ABSTRACT
The Data Link Layer defines the protocol for data transmission across the Physical Layer. In the case of Ethernet a unique MAC (Media Access Con-
trol) address is provided for each device in order that data packets on the physical connection can be processed by the target device. CSMA/CD (Carrier Sense Multiple Access/Collision
Detect) provides packet management at the physical level. CSMA is a process for preventing a device accessing the network whilst another device is using the network. CD provides a process for managing the transmission when CSMA fails(!).
