What Is a Network Interface Card - NIC Definition, Function & Types

May 7, 2019

A network interface card (NIC or network adapter) is an important hardware component used to provide network connections for devices like computers, servers, etc. With its wide applications, there are various types of network interface cards emerging in the market like PCIe card and server network card. In this post, we will have a full exploration of this hardware component from what is a network interface card to its function, components, and types.

What Is a Network Interface Card?

Network interface card, also known as NIC or network interface controller, is typically a circuit board that installed on the computer to connect to the network. It works as an indispensable component for the network connection of computers. Currently, NIC cards designed as a built-in style are commonly found in most computers and some network servers. Besides, network cards like server network card can also be inserted into expansion slots of devices.

Figure 1: What is a network interface card- NIC definition

What Is the Function of Network Interface Card?

NIC definition is very simple, but what does a network interface card do and what is the function of NIC? Working as an interface at the TCP/IP layer, a NIC card can transmit signals at the physical layer and deliver data packets at the network layer. No matter what layer the network interface controller lies, it acts as a middleman between a computer/server and a data network. When a user requests a web page, the LAN card gets data from the user device, and sends them to the server on the internet, then receives the required data back from the Internet to display for users.

Components of Network Interface Card

Conventionally, a network adapter mainly consists of a controller, boot ROM socket, one or several NIC ports, a motherboard connection interface, LED indicators, a profile bracket, and some other electronic components. Every component of a LAN card has its unique function:

Controller: The controller is like a mini CPU, processing data received. As a core part of a network adapter, the controller directly decides the performance of the network adapter.

Boot ROM socket: This socket on the card enables boot ROM capability. Boot ROM allows diskless workstations to connect to the network, increasing security and lowering the cost of hardware.

NIC port for cable/transceiver: Usually, this port will connect with an Ethernet cable or transceiver directly, which can generate and receive the electronic signals that are put on the network cable or fiber cable.

Bus interface: This interface is on the side of the circuit board, which serves for the connection between the NIC and computer or server via being plugged into their expansion slot.

LED indicators: Indicators are used to help users to identify the working status of a network card whether the network is connected and data transmitted.

Profile bracket: There are two types of profile brackets in the market. One is called the full-height bracket with a length of 12 cm, and the other is the low-profile bracket with a length of 8 cm. This bracket can help users fix the NIC in the expansion slot of a computer or server.

Figure 2: Components of network interface card

Types of Network Interface Card

The network interface cards can be classified into different types on the basis of different features like host interface, transmission speed and application fields. The following part gives the details.

Network Connection Based Classifications

Based on the way a network card accessing the network, there are wired NIC and wireless NIC. As the name shows, a wired NIC usually has to connect a node onto a network with a cable like Ethernet cable and fiber optic cable. A wireless NIC card often comes with a small antenna, which uses radio waves to communicate with the access point to get involved in a wireless network.

Bus Interfaces Based Classifications

ISA (Industry Standard Architecture) network card: ISA bus was developed in 1981, which was a standard bus architecture for IBM compatibles. Due to the low card speed of 9Mbps, the ISA bus interface now is no longer a recognized type, and it’s hard to find it in today’s stores.

PCI (Peripheral Component Interconnect) network card: PCI bus was developed in 1990 to replace the previous ISA standard. It has a fixed width of 32 bit (133MB/s transmission data) and 64 bit (266MB/s transmission data). This type of NIC card was first used in servers and later on gradually applied to PCs. Today, most PCs do not have expansion cards, but rather devices integrated into the motherboard. As a result, PCI network card has been replaced by other bus interfaces, like PCI-X or USB interface.

PCI-X (Peripheral Component Interconnect eXtended) network card: PCI-X is an enhanced PCI bus technology. It operates at 64 bit and is capable of up to 1064 MB/s. In many cases, PCI-X is backward compatible with PCI NIC cards.

PCIe (Peripheral Component Interconnect Express) network card: PCIe is the latest standard and now is popular on computer and server motherboards. PCIe NIC card is available in five versions now, and each version supports five types of lanes at different speeds. Learn more about PCIe network card, read the post: What Is PCIe Card? Everything You Need to Know About PCI Express Card.

PCIe Version Line Code x1 x2 x4 x8 x16
1.0 8b/10b 250MB/s 0.50GB/s 1.0GB/s 2.0GB/s 4.0GB/s
2.0 8b/10b 500MB/s 1.0GB/s 2.0GB/s 4.0GB/s 8.0GB/s
3.0 128b/130b 984.6MB/s 1.97GB/s 3.94GB/s 7.88GB/s 15.8GB/s
4.0 128b/130b 1969MB/s 3.94GB/s 7.88GB/s 15.75GB/s 31.5GB/s
5.0 128b/130b 3938MB/s 6.15GB/s 12.3GB/s 24.6GB/s 63.02GB/s

USB (Universal Serial Bus) network interface card: USB bus is an external bus standard. It has three versions with different data rates and can work together with a variety of devices. In addition, the wireless network card is also a type of NIC card, which is designed for Wi-Fi connection.

Port Type Based Classifications

According to different cables connected, four types of NIC ports can be found in the market. RJ-45 port is used to connect with twisted pair cable (like Cat5 and Cat6), AUI port used for thick coaxial cable (like AUI transceiver cable), BNC port for thin coaxial cable (like BNC cable), and optical port for transceiver (like 10G/25G transceiver).

Transmission Speed Based Classifications

Based on different speeds, there are 10Mbps, 100Mbps, 10/100Mbps adaptive card, 1000Mbps, 10GbE, 25G or even higher speed network cards on the market. 10Mbps, 100Mbps and 10/100Mbps adaptive NIC cards are suitable for small LAN, home uses or day-to-day offices. 1000Mbps NIC provides a higher bandwidth in the Gigabit network. As for the 10Gb/25Gb NIC or even higher speed NIC cards, they are welcomed by the large enterprises or data centers. To know more about 25G NIC, you can read this post: 25G NIC - the Highly Effective Path Towards 100G Network.

Application Fields Based Classifications

Computer NIC card: Today, most new computers have the NIC built into the motherboard, so a separate LAN card is not needed. It commonly comes with 10/100Mbps, and 1Gbps speed, and allows one PC to communicate with other PCs or networks.

Server network card: The main function of a server network card is to manage and handle network traffic. Compared with the ordinary PC network adapter, server adapters usually requires faster data transmission speed like 10G, 25G, 40G, and even 100G. Plus, server adapters have low CPU occupancy rate, since it has a special network controller that can take many tasks from CPU. To meet users’ different speed demands of server adapters, FS has released 10G PCIe adapters and 25G/40G NIC cards. Built with the Intel controller, those PCIe adapters support multi-core processors and optimization for server and network virtualization.


The performance of the NIC card directly affects the data transfer rate of the overall network. Whether you are looking for network adapters for home uses, or a server network card for SMB or data centers, it’s necessary to understand what is a network interface card, component and function of NIC as well as types of NIC before purchasing a network interface card. To know more about how to buy a network card, you can read this post: How to Choose a Network Card?.


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