Which protocol operates at the Transport Layer (Layer 4) of the OSI model?

The Transmission Control Protocol (TCP) operates at the Transport Layer (Layer 4) of the OSI model. This layer is responsible for ensuring reliable data transmission between systems, segmenting data into manageable packets, and providing error detection and correction capabilities. TCP is well-known for its connection-oriented communication, which establishes a connection before data is sent and ensures that packets are delivered in the correct order and without errors.

In contrast, Hypertext Transfer Protocol (HTTP) operates at the Application Layer (Layer 7), which is responsible for the user interface and application services. The Internet Protocol (IP) operates at the Network Layer (Layer 3), focusing on routing and addressing packets between devices on a network. Address Resolution Protocol (ARP) functions at a lower layer, primarily interfacing between Layer 2 (Data Link Layer) and Layer 3, translating IP addresses into physical machine (MAC) addresses within a local network.

Understanding these distinctions within the OSI model is essential for grasping how different protocols function in data communication, particularly the critical role of TCP in ensuring reliable transport of data.