Overview
This lecture compares different network layer models, emphasizing the widely used five-layer model and the more detailed seven-layer OSI model.
Network Layer Models
- There are multiple network layer models used in IT, not just one standard.
- The five-layer model is commonly used in practical networking contexts.
- Some models combine the physical and data link layers, resulting in a four-layer model.
OSI Model
- The OSI (Open Systems Interconnection) Model contains seven layers, making it more detailed than the five-layer model.
- The OSI model is often used in academic and certification settings for its rigorous definitions.
- The session layer (layer 5) manages communication between applications and the transport layer.
- The presentation layer (layer 6) ensures data from lower layers is formatted and understood by applications, often handling encryption and compression.
- These extra layers don't involve data encapsulation like the lower layers do.
Comparison of Models
- The five-layer model combines the session and presentation layer functions into its application layer.
- While the five-layer model is more practical for daily networking tasks, understanding the OSI model is important for a complete networking education.
Key Terms & Definitions
- OSI Model — A seven-layer networking model used for standardizing network functions.
- Session Layer — OSI layer that manages communication sessions between applications and the transport layer.
- Presentation Layer — OSI layer responsible for data formatting, encryption, and compression for application understanding.
- Application Layer (in five-layer model) — Handles all higher-level networking functions, including those managed by session and presentation in OSI.
Action Items / Next Steps
- Review the reading section on the OSI model from Module 1.