NIC (network interface card):-
NIC (network interface card) is a gadget that works as a
bridge between computers. In other words, this piece of equipment is used to
join together multiple computer systems in a local area network (LAN). Though,
networked computers are required protocols and agreed-upon communication
languages in order to correspond with each other and for transmitting data
packets on these machines. That means network interface card is very important
to link the computers so data can be sent and received on them within a LAN. So
while constructing a LAN, NIC must be fitted into each communicating computer
within that network. Moreover, all installed NICs in this network must have the
same designs and architectures. Ethernet cards and Token Ring cards are the
best examples of these technologies.
A
network interface card (Ethernet card)
will be installed in the computer’s slot. each Ethernet network controller is
having a unique address of 48 bits serial numbers which is known as MAC (media
access control) address. Like a home address, MAC addresses are used to move
ahead traffic to a computer over a network. But these addresses are stored up
in the computer’s ROM (read only memory).
The
network interface card allows the computers of a network to communicate as OSI
layer 1 and layer 2 hardware devices. It also makes possible the physical
contact with a network’s resource or other medium. With NIC a low-level
addressing structure with the use of MAC addresses becomes possible. It as well
permits the computers users to establish a connection with each other by using
cables or else to communicate wirelessly.
Hubs
or switches are used to pass data and information between a network’s computers
with the help of MAC addresses. So whenever we will go to buy the LAN components, make sure
first that the NICs have the similar capabilities as a hub or a switch of that
network has. So NIC for a wireless network can’t chatter with a wired hub or
switch and vice versa. Anyhow, for the greater speed and best performance of
the network, try to use the newer versions of hardware.
Following are the 4 possible techniques that can be used by
NIC to transfer the data:
- Polling
- Programmed Input/output (I/O)
- Interruption driven I/O
- Direct memory access
Use of I/O device:
- Transferring packet between network and memory
- Controlled by CPU
Send packet to network using NIC
- CPU assembling a packet in memory
- CPU transferring the packet to NIC
- NIC Transmitting the packet to network
Receive packet from network using NIC
- CPU informed NIC the storage location for coming packet
- NIC waiting for packet from network
- NIC placing packet into specified location
- NIC informing CPU
Inefficiencies
Ethernet shared medium =>
- NIC receiving a lot of packets that intended for other stations
- NIC wasting CPU for wrong interruption and forwarding wrong packet
Network traffic burst =>
- Packet loss if NIC can’t forward packets
Packet size bigger than the bus width =>
- Multiple transfer required for one packet
- Multiple CPU interrupt
Bus interconnect shared medium =>
- NIC waiting for transfer turn to access memory
Solution:
- Avoid using CPU whenever possible
- Improve NIC own processing, storage and communication ability
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