IP SANs: A Guide to iSCSI, iFCP, and FCIP Protocols for Storage Area Networks

5.1. Layer 2

The OSI Reference Model defines the physical, data link, and network layers as the foundation strata on which higher level functions are built. The physical and data link layers are mandatory for communication between any two devices on the same network segment. A local LAN, for example, may use twisted pair cabling to join three workstations, each provisioned with an adapter card. Copper wire provides the physical layer function, whereas the NICs provide the data link functions. As shown in Figure 5-1, these two layers alone are, theoretically, sufficient for communication between the workstations. Logical link control oversees the orderly transmission of data from the upper layer application to the underlying MAC layer. The MAC ...