Network interface controller

From Saferpedia

Network card with BNC connector

A network interface controlle or a network adapter or a network card is a hardware component designed to allow computers to communicate with each other using a computer network. The network card has a ROM chip with a unique number called MAC (Media Access Control) address.

Purpose

Madge network card

A network card's purpose is to connect computers into a network in order to communicate with each other. It's a device of both level 1 and 2 in OSI because it offers physical access to a network environment and offers a low addressing level using the MAC address.

Although there are other network technologies, for example Token Ring, Ethernet is omnipresent on the market.

Implementation

Ethernet network card

The network card implements the necessary electronic circuit to communicate using a physical layer and a data link layer like Ethernet and Token Ring. There are four techniques used to transfer data. The network card can use one or more of these techniques.

Polling - when the microprocessor analyzes the state of the peripheral under the control of the program.
Programmed I / O (input / output) - when the microprocessor alerts the designated peripheral by applying it's address to the system's address bus.
Interrupt-driven I / O - when the peripheral alerts the microprocessor that it's ready to transfer data.
DMA - when an intelligent peripheral takes over the system's bus to access the memory direct.

Normally a network card has a connector RJ-45, BNC or AUI where the network cable is inserted. It also have two LEDs to inform the user when the network is active and if there are sent data or not. Network adapters are available in variants of 10/100/1000 Megabits per second.

A MAC address is a hardware network identifier of 48 bits written in a ROM chip on the network card and is used to identify itself on the network. The first 24 bits are called Organizationally Unique Identifier (OUI) and they are specific to the producer. Each OUI allows 16.777.216 unique addresses.