Transcript A Big Test Result - Knowledge Systems Institute

Introduction to
Computer Networks
The Network Interface Card
Network interface cards (NICs) provide the
interface between cables and computers. This
lesson explores the many different types of
cards and how their performance affects a
network.
The Role of the NIC
• NICs, act as the physical interface or connection
between the computer and the network cable.
• The NIC contains the hardware and firmware
(software routines stored in read-only memory,
ROM) programming that implements the Logical
Link Control and Media Access Control functions.
The Role of the NIC
• Prepare data from the computer for the
network cable.
• Send the data to another computer.
• Control the flow of data between the computer
and the cabling system.
• Receive incoming data from the cable and
translate it into bytes that can be understood by
the computer's central processing unit (CPU).
Network Address (MAC Address)
• NIC also has to advertise its own location, or
address, to the rest of the network to distinguish it
from all the other cards on the network.
• A committee of the Institute of Electrical and
Electronics Engineers (IEEE) assigns blocks of
addresses to each NIC manufacturer. The
manufacturers hardwire these addresses into chips
on the card by a process known as "burning" the
address into the card.
• Each NIC— and therefore each computer — has an
unique address (MAC address) on a network.
Configuration Options and Settings
• Network interface cards often have configurable options
that must be set in order for the card to function properly.
• The following are examples of configurable options:
• Interrupt (IRQ)
• Base input/output (I/O) port address
• Base memory address
• Transceiver
Configuration Options and Settings
• Network interface cards often have configurable options
that must be set in order for the card to function properly.
• The following are examples of configurable options:
• Interrupt (IRQ)
• Base input/output
(I/O) port address
• Base memory address
• Transceiver
Selecting the Transceiver
• 2(9)
3
4
5
6
7
8
10
11
12
13
14
15
EGA/VGA Adapter
Available (Serial port [COM2, COM4] or bus mouse)
COM1, COM3
Available (parallel port [LPT2] or sound card)
Floppy-disk controller
Parallel port (LPT1)
Real-time clock
Available
Available
Mouse (PS/2)
Math coprocessor
Hard-disk controller
Available (secondary hard-disk controller)
NIC, Bus, and Cable Compatibility
• To ensure compatibility between the computer and
the network, the NIC must:
• Fit with the computer's internal structure (data bus
architecture).
• Have the right type of cable connector for the cabling.
• Data Bus Architecture:
• Industry Standard Architecture (ISA)
• Extended Industry Standard Architecture (EISA)
• Micro Channel Architecture
• Peripheral Component Interconnect (PCI)
NIC, Bus, and Cable Compatibility
Network Cabling and Connectors
• To select the appropriate NIC for your network, you
first need to determine the type of cabling and
cabling connectors it will have.
• Some NICs have more than one interface connector.
Network Performance (1)
• You can speed up the movement of data through the
card by adding the following enhancements:
• Direct memory access (DMA): With this method, the
computer moves data directly from the NIC's buffer to
the computer's memory, without using the computer's
microprocessor.
• Shared adapter memory: In this method, the NIC
contains RAM that it shares with the computer. The
computer
identifies this RAM as if it is actually installed
in the computer.
• Shared system memory: In this system, the NIC's
processor selects a section of the computer's memory an
Network Performance (2)
• Bus mastering: the NIC takes temporary control of
the computer's bus, bypasses the computer's CPU,
and moves data directly to the computer's system
memory. This speeds up operations by freeing the
computer's processor to deal with other tasks. Bus
mastering can improve network performance by 20
to 70 percent.
• RAM buffering: Network traffic often travels too fast for
most NICs to handle. RAM chips on the NIC serve as a
buffer. When the card receives more data than it can
process immediately, the RAM buffer holds some of the
data until the NIC can process it. This speeds up the
card's performance and helps keep the card from
becoming a bottleneck.
Network Performance (3)
• On-board microprocessor With a microprocessor, the
NIC does not need the computer to help process
data. Most cards feature their own processors that
speed network operations.
Specialized NICs
• Wireless NICs: These NICs can be used to create an allwireless LAN or to add wireless stations to a cabled
LAN.
• Usually, these NICs are used to communicate with a
component called a wireless concentrator that acts as a
transceiver to send and receive signals.
• Fiber-Optic NICs: fiber-optic network cards allow direct
connections to high-speed fiber-optic networks.
• Remote-Boot PROMs: With remote-boot PROMs, diskless
workstations can join the network when they start.