AP Networking Practice Test

Reliability on the local link is the job of the Data Link Layer. It takes the raw data from the Network Layer and packages it into frames with local addressing (MAC addresses) and error-detection information (like a CRC). The receiving device checks the frame for errors; if the data is intact, it passes it up to the Network Layer. If an error is detected, the frame is typically discarded, and higher-layer protocols handle any necessary retransmission on that single link. This focus on delivering data between directly connected devices with error checking distinguishes it from the other layers: the Network Layer routes data across multiple networks, the Transport Layer provides end-to-end reliability across those networks, and the Physical Layer merely transmits the raw bits. So, this description matches the Data Link Layer.