๐ Introduction to the Transport Layer
The Transport Layer in the OSI model is responsible for end-to-end communication between devices. It ensures that data is transferred reliably and efficiently across the network, providing services such as:
- Connection-oriented communication (TCP)
- Connectionless communication (UDP)
๐ท Transport-Layer Services
Key services provided by the transport layer:
- Port Addressing: Identifies different processes running on the same device using port numbers (e.g., port 80 for HTTP).
- Socket Addressing: Combination of an IP address and a port number to uniquely identify a connection.
- Flow Control: Manages the rate of data transmission to prevent congestion.
- Error Detection and Recovery: Ensures data integrity through checksums and retransmission (in TCP).
- Multiplexing: Enables multiple applications to use the network concurrently through different ports.
๐ Port and Socket Addresses
- Port Address: A 16-bit number (0-65535) used to identify the sending/receiving process on a device. Ports 0-1023 are reserved for well-known services.
- Socket Address: A combination of an IP address and a port number (e.g., 192.168.1.1:80).
๐ Real-world Example
- HTTP Request (TCP): A client communicates with a web server on port 80 to request a page, and the transport layer ensures that the data reaches the right application by utilizing the correct socket address.
๐ง Insights
- The transport layer is critical for managing communication between networked applications, ensuring reliability (TCP) or low overhead (UDP) depending on application needs.