Model ISO - OSI

What is ISO OSI model

ISO OSI = International Organization for Standardization Open Systems Interconnection

ISO OSI model is conceptual framework:

  • used to standardize and understand how different networking protocols and functions interact within a networks
  • consists of seven layers, each with a specific role and set of functions


Physical Layer (Layer 1):

  • the lowest layer
  • deals with the physical aspects of data transmission.
  • defines the physical medium, such as cables, electrical voltages, or optical signals, and how data is transmitted over them.
  • example: Ethernet cables, fiber optic connections, and wireless communication signals.
  • responsible for framing data for transmission and detecting and correcting errors in the data
  • manages access to the physical medium
  • resolves issues related to the physical addressing of devices on a local network.
  • examples: Ethernet and Wi-Fi

Network Layer (Layer 3):

  • focuses on routing and forwarding data between different networks or subnets.
  • uses logical addressing (such as IP addresses) to determine the best path for data to travel from source to destination
  • exampkes: routers operate at this layer

Transport Layer (Layer 4):

  • manages end-to-end communication and data segmentation into smaller packets.
  • provides error detection, flow control, and data integrity, ensuring that data is reliably and accurately delivered
  • examples: Protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)

Session Layer (Layer 5):

  • establishes, maintains, and terminates connections between two devices or applications
  • manages session synchronization and ensures that data is delivered in the correct order
  • examples: NetBIOS and RPC (Remote Procedure Call)

Presentation Layer (Layer 6):

  • responsible for data translation, encryption, and compression.
  • ensures that data is in a format that both the sender and receiver can understand.
  • can handle data compression and encryption as needed.

Application Layer (Layer 7):

  • the topmost layer, the closest to end-users and applications
  • provides network services directly to end-users and applications (usually through language or libraryAPI) and is where most user-facing software interacts with the network
  • Common application layer protocols include HTTP (for web browsing), SMTP (for email), and FTP (for file transfer)