Which OSI layer is responsible for end-to-end communication control and segmentation?

• A. Network Layer
• B. Transport Layer
• C. Session Layer
• D. Data Link Layer

Answer: (B)

The capability to manage end-to-end communication control and break down data into transportable pieces lives in the Transport layer. It sits between the application-facing layers and the network, taking data from higher layers and organizing it into segments (or datagrams for some services). It handles sequencing, error detection and recovery, and flow control to ensure reliable delivery from the sending process to the receiving process, even across multiple networks. Protocols like TCP exemplify this by providing a reliable, connection-oriented service with guaranteed order and error checking, while UDP offers a lighter, connectionless alternative without those guarantees. The other layers don’t provide this end-to-end reliability and segmentation role: the Network layer focuses on routing and addressing across networks, the Session layer manages dialogue and synchronization between applications, and the Data Link layer handles framing, error detection on a single link, and physical addressing.