The transport layer is responsible for reliable data delivery between devices across a network.
- It ensures that data is efficiently transferred, managed, and delivered accurately to the correct application.
The key functions of the transport layer include:
1.) Linking to the Application Layer
- The transport layer acts as an interface between the application layer and the network.
- It ensures data is passed to the appropriate application or process on the receiving device.
Mechanism:
- The transport layer uses port numbers to identify different applications or services (e.g., HTTP uses port 80, HTTPS uses port 443).
Example: A web browser uses the transport layer to connect to a web server via HTTP, ensuring the correct application is communicated with.
2.) Segmenting
Segmenting involves breaking large data streams from the application layer into smaller, manageable pieces called segments.
- Prevents data congestion in the network.
- Ensures proper reassembly at the receiving end.
Mechanism:
- Each segment is labeled with sequence numbers for proper ordering and reassembly.
- Example: A file sent over the network is divided into smaller packets for transmission and reassembled on the receiver’s end.
3.) Session Management
The transport layer establishes, maintains, and terminates communication sessions between devices.
- Provides reliability and ensures the communication session persists as long as needed.
- Manages flow control and error correction during the session.
Mechanism:
- Uses protocols like TCP (Transmission Control Protocol) to create a reliable connection-oriented session.
- Acknowledges successful data receipt and retransmits if needed.
- Example: A video streaming session maintains smooth playback by managing packet delivery and ensuring packets arrive in order.
