The checksum is computed by adding together the binary integers using bit arithmetic. The receiver recomputes the checksum and matches it with the checksum transmitted from the sender. Each computer attached to a LAN is assigned a unique numeric value known as its physical address . A shared network system uses physical addresses to filter incoming frames. Each LAN technology defines a frame format.
Most technologies have frames that consist of a header followed by data.
To inform the receiver about its contents, each frame contains additional information that specified the type of the contents. A network analyzer is a device that can be configured to count or display frames as they pass across a shared network. There are significant differences in the rate at which networks can operate and the CPUs processing speed. NICs handle all the details of packet transmission and reception without using the computer's CPU to handle each bit. The Ethernet wiring scheme is called Thick Ethernet or Thicknet since it uses a coaxial cable.