NETWORK ACCESS LAYER

The network access layer (Data Link + Physical layers of OSI) relates the internet software layer to the hardware that carries the data, and it is the lowest layer in the DoD data communications model. The key point to understand is that network numbers are not understood at this layer; the addresses used at the network access layer have significance only for the network segment on which the packet is transmitted. The addresses at the Network Access layer do not transverse a router.

The network access layer specifies the physical (hardware) medium for data transmission. The Institute of Electrical and Electronics Engineering (IEEE) Project 802 established standards that define interface and protocol specifications for various network topologies. The Data Link layer (OSI model) is split into two: the Logical Link Control (LLC) sub layer, and the media access Control (MAC) sub layer. The LLC sub layer defines how a receiving machine discards damaged packets. The Mac sub layer handles issues of supplying globally unique hardware addresses to device interfaces.