Which function is a key responsibility of the data link layer in Ethernet networks?

• A. Providing framing, addressing, and error detection
• B. Routing packets between networks
• C. Encrypting data for security
• D. Managing end-to-end connections

Answer: (A)

The data link layer in Ethernet is responsible for turning network-layer packets into frames that can be transmitted over a local link, and for ensuring those frames are properly addressed and checked for errors. In Ethernet, each frame carries a header with destination and source MAC addresses so the frame can be delivered to the correct device on the same network segment, and a trailer containing a frame check sequence (CRC) so receiving devices can detect any bit errors that occurred during transmission. This layer also defines how access to the shared medium is managed and how frames are formed and parsed, with the MAC sublayer handling addressing on the local link.

Routing between networks is handled by the network layer, not the data link layer. Encryption and security are not fundamental responsibilities of the data link layer, though some link-level security features can exist. End-to-end connection management is a transport-layer role, not a data link-layer one.