Transcript Book cover slide

Section 4.1
• Identify important network connectivity devices
• Define hubs, switches, routers, and gateways
• Describe modem functionality
Section 4.2
• Differentiate between types of network cabling
• Select cabling based on network needs
Section 4.3
• Explain how a NIC functions
• Understand NIC configurations
Section 4.4
• Describe types of wireless network technologies
• Explain risks of wireless networking
pp.
4.1
Network Connectivity Devices
Guide to Reading
Main Ideas
Key Terms
Nodes, hubs, switches,
and routers are all
connective devices that
allow the transmission of
communications traffic
over networks. The traffic
moves between nodes on
the network. Modems are
devices that allow remote
nodes to access a
network.
repeater
segment
bridge
switch
router
brouter
gateway
modulation
demodulation
104-109
pp.
4.1
104-109
Network Connectivity Devices
Hubs
The hub is a central hardware component for many LANs. Hubs
operate at the Physical Layer in the OSI model. Hubs contain
multiple ports, and can connect to other hubs to expand the
network.
pp.
4.1
104-109
Network Connectivity Devices
Repeaters
Repeaters operate at the
Physical Layer of the OSI
model. Essentially,
repeaters allow smaller
LANs to grow into larger
LANs by moving
transmissions from one
network segment to
another.
repeater A device that can
be used to connect two
cables and that boosts the
signal before sending it
along. (p. 105)
segment A section of the
network that includes the
cable and nodes that are
connected to a device, such
as a repeater, hub, or bridge.
(p. 105)
pp.
4.1
104-109
Network Connectivity Devices
Bridges and Switches
Bridges can be used to
connect dissimilar network
segments that use
different methods of
transferring data.
In today’s networks, it is
uncommon to find bridges
because switches
provide “multibridge”
capability.
bridge A device used to
connect two network
segments together. (p. 105)
switch A multiport bridge
that allows several segments
of a network to communicate
with one another. (p. 106)
pp.
4.1
104-109
Network Connectivity Devices
Bridges and Switches
An important function of bridges and switches is to minimize
collision of data packets by creating collision domains. Bridges
and switches prevent the passing of collisions from one network
segment to another.
pp.
4.1
104-109
Network Connectivity Devices
Routers
Bridges are clever
devices, but they are not
as smart as routers.
Brides forward data from
one network segment to
another, routers:
• forward packets from one
network to another
• determine the best route to
use to deliver the data
router A network device
used to connect networks of
different types and that
forwards packets from one
network to another, even
those separated by great
distances. A router
determines the best route to
use to deliver the data.
(p. 107)
pp.
4.1
104-109
Network Connectivity Devices
Routers
Brouters are hybrids that
combine the capabilities
of bridges and routers.
Like bridges, they work at
the Data Link Layer to
transfer and filter network
traffic. Like routers, they
also work at the Network
Layer to route packets
from one network to
another.
brouter A network hybrid
device that combines the
capabilities of bridges and
routers. (p. 108)
pp.
4.1
104-109
Network Connectivity Devices
Gateways
Gateways enable
dissimilar networks to
communicate. Gateways
operate at higher levels in
the OSI model such as
the Application,
Presentation, and Session
layers. In some cases,
they operate at all seven
layers.
gateway A dedicated
network computer whose job
is to convert data packets
from one network protocol to
another. Enables dissimilar
networks to communicate.
(p. 109)
pp.
4.1
104-109
Network Connectivity Devices
Modems
A modem is a computerto-computer
communication device
that converts digital
signals from the computer
to analog signals for the
telephone lines. The word
“modem” comes from the
two operations it handles:
• modulation
• demodulation
modulation The process on
changing the digital signal to
an analog signal on the
sending computer. (p. 109)
demodulation The process
of converting the analog
signal back to a digital signal
on the receiving computer.
(p. 109)
pp.
4.2
111-116
Network Media
Guide to Reading
Main Ideas
Key Terms
Cable is used to connect
network devices. There
are many types of
networking cable in use
today. Different types of
cable have particular
strengths and
weaknesses, most notably
in the speed at which they
can transfer information.
shielding
noise
crosstalk
attenuation
BNC connector
twisted-pair cable
unshielded twisted-pair
(UTP)
shielded twisted-pair
(STP)
fiber optic cable
pp.
4.2
111-116
Network Media
Cables
The vast majority of networks are connected by some sort
of cabling. The cables are the network transmission media
that carry signals between computers.
