In Seven Layer of OSI
Model, Network Card falls both to Physical layer and Data Link layer
device. 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. It implements the electronic circuitry required to
communicate using a specific physical layer and data link layer
standard.
Ethernet is the most common network technology that exist. It 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.
There are four techniques used to transfer data, the network card
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.
Most computers nowadays comes with a built-in network card on their
motherboard.
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