LAN card

A network card, network adapter or NIC (network interface card) is a piece of computer

hardware designed to allow computers to communicate over a computer network. It is both an

OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides physical access

to a networking medium and provides a low-level addressing system through the use of MAC

addresses. It allows users to connect to each other either by using cables or wirelessly.

Although other network technologies exist, Ethernet has achieved near-ubiquity since the mid-

1990s. Every Ethernet network card has a unique 48-bit serial number called a MAC address,

which is stored in ROM carried on the card. Every computer on an Ethernet network must have

a card with a unique MAC address. No two cards ever manufactured share the same address.

This is accomplished by the Institute of Electrical and Electronics Engineers (IEEE), which is

responsible for assigning unique MAC addresses to the vendors of network interface controllers.

Whereas network cards used to be expansion cards 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. These motherboards either have Ethernet capabilities

integrated into the motherboard chipset, or implemented via a low cost dedicated Ethernet

chip, connected through the PCI (or the newer PCI express 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 and data link layer standard such as Ethernet or token ring. This provides a base for a full

network protocol stack, allowing communication among small groups of computers on the same

LAN and large-scale network communications through routable protocols, such as IP.

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

• Polling is where the microprocessor examines the status of the peripheral under program

control.

• Programmed I/O is where the microprocessor alerts the designated peripheral by

applying its address to the system's address bus.

• Interrupt-driven I/O is where the peripheral alerts the microprocessor that it's ready to

transfer data.

• DMA is where the intelligent peripheral 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, BNC, or AUI socket where the network cable is

connected, and a few LEDs to inform the user of whether the network is active, and whether or

not there is data being transmitted on it. The Network Cards are typically available in 10/100/

1000 Mbit/s(Mbit/s). This means they can support a transfer rate of 10 or 100 or 1000 Megabits

per second.

Notable manufacturers

• 3Com

• AMD

• AEI Intelligent Technologies

• ASIX Electronics

• Belkin

• Broadcom

• Cisco

• Digital Equipment Corporation (DEC)

• Intel

• Marvell Technology Group

• National Semiconductor

• Netgear

• Novell

• Realtek

• VIA Networking

A 1990s Ethernet network interface controller card which connects to the motherboard via the now-
obsolete ISA bus.

Speeds:

• 10 Mbit/s

• 100 Mbit/s

• 1000 Mbit/s up to 160 Gbit/s






USB Lan Card, Supports 10Mbps and 100Mbps N-way Auto Negotiation

Operation

Model Number:WS-U20LAN

Key Specifications/Special Features:

• Integrated fast Ethernet MAC, physical chip and transceiver in one chip

• Supports 10Mbps and 100Mbps N-way auto negotiation operation

• Compliance with USB interface version 1.0/1.1/2.0

• Full-speed (12Mbps) USB device