network interface card (NIC)

What is a network interface card (NIC)?

A network interface card (NIC) is a hardware component, typically a circuit board or chip, which is installed on a computer so it can connect to a network. Modern NICs provide functionality to computers, such as support for I/O interrupt, direct memory access (DMA) interfaces, data transmission, network traffic engineering and partitioning.

A NIC provides a computer with a dedicated, full-time connection to a network. It implements the physical layer circuitry necessary for communicating with a data link layer standard, such as Ethernet or Wi-Fi. Each card represents a device and can prepare, transmit and control the flow of data on the network.

The NIC uses the OSI model to send signals at the physical layer, transmit data packets at the network layer and operate as an interface at the TCP/IP layer.

OSI model diagram
The NIC performs different functions for different layers of the OSI model.

The network card operates as a middleman between a computer and a data network. For example, when a user requests a webpage, the computer will pass the request to the network card, which converts it into electrical impulses.

A web server on the internet receives the impulses and responds by sending the webpage back to the network card as electrical signals. The card gets these signals and translates them into the data that the computer displays.

Originally, network controllers were implemented as expansion cards that could be plugged into a computer port, router or USB device. However, more modern controllers are built directly into the computer motherboard chipset. Expansion card NICs can be purchased online or in retail stores if additional independent network connections are needed. When purchasing a NIC, specifications should correspond with the standard of the network.

The term network interface card is often considered interchangeable with the terms network interface controller, network adapter and LAN adapter.

Types of network interface cards

While the standard NIC is a plastic circuit board that slides into a computer to connect with the motherboard, there are multiple ways this connection can occur:

  • Wireless. These are NICs that use an antenna to provide wireless reception through radio frequency waves. Wireless NICs are designed for Wi-Fi connections.
  • Wired. These are NICs that have input jacks made for cables. The most popular wired LAN technology is Ethernet.
  • USB. These are NICs that provide network connections through a device plugged into the USB port.
  • Fiber optics. These are expensive and more complex NICs that are used as a high-speed support system for network traffic handling on server computers. This support could also be accomplished by combining multiple NICs.

Components of network interface cards

Network interface card components include the following:

  • Speed. All NICs have a speed rating in terms of Mbps that suggests the general performance of the card when implemented in a computer network with ample bandwidth. If the bandwidth is lower than the NIC or multiple computers are connected with the same controller, the labeled speed will be slowed down. The average Ethernet NICs come in 10 Mbps, 100 Mbps, 1000 Mbps and 1 Gbps varieties.
  • Driver. This is the required software that passes data between the computer's operating system (OS) and the NIC. When a NIC is installed on a computer, the corresponding driver software is also downloaded. Drivers must stay updated and uncorrupted to ensure optimal performance from the NIC.
  • MAC address. Unique, unchangeable MAC addresses, also known as physical network addresses, are assigned to NICs. These are used to deliver Ethernet packets to the computer.
  • Connectivity LED. Most NICs have an LED indicator integrated into the connector to notify the user of when the network is connected and data is being transmitted.
  • Router. A router is also sometimes needed to enable communication between a computer and other devices. In this case, the NIC connects to the router which is connected to the internet.
This was last updated in October 2021

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