Data Link Layer

The data link layer is responsible for hop-to-hop delivery. This layer combines the bits into manageable units called frames and delivers the frames to the next hop. In some protocols, it also transforms the physical layer, a rawtransmission facility, into a reliable link; it makes the physical layer appear error-free to the upper layer.

Some protocols divide the dat link layer into two sublayers: media access control sublayer and logical link control sublayer. In this case, the first three responsibilities belong to the logical link control sublayer.