The data link layer (layer 2) establishes the communications link between individual devices over a physical link or channel. It also ensures that messages are delivered to the proper device and translates the messages from layers above into bits for the physical layer (layer 1) to transmit. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page 83).