2. Data Link Layer

            The data link layer establishes and terminates a connection between two physically-connected nodes on a network. It breaks up packets into frames and sends them from source to destination.

Data Link Layer is divided into two sub layers :  

1. Logical Link Control (LLC)

2. Media Access Control (MAC)

          Logical Link Control (LLC), which identifies network protocols, performs error checking and synchronizes frames, and Media Access Control (MAC) which uses MAC addresses to connect devices and define permissions to transmit and receive data.

1. Packet in Data Link layer is referred as Frame. 

2. Data Link layer is handled by the NIC (Network Interface Card) and device drivers of host machines. 

3. Switch & Bridge are Data Link Layer devices.