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A network card, network adapter, network interface controller (NIC), network interface card, or LAN adapter is a computer hardware
Computer hardware

A personal computer is made up of computer hardware, multiple physical components onto which can be loaded into a multitude of software that perform the functions of the computer....
 component designed to allow computers to communicate over a computer network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
. It is both an OSI layer
OSI model

The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection initiative....
 1 (physical layer
Physical layer

The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking.The Physical Layer comprises the basic hardware transmission technologies of a network....
) and layer 2 (data link layer
Data link layer

The Data Link Layer is layer 2 of the seven-layer OSI model of computer networking.The Data Link Layer is the protocol layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network network segment....
) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
es. It allows users to connect to each other either by using cables or wirelessly.

Although other network technologies exist, Ethernet
Ethernet

Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether....
 has achieved near-ubiquity since the mid-1990s.






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A network card, network adapter, network interface controller (NIC), network interface card, or LAN adapter is a computer hardware
Computer hardware

A personal computer is made up of computer hardware, multiple physical components onto which can be loaded into a multitude of software that perform the functions of the computer....
 component designed to allow computers to communicate over a computer network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
. It is both an OSI layer
OSI model

The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection initiative....
 1 (physical layer
Physical layer

The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking.The Physical Layer comprises the basic hardware transmission technologies of a network....
) and layer 2 (data link layer
Data link layer

The Data Link Layer is layer 2 of the seven-layer OSI model of computer networking.The Data Link Layer is the protocol layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network network segment....
) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
es. It allows users to connect to each other either by using cables or wirelessly.

Although other network technologies exist, Ethernet
Ethernet

Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether....
 has achieved near-ubiquity since the mid-1990s. Every Ethernet network card has a unique 48-bit serial number called a MAC address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
, which is stored in ROM
Read-only memory

Read-only memory is a class of computer storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified , it is mainly used to distribute firmware ....
 carried on the card. Every computer on an Ethernet network must have a card with a unique MAC address. Normally it is safe to assume that no two network cards will share the same address, because card vendors purchase blocks of addresses from the Institute of Electrical and Electronics Engineers
Institute of Electrical and Electronics Engineers

The Institute of Electrical and Electronics Engineers or IEEE is an international non-profit, professional body for the advancement of technology related to electricity....
 (IEEE) and assign a unique address to each card at the time of manufacture.

Whereas network cards used to be expansion card
Expansion card

An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard to add additional functionality to a computer system....
s that plug into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
. These either have Ethernet capabilities integrated into the motherboard chipset or implemented via a low cost dedicated Ethernet chip, connected through the PCI
Peripheral Component Interconnect

The PCI Local Bus , or Conventional PCI, is a computer bus for attaching computer hardware in a computer. These devices can take either the form of an integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification or an expansion card that fits into a socket....
 (or the newer PCI express
PCI Express

Peripheral Component Interconnect Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI Local Bus, PCI-X, and Accelerated Graphics Port standards....
 bus). A separate network card is not required unless multiple interfaces are needed or some other type of network is used. Newer motherboards may even have dual network (Ethernet) interfaces built-in.

The card implements the electronic circuitry required to communicate using a specific physical layer
Physical layer

The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking.The Physical Layer comprises the basic hardware transmission technologies of a network....
 and data link layer
Data link layer

The Data Link Layer is layer 2 of the seven-layer OSI model of computer networking.The Data Link Layer is the protocol layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network network segment....
 standard such as Ethernet
Ethernet

Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether....
 or token ring. This provides a base for a full network protocol stack
Protocol stack

A protocol stack is a particular software implementation of a computer networking protocol suite. The terms are often used interchangeably....
, allowing communication among small groups of computers on the same LAN
Lan

Lan , in Polish language means "field," and is a unit of land measurement used in Poland. Since the 13th century, its value has varied from one location to another....
 and large-scale network communications through routable protocols, such as IP
Internet protocol

Internet protocol may refer to:*The Internet Protocol, a specific protocol implementation in the Internet protocol suite*The Internet protocol suite, a set of communications protocols that are used for the Internet...
.

There are four techniques used to transfer data, the NIC may use one or more of these techniques.

  • Polling is where the microprocessor
    Microprocessor

    A microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit . The first microprocessors emerged in the early 1970s and were used for electronic calculators, using Binary-coded decimal arithmetic on 4-bit Word ....
     examines the status of the peripheral
    Peripheral

    A peripheral is a device attached to a host computer behind the chipset whose primary functionality is dependent upon the host, and can therefore be considered as expanding the hosts capabilities, while not forming part of the system's core computer architecture....
     under program control.
  • Programmed I/O
    I/O

    I/O may refer to:* Input/output, a system of communication for information processing systems* The input-output model, an economic model of flow prediction between sectors...
     is where the microprocessor
    Microprocessor

    A microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit . The first microprocessors emerged in the early 1970s and were used for electronic calculators, using Binary-coded decimal arithmetic on 4-bit Word ....
     alerts the designated peripheral
    Peripheral

    A peripheral is a device attached to a host computer behind the chipset whose primary functionality is dependent upon the host, and can therefore be considered as expanding the hosts capabilities, while not forming part of the system's core computer architecture....
     by applying its address to the system's address bus
    Address bus

    An address bus is a computer bus that is used to specify a memory address. When a central processing unit or direct memory access-enabled device needs to read or write to a memory location, it specifies that memory location on the address bus ....
    .
  • Interrupt-driven I/O
    I/O

    I/O may refer to:* Input/output, a system of communication for information processing systems* The input-output model, an economic model of flow prediction between sectors...
     is where the peripheral
    Peripheral

    A peripheral is a device attached to a host computer behind the chipset whose primary functionality is dependent upon the host, and can therefore be considered as expanding the hosts capabilities, while not forming part of the system's core computer architecture....
     alerts the microprocessor
    Microprocessor

    A microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit . The first microprocessors emerged in the early 1970s and were used for electronic calculators, using Binary-coded decimal arithmetic on 4-bit Word ....
     that it's ready to transfer data.
  • DMA is where the intelligent peripheral
    Peripheral

    A peripheral is a device attached to a host computer behind the chipset whose primary functionality is dependent upon the host, and can therefore be considered as expanding the hosts capabilities, while not forming part of the system's core computer architecture....
     assumes control of the system bus to access memory directly. This removes load from the CPU but requires a separate processor on the card.


