1Lesson 2—Networking BASICS

Networking BASICSNetwork Media

Unit 1

Lesson 2

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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