What is the data link layer and what services does it provide?

The data link layer is responsible for transferring datagramsdata packets having source and destination MAC addresses from one node to another node connected by the same link.

Services provided by the link layer

Framing and addressing:

• Encapsulates a datagram into a frame, adding a header
• Uses “MAC” addresses in frame headers to identify the source & destination

Error detection

• Checks for corruption of data by bits being changed and provides a mechanism for data recovery by dropping frames or signaling for retransmission

Flow control:

• Provide equal speed of access for data exchange, even while the actual link speeds for different links may be different

Half-duplex and full-duplex communication:

• In half-duplex, the nodes at ends can each transmit data, but not simultaneously.
• In full-duplex form, nodes at either end can transmit the datagrams simultaneously.