This node explains how your actual Network Interface Card (NIC) performs its function. Let us assume that you have a file that you would like to send to a different computer on your Ethernet network.
Your application program generates the data you would like to send to the other computer. Your NIC accepts the data from your motherboard and transfers it to a small buffer. The NIC adds its own address (as set by the manufacturer), the destination address and the type of data to the buffer. Your NIC calculates the checksum, or CRC, for the data in the buffer. The information is arranged into a frame. Refer to Ethernet Frame for the exact specifications and the order of information in the frame. The NIC listens to the network for other transmissions. If a transmission is heard, it will wait until the transmission is complete. The NIC begins to serially transmit the Ethernet Frame over the network. The receiving NIC calculates the checksum for the received frame, then compares it to the checksum it received. If there are no errors, the receiving station acknowledges the received data.
NIC cards have many similarities. The major differences are the way the data is converted to transmit over the network. Each type of network has its own type of transceiver, or combination transmitter+receiver. 10baseT Ethernet networks have a specialized transceiver that translates the data into 10baseT Ethernet standards, then transmits it. It also receives information from the network and translates it back into a form the NIC card can use. 10base2 Ethernet networks have almost the same NIC except for the transceiver. Some NICs have two transceivers, normally 10baseT and 10base2. The rest of the NIC is used for both transceivers. These dual type cards are also known as combo NICs.
For additional information, refer to Ethernet frames and network topologies.
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