What is an Ethernet Network Adapter?

An Ethernet Network Adapter is a hardware device used to connect a computer to a local area network (LAN). Sometimes called a network interface card (NIC), an Ethernet network adapter supports Ethernet standards for high-speed networking over cables. The primary function of this device is to transmit and receive data to and from a network hub, switch, or router.

Most computers come with a built-in Ethernet network adapter. Those that do not can have one added. This can be done by installing an adapter card inside a computer using a PCI slot on the motherboard. Another option is to attach an Ethernet network adapter using a computer's serial or USB port.

Ethernet network adapters are characterized by their data transmission speeds. Desktop and notebook computers today typically use either a Fast Ethernet or Gigabit Ethernet adapter. These adapters support transmission rates of 100 Megabits per second and 1 Gigabit per second, respectively. High performance workstations and servers typically use 1 Gigabit per second Ethernet network adapters.

Every Ethernet network adapter has a jack that accepts a cable, which carries the data. The cable connects a computer to networking hub, switch, or router. The cable may be made of copper wires or fiber optic cables; typically, fiber optic Ethernet network adapters are only used in special cases. For example, a fiber optic adapter would be used when a cable passes an area where there is lots of electrical interference. Fiber optic adapters are also used when the computer is very far away from the hub or switch.

To send and receive data, an Ethernet network adapter works in conjunction with networking and driver software. For outgoing data, the adapter parses large blocks or streams of data into small chunks. It then places these small chunks of data into packets, called Ethernet frames. Each Ethernet frame has a header with information about the destination and source address. The destination information is used by networking equipment to direct the packet to recipient's computer.

A second part of the Ethernet frame is the payload, which is essentially the small chunk of raw data. The last element of the Ethernet frame is a small amount of data called a CRC Checksum. The CRC Checksum is used to ensure the data has not been corrupted in the transmission.

With incoming data, an Ethernet network adapter again works with driver and networking software. In this case, the adapter extracts the payload data from the incoming Ethernet frames.

New uses of Ethernet network adapters continue to emerge. For example, many company phone systems are being replaced by voice over IP (VoIP) systems where phone calls are carried over the company data network or the Internet. The VoIP handsets at each person's desk include an Ethernet network adapter, and the phones are connected using Ethernet cabling instead of a phone cord.