Network Interface Card (NIC)

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Definition of Network Interface card (NIC) in Network Encyclopedia.

What is Network Interface Card?

NIC stands for Network Interface Card is an adapter card that plugs into the system bus of a computer and allows the computer to send and receive signals on a network. A network interface card (NIC) is also known as a network adapter card or simply a network card.

NIC - Network Interface Card
NIC – Network Interface Card

How It Works

NICs can be legacy components that require manual configuration of interrupt request (IRQ) and base I/O port settings, or they can be plug and play components. NICs are available for any system bus type: Industry Standard Architecture (ISA), Extended Industry Standard Architecture (EISA), Micro Channel Architecture, and Peripheral Component Interconnect (PCI). PCI cards are 32-bit and give the best performance. They are available in various speeds, such as 10 Mbps for Ethernet and 10/100 Mbps for Fast Ethernet. Other cards are available for networking technologies such as Token Ring and Fiber Distributed Data Interface (FDDI).

A computer can communicate with the NIC using several methods, including memory-mapped I/O, direct memory access (DMA), or shared memory. A parallel stream of data is sent to the card and buffered before being packaged into discrete frames for serial transmission over the network. Framing adds headers and trailers to the data, which contains addressing, clocking, and error-checking information. The frames are then converted to electrical voltage pulses that drive an electrical signal over the wire. The receiving NIC processes the signal in the reverse order into a data stream for the receiving computer. Many of these functions are built into the network firmware, while others are governed by the NIC driver software installed on the computer.

Motherboard with two network interface adapters (RJ-45)
Motherboard with two network interface adapters (RJ-45)

The most widely used network connection for personal computers is an Ethernet connection. Ethernet is really a standard for computer network technologies that describes both hardware and communication protocols. Ethernet was commercially introduced in 1980 and has largely replaced other wired network technologies.

Since Ethernet is so widely used, most modern computers have a NIC built into the motherboard. A separate network card is not required unless some other type of network is used. Here, you can see an Ethernet connection built into a motherboard. Several other connections are located directly adjacent to the Ethernet connection.

An Ethernet connection uses a standard interface known as an RJ45 connector. ‘RJ’ stands for ‘registered jack.’

RJ-45 Connector - most widely used connect to Network Interface Cards
RJ-45 Connector – most widely used connect to Network Interface Cards

This cable plugs into the Ethernet connection of a computer. Small LED lights built into the connection will show that a connection is active and whether data is being transferred.