Networking

Question 1

Describe the OSI Model layers

Answer 1

The OSI Model is a fundamental framework for understanding how network interactions occur. It comprises 7 distinct layers, each with it’s own roles & responsibilities, working together to facilitate communication across systems & devices.

• Application layer (L7)
  Interfaces directly with end user applications to provide network services. It manages application-level protocols like http, ftp, SMTP, which enable services such as web browsing and email.
• Presentation Layer (L6)
  Translates data between network and application formats. It manages data encryption, compression and formatting. It maintains system interoperability by ensuring data is readable by both sender and recipient.
• Session Layer (L5)
  This layer manages the creation, maintenance and termination of communication sessions between applications for efficient data transfer. Supports full-duplex and half-duplex communication to ensure proper sequencing and coordination in multi way exchanges.
• Transport Layer (L4)
  It coordinates end to end communication by delivering data to the correct application through ports, using either reliable delivery (TCP) or unreliable but faster methods (UDP). Error checking, flow control, and segmentation are used in the transport layer to achieve reliable data transfer.
• Network Layer (L3)
  Handles data routing, forwarding and addressing, determining the optimal path for data to reach it’s destinations using protocols like IP and ICMP.
• Data link layer (L2)
  Facilitates reliable data transfer across physical network links. Provides error detection and correction. Manages how data is placed onto the network medium. Uses protocols like ethernet and PPP.
• Physical layer (L1)
  This layer forms the foundation of the OSI model, converting raw bitstreams into signals for transmission over physical media. It defines the hardware specs for transmission, including the types of physicial media that can be used, such as cables and data rates.

The OSI model is grounded in principles that support structured and predictable data movement.
Each layer operates independently, simplifying design and troubleshooting. Data is encapsulated with headers as it moves down the layers and decapsulated as it ascends, preserving information integrity.

By standardising communication, this framework promotes system interoperability and supports global data exchange.