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Data Link Layer


Data link Layer(Layer 2): It makes the raw transmission facility, reliable and error-free to the upper layer. It is responsible for moving the frames from one hop to the next, reliable transmission of data frames between two nodes connected by a physical layer.
Functions include:




  • Framing: This layer divides the stream of bits from the network layer and organizes into manageable data units called frames.
  • Physical Addressing: The data link layer adds a header to the frame in order to define physical address of the sender or receiver of the frame, if the frames are to be distributed to the different systems on the network.
  • Flow Control: If the data rate, at which the data is transmitted by the sender is greater than the rate at which data is received by the receiver, this layer imposes a flow control mechanism to prevent overwhelming the receiver. This prevents traffic jam at the receiver side.
  • Error Control: This layer adds reliability to the physical layer by adding mechanisms to detect and retransmit damaged or lost frames and to prevent duplication of frames.
  • Access Control: When two or more devices are connected to the same link, data link layers are necessary to determine which layer has control over the link at a given time.
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