OSI Reference Model

OSI Reference Model

In the beginning, when networks established, devices can communicate with devices of the same manufacturer.OSI (open system interconnection) reference model was first introduced by ISO (international organization for standardization).Its main purpose is to facilitate communication between two systems of the different manufacturer.It is conceptual structure.It is a concept that how communication should take place.It consists of seven layers.When a communication system is designed by following these seven layers architecture, then it is called a layered architecture.

We use a sentence to remember these layers.

All People Seem To Need Data Processing 

Youtube

I have already discussed OSI layer introduction.Now This video will provide some advance concepts.

 Application Layer

It provides services to the user application to communicate over the internet.Provides access to network resources.It deals with network applications such as

  • Mail
  • Web
  • File transfer
  • Internet browsing using HTTP
  • File transfer in remote computer using FTP
  • Email services using SMTP
  • etc

Presentation Layer

It ensure that data transfer from the application layer of one system is readable by the application layer of the second system

  • Data translation (Alphabet, numbers into bits)
  • Compression and decompression
  • Encryption and decryption

Session Layer

  • Establish   (Dialog )
  • Security and access control
  • Duplexing (half, full)
  • End connection

Transport Layer

  • Process to process delivery
  • Port addressing
  • TCP and UDP(reliable and unreliable communication)
  • Segmentation and reassembly
  • Flow control
  • Error control
  • Segment

Network Layer

  • Source to destination delivery (end to end)
  • Logical addressing ( IP address )
  • Routing
  • packet

Data Link Layer

  • Divide message into pieces called frame
  • Delivery of data from one device to another device on a LAN using hardware address
  • Error control,flow control
  • Physical addressing (MAC = Medium access control)
  • Frame

Physical Layer

All these layers are logically separated in a system.You can not physically find any distribution in any system.

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