What is Logical Link Control (LLC)?
Logical Link Control (LLC) is a crucial component of the data communication protocol stack. It operates at the Data Link Layer of the OSI (Open Systems Interconnection) model, providing a reliable and error-free transmission of data between network devices.
LLC is responsible for establishing and maintaining a logical connection between the sender and receiver over a physical communication link. It ensures that data packets are correctly routed, reassembled, and error-checked before being passed to higher layers of the protocol stack.
One of the primary functions of LLC is to provide flow control and error control mechanisms. Flow control ensures that data is not transmitted faster than the receiving device can process. By maintaining a proper flow of data, LLC prevents congestion and optimizes the efficiency of data transmission.
Error control is another significant aspect of LLC. It uses various error detection and correction techniques to ensure data integrity during transmission. This involves adding error detection codes, such as cyclic redundancy check (CRC), to data packets. By detecting and correcting errors, LLC guarantees that the received data matches the transmitted data.
The LLC protocol can operate in two different types of service modes, known as connection-mode and connectionless-mode. In the connection-mode, data transmission occurs over a predefined connection, similar to a telephone call. On the other hand, connectionless-mode allows data packets to be transmitted independently without establishing a dedicated connection.
LLC is closely associated with the Media Access Control (MAC) sublayer, forming the Data Link Layer of the OSI model. While MAC is responsible for the physical transmission of data between devices, LLC adds an additional layer of control and reliability to ensure efficient communication.
In summary, Logical Link Control (LLC) plays a vital role in data communication by providing flow control, error control, and logical connection establishment. It enhances the reliability and efficiency of data transmission, enabling seamless communication between network devices.
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