Back to glossary

Transport Layer

The fourth layer of the OSI model, responsible for end-to-end communication, error recovery, and flow control.

Categorynetwork

Overview

The Transport Layer (Layer 4) ensures that messages are delivered error-free, in sequence, and with no losses or duplications. It provides transparent transfer of data between end users.

Key Protocols

  • TCP (Transmission Control Protocol): Connection-oriented, reliable delivery with error checking and flow control.
  • UDP (User Datagram Protocol): Connectionless, 'best-effort' delivery with low overhead, ideal for real-time applications.

Key Functions

  • Segmentation: Breaking application data into smaller segments.
  • Port Addressing: Using port numbers to direct data to the correct application.
  • Connection Management: Establishing and terminating connections (in TCP).

Related Terms

OSI ModelTCPUDPPort Number