Data Link Layer of the OSI Model

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Data Link Layer of the OSI Model Data link layer is the second layer of the OSI model. It handles data transfer between network and the physical layers of the OSI Model. Data unit at the data link layer is called as frame. Data link layer receives data f

Data Link Layer of the OSI Model

Data link layer is the second layer of the OSI model. It handles data transfer between network and the physical layers of the OSI Model. Data unit at the data link layer is called as frame. Data link layer receives data from network layer. It adds header and trailer to the data and passes data to the physical layer. At the receiver side, data link layer receives data from the physical layer. It detaches header and trailer from the data and passes data to the network layer.

Functioning of Data Link Layer

Responsibilities of the data link layer are:

Framing - The physical layer distributes raw bits from the source to destination. During transmission, the value of the bits can change. It is also possible that the number of bits received by the receiver may be different from the number of bits sent by the sender. To resolve this problem, the data link layer organizes the bits into manageable data units called as frames.

Physical Addressing - Data link layer adds header to the frame which contains the physical address of the sender and/or receiver. Headers are assigned when the frames are to be distributed to various systems within the network.

Access Control - When the devices in the network use the same link for communication, at a time only one device should transmit data. The data link layer provides access to a particular device to use the link at a given time.

Flow Control - It may happen that the speed at which the sending and receiving nodes operate may differ. The sending node may transmit data at a faster rate but the receiving node may receive it at a slower rate. The rate of data transmission between two nodes should be controlled to keep both the nodes in synchronization. This process is called flow control.

Error Control - Another function of the Data Link layer is error control. Error control detects and corrects errors. During transmission, if a frame is lost or corrupted, the data link layer retransmits that frame. It also prevents duplication of frames. Error control is accomplished using trailer at the end of the frame.

You may also be interested in understanding the other seven layers of the OSI Model

Application Layer of the OSI Model

Presentation Layer of the OSI Model

Session layer of the OSI Model

Transport Layer of the OSI Model

Network Layer of the OSI Model

Physical Layer of the OSI Model

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