to layout, use and ends a connection.
  • This layer permits an interaction to add designated spots which are viewed as synchronization focuses into the information. These synchronization guides help to distinguish the mistake so the information is re-synchronized appropriately, and closures of the messages are not cut rashly and information misfortune is kept away from.
  • Session’s layer is commonly implemented in application environments that uses remote procedure call (Software protocol).
  • This layer establishes check-pointing, adjournment, termination and restart procedures.

6. Presentation Layer

  • Information encryption makes an interpretation of the information into another structure or code. The encrypted information is known as the cipher text and the decoded information is known as plain text. A key worth is utilized for encrypting as well as decrypting information
  • Diminishes the number of bits that should be communicated to the organization
  • This layer is responsible for Interoperability
  • Presentation layer is responsible for integrating all the formats into a standard format for efficient and effective communication.
  • This layer deals with the syntax and semantics (Computer code language)
  • This method deals with string representation (Choosing pascal method or C++ language)
  • This layer makes data readable.

7. Application Layer

  • Network Virtual Terminal
  • File transfer access and management
  • Mail Services
  • Directory Services
  • This is the last layer which directly interacts with the user as well as the software application that implements the communication component.
  • This layer determines the identity and availability of communication partners for application with an efficient data to transmit.
  • This Layer handles Network transparency and resource allocation.
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