What is a Data Link Layer?

Data Link Layer is the second layer in the OSI reference model. It represents creating a shared transmission medium and frequent transmission of the data frame in a computer transmission setting.

It obtains a natural flow of items for the physical layer at the sender device. The primary stream of data is generated using different technologies like cable, DSL, wireless, optical fibre, etc.

Service Provided to Network Layer 

The data link layer supports well-defined interfaces to the network layer. It can manage communication errors, control the data flow, and manage sender and receiver inconsistency by keeping the multiple services.

The data link layer works these actions in the following method −

Unacknowledged connectionless service

This contains separate frames from the source host to the destination host without some acknowledgement structure. It does not have any link established or launched. It does not manage with frame recovery because of medium noise.

Acknowledged connectionless service

The transmission medium is more error-prone. This needs acceptance service for each frame transmitted between two hosts to provide that the frame has appeared perfectly.

Acknowledged connection-oriented service

This layer supports this service to the network layer by settling a link between the source and destination hosts before any information removal occurs.


In this layer, it gets a raw bitstream from the physical layer that cannot be error-free. The data link layer breaks the bitstreams into frames to support a frequent change of bitstreams to the network layer.

Error Control

It contains sequencing frames and transmitting control frames for acceptance. A noisy medium can prevent scanning of bits, falling bits from a frame, entering unique bits in the frame, frames final sinking, etc.

Flow Control

There is another fundamental problem in the data link design to regulate the cost of data communication between two source and destination hosts. If the conflict between the source and destination hosts information sending and receiving speed, it will generate packets to drop at the receiver end.

Sequence Integrity

The data link layer maintains the data bits sequence and sends them to the physical layer in the same series as received from the network layer. It provides a reliable transfer of data link service data unit (DLSDU) over the data link connections.