A network card typically has a twisted pair
Twisted pair

Twisted pair cabling is a form of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs....
, BNC
BNC connector

File:Female BNC Connector.jpgThe BNC connector is a very common type of RF connector used for terminating coaxial cable....
, or AUI
Attachment Unit Interface

An Attachment Unit Interface is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit , sometimes known as a transceiver....
  socket where the network cable is connected, and a few LED
Light-emitting diode

A light-emitting diode , is an electronic light source. The LED was discovered in the early 20th century, and introduced as a practical electronic component in 1962....
s to inform the user of whether the network is active, and whether or not there is data being transmitted on it. Network Cards are typically available in 10/100/1000 Mbit/s varieties. This means they can support a transfer rate of 10, 100 or 1000 Megabits per second.

A Network Interface Controller (NIC) is a hardware
Computer hardware

A personal computer is made up of computer hardware, multiple physical components onto which can be loaded into a multitude of software that perform the functions of the computer....
 interface that handles and allows a network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
 capable device access to a computer network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
 such as the internet
Internet

The Internet is a global network of interconnected computers, enabling users to share information along multiple channels. Typically, a computer that connects to the Internet can access information from a vast array of available server and other computers by moving information from them to the computer's local memory....
. The NIC has a ROM
Read-only memory

Read-only memory is a class of computer storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified , it is mainly used to distribute firmware ....
 chip that has a unique Media Access Control (MAC) Address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
 burned into it. The MAC address identifies the vendor MAC address which identifies it on the LAN. The NIC exists on both the ' Physical Layer' (Layer 1) and the 'Data Link Layer' (Layer 2) of the OSI model
OSI model

The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection initiative....
.

Sometimes the words 'controller' and 'card' are used interchangeably when talking about networking
Computer networking

Computer networking is the engineering discipline concerned with communication between computer systems or Peripheral devices. Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called Request for Commentss....
 because the most common NIC is the Network Interface Card. Although 'card' is more commonly used, it is less encompassing. The 'controller' may take the form of a network card that is installed inside a computer
Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
, or it may refer to an embedded component as part of a computer motherboard
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
, a router
Router

A router is a Computer network device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers....
, expansion card
Expansion card

An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard to add additional functionality to a computer system....
, printer
Computer printer

File:Lexmark X5100 Series.jpgIn computing, a printer is a peripheral which produces a hard copy of documents stored in computer file form, usually on physical print media such as paper or Transparency ....
 interface, or a USB device.

A MAC Address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
 is a 48 bit network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
  hardware
Computer hardware

A personal computer is made up of computer hardware, multiple physical components onto which can be loaded into a multitude of software that perform the functions of the computer....
 identifier that is burned into a ROM
Read-only memory

Read-only memory is a class of computer storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified , it is mainly used to distribute firmware ....
 chip
Integrated circuit

In electronics, an integrated circuit is a miniaturized electronic circuit that has been manufactured in the surface of a thin Wafer of semiconductor material....
 on the NIC to identify that device on the network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
. The first 24 bits is called the Organizationally Unique Identifier
Organizationally Unique Identifier

An Organizationally Unique Identifier is a 24-bit number that is purchased from the Institute of Electrical and Electronics Engineers IEEE registration authority....
 (OUI) and is largely manufacturer dependent. Each OUI allows for 16,777,216 Unique NIC Addresses.

Smaller manufacturers that do not have a need for over 4096 unique NIC addresses may opt to purchase an Individual Address Block (IAB) instead. An IAB consists of the 24 bit OUI
Organizationally Unique Identifier

An Organizationally Unique Identifier is a 24-bit number that is purchased from the Institute of Electrical and Electronics Engineers IEEE registration authority....
, plus a 12 bit extension (taken from the 'potential' NIC portion of the MAC address
MAC address

In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
)

See also

  • MAC address
    MAC address

    In computer networking, a Media Access Control address , Ethernet Hardware Address , hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification....
  • TCP Offload Engine
    TCP Offload Engine

    TCP Offload Engine or TOE is a technology used in network interface cards to offload processing of the entire TCP/IP stack to the network controller....
     (TOE)
  • Host bus adapter (HBA)
  • Wireless network interface card
    Wireless network interface card

    A wireless network interface controller is a network card which connects to a radio-based computer network, unlike a regular network interface controller which connects to a wire-based network such as token ring or ethernet....
     (WNIC)
  • Ethernet
    Ethernet

    Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether....
  • Gigabit Ethernet
    Gigabit Ethernet

    Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a Data rate units#gigabit_per_second, as defined by the IEEE 802.3-2005 standard....
  • Router
    Router

    A router is a Computer network device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers....
  • IPMP
    IPMP

    IPMP, or IP network multipathing, is a facility provided by Solaris to provide fault-tolerance and load spreading for network interface cards ....