Networking BASICS
Network Media
Unit 1
Lesson 2
Lesson 2—Networking BASICS
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Objectives
• Explain how data transmissions are
sent and received.
• List and describe the types of
transmission media.
• Describe the functions of a network
interface card.
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Types of Networks
• There are two types of
networks by which
information is transmitted:
– circuit switched networks
– packet switched networks
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Circuit Switched Network
• There is a dedicated and direct physical
connection between sender and receiver.
• No other transmissions can take place while
the connection is active.
• Once the transmission is ended, other
connections can be made with other devices.
• It is ideal for voice communications because
there are no interruptions from other devices
or delays.
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Packet Switched Network
• This network requires data transmission be broken
into smaller units called packets.
• Each packet is sent independently through the
network.
• It is used for data transmission because data is not
as time-sensitive as voice communication.
• It allows multiple devices to share one line or
frequency.
• It facilitates error correction.
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Signaling Techniques
• There are two ways that a signal is
sent across a network medium:
– baseband signaling
– broadband signaling
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Baseband Signaling
• Sends one data signal across the network
media
• Entire capacity of the media is used for the
one data signal
• Signals are transmitted in a digital format
• Many devices can send and receive across
the medium, but only one at a time
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Baseband Signaling
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Broadband Signaling
• Divides the cable into several different
channels
• Signals are transmitted at different
frequencies in an analog mode
• Allows many different signals to be sent
simultaneously on a single cable
• Signal sent in only one direction
• Used for computer network data
transmissions
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Broadband Signaling
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Factors Affecting Transmissions
• The flow of a signal down the network
media can become distorted.
• Common types of distortions are
attenuation and interference.
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Attenuation
• Loss of signal power
• Measured by the decrease
in decibels (db) over a
specific distance
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Interference
• Interference is caused when a strong external signal
interferes with a signal.
• Radio frequency interference (RFI) - interference
caused by broadcast signals from a radio or
television transmitter.
• Electromagnetic interference (EMI) - motor or
source of intense electrical activity creates an
electromagnetic signal that interferes with a data
signal.
• Near end crosstalk (NEXT) and Far end crosstalk
(FEXT) - interference from another data signal being
transmitted on adjacent wire.
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Transmission Media
• Copper cables
• Fiber optic cables
• Wireless
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Copper Cables
•
•
•
•
Thin coaxial
Shielded twisted pair (STP)
Unshielded twisted pair (UTP)
UTP rated by Category 1 - 6
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Copper Cables
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Copper Cables
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Fiber Optic
• This cable uses a thin cylinder of glass to
send light impulses.
• The cable consists of a strand of glass (core)
surrounded by a glass tube (cladding).
• Single mode - one light source flashes a light
down the cable.
• Multimode - supports many simultaneous
light transmissions.
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Fiber Optic
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Wireless
• Transmission is sent and received through
invisible waves
• Less expensive than copper or fiber optic
lines.
• Allows the user to move freely around the
office or campus and still remain connected to
the network
• Fastest-growing segment of network media
today
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Wireless Transmissions
• Infrared transmits data using infrared (IR)
light.
• IR shares many of the same properties as
visible light .
• Radio frequency signals can be transmitted
over radio waves similar to local radio station
transmissions.
• The signal comes in at a lower power level
and does not reach as far.
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Network Interface Card
• The NIC serves as the connection between
the personal computer and the network
media.
• It connects to the computer on its base by
plugging into an expansion slot of the
computer.
• Another connection is accessible from the
outside of the computer and has connections
for the cables to plug into the network.
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Network Interface Card
• Changes from parallel to serial
transmission
• Creates packets
• Determines when to send
• Transmits packet
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Network Interface Card
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Summary
• Switching involves moving (switching) the signal from one wire
or frequency to another. A circuit switched network creates a
dedicated and direct physical connection between the sender
and receiver. No other transmissions can take place while the
connection is active, but once the transmission is ended, other
connections can be made with other devices. Circuit switching is
ideal for voice communications. Computer networks sending
data use packet switched networks. Packet switching requires
that the data transmission be broken into smaller units called
packets. Each packet is then sent independently through the
network to reach the destination.
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Summary (continued)
• Baseband signaling sends one data signal across the network
media. The entire capacity of the media is used for the one data
signal that is transmitted in a digital format, which is made up of
short impulses of off and on. The other type of signaling technique is known as broadband signaling. Broadband transmission divides the cable into several different channels. It does this
because the signals are transmitted at different frequencies in
an analog, or continuous, mode. Broadband transmission allows
many different signals to be sent simultaneously on a single
cable. Computer data networks use baseband signaling instead
of broadband signaling.
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Summary (continued)
• The flow of a signal down the network media can sometimes
become distorted. The two common types of distortions are
attenuation and interference. As the data travels, it meets resistance, which causes the signal to weaken gradually. This loss of
signal power is known as attenuation. Interference or noise is
caused when a strong external signal interferes with the signal
being transmitted. Radio frequency interference (RFI) refers to
interference caused by broadcast signals from a radio or
television transmitter. Electromagnetic interference (EMI) may
be caused by a variety of sources. The source of near end
crosstalk (NEXT) interference is from another data signal being
transmitted. Far end crosstalk (FEXT) is similar to NEXT except
that the interference is measured at the far end of the wire.
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Summary (continued)
• There are many different types of network media, yet they all
can be classified into three major categories: copper, fiber optic,
and wireless. Thin coaxial cable is approximately one-quarter of
an inch in diameter, has a single copper wire at its center, and is
surrounded by a layer of insulation. Around the insulation is a
braided copper mesh channel, and everything is covered by a
thick outer shield of insulation. Twisted pair cable has become
the standard today for copper cabling used in computer networks, replacing thin coaxial cable. Twisted pair cable is two
insulated copper wires that are twisted around each other. Each
pair is then bundled together with other pairs in a jacket. There
are two types of twisted pair cables. Shielded twisted pair (STP)
cables have a foil shielding on the inside of the jacket, which
reduces interference. Unshielded twisted pair (UTP) cables do
not have any shielding.
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Summary (continued)
• A fiber optic cable uses a very thin cylinder of glass, instead of
copper, at its center. Fiber optic cables send light impulses
instead of transmitting electrical signals. Wireless communication uses no visible connection, such as a copper cable or fiber
optic line, between the network devices. Instead, the transmission is sent and received through invisible waves. Transmission
signals can be sent by infrared light waves or radio frequency
waves.
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Summary (continued)
• When connecting a personal computer to the transmission
media on a LAN, hardware known as a network interface card
(NIC) is used. A NIC serves as the connection between the
personal computer and the network media. The NIC connects to
the computer on its base by plugging into one of the expansion
slots of the computer. The other connection, found on the side of
the NIC, is accessible from the outside of the computer and has
connections for the cables to plug into the network (or an
antenna for wireless transmissions). These connections depend
on the type of network media being used.
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