Three major groups of cabling connect the majority of
networks:
• coaxial
• twisted-pair
• fiber optic
pp.
4.2
111-116
Network Media
Cables
Coaxial cable consists of
a core of copper wire
surrounded by insulation,
a braided metal
shielding, and an outer
cover.
shielding A layer of
covering that grounds a
cable and protects it from
electric noise and crosstalk.
(p. 111)
pp.
4.2
111-116
Network Media
Cables
The shielding layer grounds
the cable and protects it from
electrical noise and
crosstalk so the data are not
distorted.
noise Stray electronic
signals that interfere with
data transmissions along a
cable and slow the
transmission speed. (p. 111)
Coaxial cable is more
resistant to interference and
attenuation than twisted-pair
cabling.
crosstalk Signal overflow
from an adjacent wire that
distorts the data signal.
(p. 111)
The farther the signal travels,
the more the signal fades.
Coaxial cable is more
resistant to interference and
attenuation than twisted-pair
cabling.
attenuation The process of
data losing signal strength as
the data are transmitted
along a cable. (p. 112)
pp.
4.2
111-116
Network Media
Cables
Connection Hardware
10Base2 and 10Base5
cabling use special
connection components,
known as BNC
connectors.
BNC connector A hardware
component used to make the
connections between the
cable and the computers.
(p. 112)
pp.
4.2
Network Media
Cables
There are several
components in the BNC
family, such as:
• The BNC cable connector
• The BNC T connector
• The BNC barrel connector
• The BNC terminator
111-116
pp.
4.2
111-116
Network Media
Cables
The twisting of the
twisted-pair cable wire
cancels out crosstalk from
adjacent pairs of cable.
The higher the number of
twists per foot of cable,
the more effectively it
cancels out crosstalk.
The total number of pairs
in a cable varies,
depending on the purpose
of the cable.
twisted-pair cable A type of
cable that consists of two
insulated strands of copper
wire twisted around each
other. (p. 113)
pp.
4.2
111-116
Network Media
Cables
Two types of twisted-pair
cable are:
• unshielded twisted-pair
(UTP)
• shielded twisted-pair
(STP)
Of the two types, UTP
cable is most prevalent.
Its popularity can be
attributed to the fact that
most buildings are
prewired for telephone
service.
unshielded twisted-pair
(UTP) A type of twisted-pair
cabling that does not have
an extra shielding layer to
help eliminate noise
interference. However, it is
highly affordable. (p. 113)
shielded twisted-pair (STP)
A type of twisted-pair cabling
that uses a woven copperbraid jacket to protect the
transmitted data from outside
interference. (p. 113)
pp.
4.2
111-116
Network Media
Cables
Twisted-pair cabling uses RJ-45 connectors, which are
similar to RJ-11 telephone connectors, to connect to a
computer.
pp.
4.2
111-116
Network Media
Cables
In a fiber optic cable,
pulses of light travel down
extremely thin tubes of
glass or plastic to transmit
data.
The signal—a light
pulse—can be transmitted
over many miles very
quickly.
fiber optic cable A type of
cable made up of extremely
thin tubes of glass or plastic
that allow pulses of light to
travel through it to transmit
data. (p. 115)
pp.
4.2
111-116
Network Media
Selecting Cabling
The cabling you select depends on the needs of a
particular site. To determine which type of cable is best,
consider the following guidelines.
pp.
4.2
Network Media
You Try It
• Activity 4A – Making Your Own Network Cable (p. 114)
111-116
pp.
4.3
117-123
Network Interface Cards
Guide to Reading
Main Ideas
Key Terms
The NIC is the direct link
between the computer
and the cable. Choose
NICs carefully by
identifying the computer’s
bus architecture and the
connector type used on
the network. Specialized
NICs allow connections
through different media.
programmable read-only
memory (PROM)
boot-on-LAN
pp.
4.3
117-123
Network Interface Cards
The Role of the NIC
The NIC has four primary roles:
1. The NIC prepares data from the computer for the network
cable.
2. It sends the data to another computer.
3. It controls the flow of data between the computer and the
cabling system.
4. It receives incoming data from the cable and translates the
data into bytes that can be understood by the computer’s
central processing unit (CPU).
pp.
