Which OSI layer is involved in providing end-to-end delivery of data streams with error checking and flow control?

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

Answer: (B)

The transport layer handles end-to-end delivery of data streams with reliability mechanisms. It establishes logical connections between endpoints, breaks data into segments, and ensures those segments are delivered correctly and in order. It uses error checking and retransmission as needed, and implements flow control to prevent the sender from overwhelming the receiver (for example, via windowing in TCP). This is what provides reliable, end-to-end communication across multiple networks.

The data link layer only checks errors on a single link between two devices, not across the entire path. The network layer is responsible for routing and addressing, not ensuring end-to-end reliability. The application layer deals with user-facing services and data formats, not transport reliability.