#The data link layer provides data sending and receiving functions for network layer entities.
The data link layer is the second layer in the OSI reference model, between the physical layer and the network layer. The data link layer provides services to the network layer based on the services provided by the physical layer. Its most basic service is to reliably transmit data from the network layer to the target network layer of adjacent nodes.
The data link layer mainly has two functions: frame coding and error correction control. Frame encoding means defining a data packet that contains information frequency, bit synchronization, source address, destination address, and other control information. The data link layer protocol is divided into two sub-layers: Logical Link Control (LLC) protocol and Media Access Control (MAC) protocol.
The most basic function of the data link layer is to provide transparent and reliable basic data transmission services to users of this layer. Transparency means that there are no restrictions on the content, format, and encoding of data transmitted on this layer, and there is no need to explain the meaning of the information structure; reliable transmission eliminates users' worries about lost information, interfering information, and incorrect order.
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