Updated March 28, 2023
Introduction to Data Link Layer OSI Model
The data link layer comes in the second position in the Open System Interconnection(OSI) reference model. The data link layer lies over the physical layer. In the data link layer, the data connection is established between two network nodes in which the connection is maintained for the data transfer. The connection can be created, maintained or can be released using the data link layer. There can be a different type of physical lines in between data-link connection includes optical cable, copper wire, satellite channel, and microwave link. In the data link layer, the data packets are received from the network layer and then these packets convert to frame which is forwarded to the physical layer. The data synchronization is carried in a data link layer. The other features supported by the data link layer are error synchronization, data encoding which is transmitted to the physical layer. Error control is also done in the data link layer. The duplication of frames can be identified by the help pf error control. The error control is added to the tail of the frame to remove frame duplicity.
The Open Systems Interconnection (OSI) model is the reference type of model which is used for the applications that how they interact with the network. The OSI model has seven different layers. These layers can be used for defining the framework and can be used for interacting with a network. The layers include the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. The OSI model is used for understanding the architecture of the network and based on that, the telecommunication products can be designed by taking reference from it.
Functions in the Data link layer in the OSI model
Every OSI model layer is designed for performing some function. The data layer functions are described below:
- In the data link layer, the data is received from the upper layer that is network layer and the received data is converted to frames by the data link layer.
- After converting it to frame, the header is added to each frame for providing the addressing information to frames. Each frame contains the address of the source computer and the destination computer. In the framing process, the control information is additionally added to identify the starting end and ending end of the data frame so that it can be easily transmitted to the physical layer.
- The other functionality of the data link layer is to control the flow of data transmission. The flow is maintained by the transmitter as there is some disbalance between receiving the data and sending the data. The rate is not the same which creates a problem of traffic management in the data link layer.
- The data link layer provides the functionality of data reliability for the physical layer. In the data link layer the duplicate frame, damaged frame, and incomplete frame are differentiated from the correct frame which provides data reliability and only correct frames are forwarded to the physical layer.
- The access control mechanism is also provided by the data link layer. When there is more than one device is connected to the network having the same link, the protocol is used to maintain access for a different device that is connected.
- The other functionality is the framing of large size data packets. Whenever the data link layer received a large size of data from the network layer the framing is done on data in which the small frames are created from a large stream of data. This process is known as framing or data segmentation. By this, the transmission of these frames became easy and can be easily transmitted to the physical layer. The large size of data frames has always a risk of frame corruption which can create an issue of data reliability in the physical layer.
- The other important function of the data link layer is error control. In the error control mechanism, the error control is added to the end of the frame. By this, the receiving end is checked and if the error control value is the same it implies that the packet is not corrupted. The error control also helps to find out the duplicate frames. And also to remove the corrupted error and to prevent them from forwarding to the physical layer.
Design issue in Data layer in OSI model
There are always some pros and cons for each type of layer in the OSI model. The design issues related to the data link layer are described below:
- The main design issue is to maintain a transmitter that is of high processing speed so that it can maintain a balance between slow receiving data end. The data link layer lacks in having a traffic control mechanism that can be used to track buffer space at the receiving end.
- The other design issue in the data link layer is to maintain proper access to the channel which needs to be shared over the network.
- The third issue in the data link layer is to track the number of packets that are routed between the source end and destination end. These can be done by maintaining static tables that do not change often.
- The quality of frames which are created from the data received from the network layer.
- The other data link layer issue is to maintain the flow of packets and deal with the transmission error issues.
Conclusion
All the layers of the OSI model have some functionality that is used to communicate with the network. Every telecommunication layer uses the OSI model to interact with the network. The data transmission is controlled using the OSI model and also the flow of data is maintained using the OSI model and to maintain the communication between the two network nodes which are placed in the network.
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