Transcript IT113 Structured Cabling

Unit 3
Key Concept 1: Cable Types
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Type of Data Cables
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Unshielded Twisted-Pair (UTP)
Shielded Twisted-Pair (STP)
Screened Twisted-Pair (SCTP)
Coaxial Cable (COAX)
Fiber-Optic Cable (FO)
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UTP
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Four Pairs of Copper Cable
Number of twists varies per inch
No shielding
Very easy to work with
Most common cable for LAN
Cat 3, Cat 5, Cat 5e, Cat 6, Cat 7
will be defined in standards later
in the course
◦ Most susceptible to
Electromagnetic Interference
(EMI)
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STP
o
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Similar to UTP
Pairs shielded
Core shielded
SCTP
o
o
Hybrid of STP
and UTP
Foil shield or screen
Both the cables must be
grounded end to end with no
gaps in shield coverage.
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Coax
◦ Single conducting core
◦ Core shield
◦ Mesh shield
◦ 50 Ohm RG-58 (thinnet) is for outdated 10Base-2
Ethernet
◦ 75 Ohm RG-6U commonly used for highdefinition television (HDTV) and broadband data
applications
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FO
◦ Central glass core
◦ Cladding prevents light loss
◦ Dielectric strengthening material
protects core
◦ Single strand, dual strand
(pictured), and multistrand cables
are common
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Single-Mode FO
◦ Single beam
◦ Smaller core
◦ Usually WAN
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Multimode FO
◦ Multiple beams
◦ Larger core
◦ Usually LAN
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Usage
◦ General Purpose
◦ Plenum
◦ Riser
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UTP
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Twists per inch
Gauge (thickness)
Length
Solid/Stranded
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Unit 3
Key Concept 3: Network Topologies
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Topology refers to the physical layout of the
elements of the cabling system structure
It affects the type of networking equipment,
cabling, growth path, and network
management
In this unit, you will focus on physical
topology, but modern networks often have
logical topologies that differ from the
physical connections.
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Bus
◦ Single cable connects all machines
◦ Each machine links to the cable using a Tconnector
◦ Each end of the cable requires a terminator
(resistor)
◦ A break in the cable results in total
communication failure
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Ring
◦ Single cable connects all machines
◦ Each machine links to the cable using
a T-connector
◦ Each end of the cable connect
together
◦ A break in the cable results in total
communication failure
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Star
◦ Single cable connects each machine to central device
◦ A break in the cable results in communication failure at only one host
◦ All connections configured at a central location making
reconfiguration and troubleshooting simpler
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Full Mesh
◦ Every machine links to
every machine
◦ Impractical due to number
of connections
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Partial Mesh
Full Mesh
◦ Hosts have 2 or more
redundant links
◦ Often used in WAN to
provide redundant
connections between
routers
Partial Mesh
http://www.cisco.com/en/US/i/Other/cpress_ill/NDCS-JULY1998/nd200901.jpg
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How do we control the flow of traffic on a
network?
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Token Ring
FDDI
Ethernet
ATM and SONET
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Token Ring
◦ A small packet (token) is
generated and passed to each host
in order
◦ A host may only transmit once
each time it is in possession of the
token
◦ Although the token passes in a
logical ring from host to host, the
system is often implemented in a
physical star topology where the
central hub, or Media Attachment
Unit (MAU) generates the token
◦ Defined by IEEE 802.5 (and
revisions) up to 16Mbps
LOGICAL
PHYSICAL
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Fiber Data Distributed
Interface (FDDI)
◦ Uses dual, counter rotating
tokens
◦ Possession of token grants
unlimited transmission for
a specific time period
◦ Speeds reach up to 125
Mbps using fiber-optic
media
◦ Defined by ANSI X3T9.5
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Unit 3
Key Concept 4: Bandwidth, Frequency and Data Rate
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Frequency
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Number of sinusoidal cycles completed over time
1 cycle per second = 1 Hertz (Hz)
1,000,000 cycles per second = 1 Megahertz (MHz)
Higher frequency means more noise (distortion)
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Bandwidth
◦ Maximum frequency at which data can be transmitted and
received effectively
◦ A function of distance, frequency, and signal to noise ration
(SNR)
◦ Common measure for copper
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Data Rate
◦ The number of bits per
second that are
transmitted on a cable
◦ Common measure for
copper and fiber
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A ratio of output power to input power
Represents signal (power) loss or gain
Higher decibel means higher loss/gain
http://rfidsoup.pbworks.com/f/Decibel_Function.jpg
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Now check out the animations from chapter 1,
Introduction to Data Cabling.
Refer to the Instructor’s Resource Section
in the Instructor Guide for Directions on
Downloading the Animations
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Main link to the Animations:
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http://bcs.wiley.com/he-bcs/Books?action=index&itemId=0470477075&bcsId=5638
Note: You must have an active Internet connection
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Attenuation
◦ Natural loss of signal over distance
◦ Example: Hard to hear someone farther away
◦ Measured in db
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Attenuation sources
◦ Conductor Resistance
◦ Mutual Capacitance
◦ Impedance
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Noise
◦ Anything electrical on the cable that is not part of the original
transmission
◦ Motors, AC electrical cables, and adjacent cables all cause
noise.
http://www.ecmweb.com/images/archive/304ecm39fig1.jpg
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When a signal “jumps” from one wire to another
May be Near-End or Far-End Crosstalk
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Electricity travel at a constant rate
UTP has twists and so the distance travelled varies
slightly between pairs
The delay between signal arrival on different pairs
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

Now check out the animations from
chapter 1, Introduction to Data Cabling.
Refer to the Instructor’s Resource Section
in the Instructor Guide for Directions on
Downloading the Animations

Main link to the Animations:

http://bcs.wiley.com/he-bcs/Books?action=index&itemId=0470477075&bcsId=5638
Note: You must have an active Internet connection
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