4.3
117-123
Network Interface Cards
The Role of the NIC
Before data are sent over the network, a conversation
between the sending and receiving NICs takes place. The
following items must be determined before any
transmission can begin:
• maximum size of the data groups to be sent
• amount of data to be sent before confirmation of receipt is given
• time intervals between sending data chunks
• amount of time to wait before confirmation is sent
• how much data each NIC can hold before it overflows
• data transmission speed
pp.
4.3
117-123
Network Interface Cards
Installation of a NIC
NICs act as the physical interface between the computer
and the network cable.
pp.
4.3
117-123
Network Interface Cards
Selecting the Right NIC
To ensure compatibility between the computer and the
network, the NIC must:
• fit with the computer’s internal structure (data bus architecture).
• contain the correct type of cable connector for the cabling.
pp.
4.3
117-123
Network Interface Cards
Selecting the Right NIC
The NIC performs three important functions to coordinate
activities between the computer and the cabling:
1. Makes the physical connection to the cable
2. Generates the electrical signals that travel over the cable
3. Controls access to the cable by following specific rules
pp.
4.3
117-123
Network Interface Cards
Specialized NICs
You may encounter some
situations that require the
use of specialized network
cards. Some examples
include:
• wireless NICs
• fiber optic NICs
• programmable read-only
memory (PROM)
• boot-on-LAN
programmable read-only
memory (PROM) A chip that
contains the hardwired code
to start the computer and
connect the user to the
network. With remote-boot
PROMs, diskless
workstations can join the
network when they start.
(p. 122)
boot-on-LAN The process
that enables the PC to boot
from a server rather than the
local hard drive. (p. 122)
pp.
4.3
Network Interface Cards
You Try It
• Activity 4B – Installing a Network Interface Card (p. 119)
117-123
pp.
4.4
125-128
Wireless Networking
Guide to Reading
Main Ideas
Key Terms
Infrared signals use light
beams to transmit from
computer to device.
Narrowband radio signals
use radio frequencies to
transmit data. Spreadspectrum radio
broadcasts data over a
range of frequencies.
Microwave technology
includes ground to
satellite transmission.
infrared
narrowband radio
spread-spectrum radio
hop
microwave
wired encryption privacy
(WEP)
pp.
4.4
125-128
Wireless Networking
Infrared Light
There are four types of
infrared networks:
• line-of-sight
• scatter infrared
• reflective
• broadband optical telepoint
infrared A type of light
beam used in wireless
networks to transmit the data
between devices. (p. 125)
pp.
4.4
125-128
Wireless Networking
Narrowband Radio
Narrowband radio is
similar to broadcasting
from a radio station. The
broadcast range is 3,000
meters (9,842 feet), and
does not require line-ofsight focusing. However,
because the signal is high
frequency, it is subject to
attenuation from steel and
load-bearing walls.
narrowband radio A highfrequency transmission
similar to broadcasting from
a radio station. The user
tunes both the transmitter
and the receiver to a certain
frequency. (p. 126)
pp.
4.4
125-128
Wireless Networking
Spread-Spectrum
Spread-spectrum radio
broadcasts signals over a
range of frequencies. This
helps it avoid narrowband
communication problems.
The available frequencies
are divided into channels,
known as hops.
spread-spectrum radio A
transmission technology that
broadcasts signals over a
range of frequencies, thus
providing security for the
transmission. (p. 126)
hop One portion of a
transmission’s journey
between two points. (p. 126)
pp.
4.4
125-128
Wireless Networking
Microwave Technology
Microwave systems can
be used for the following:
• satellite-to-ground links
• between two buildings
• across large, flat, and open
areas, such as bodies of
water or deserts
microwave Part of the
electromagnetic spectrum,
and a form of radiation that
can be used for short- and
long-distance
communications systems.
(p. 127)
pp.
4.4
125-128
Wireless Networking
Microwave Technology
A microwave system can be used to transmit data from
building to building.
pp.
4.4
125-128
Wireless Networking
Security Risks
Wireless technology is
somewhat more prone to
security risks. Due to the
fact that the signal is
broadcast in a certain
radius, anyone within that
radius can potentially
intercept that signal.
Most wireless NICs and
access points have a
built-in security feature,
called wired encryption
privacy (WEP).
wired encryption privacy
(WEP) A security feature
that, when activated,
encrypts the data prior to
transmission by the NIC. At
the receiving end, the data
are decrypted. Most wireless
NICs and access points have
this security feature built in.
(p. 128)
Chapter 4
Resources
For more resources on this chapter, go to the Introduction
to Networks and Networking Web site at
http://networking.glencoe.com.