The Data Link Layer provides error detection and error recovery of the data flowing across the physical network link. The Specifications in this OSI Layer define network and protocol characteristics such as Physical addressing, network topology, error notification, flow control etc. The physical addressing defined in this layer determines how devices are addressed on the data link layer. An example of physical addressing is the MAC address which is hard-coded in all Ethernet Network Interface Cards (NIC). Each Ethernet NIC that exist in the world has a unique MAC address. The Data Link Layer also combines bits into Frames. Each Frame has a Layer 2 Header which includes the Source and Destination MAC addresses among other fields.
Examples of Layer 2 Specifications and Protocols
• IEEE 802.3 Ethernet
• Frame Relay