Network+ Guide to Networks, Fourth Edition

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Transcript Network+ Guide to Networks, Fourth Edition

CIS 1140 Network Fundamentals
Chapter 3 Transmission Basics and
Networking Media
Collected and Compiled
By JD Willard
MCSE, MCSA, Network+,
Microsoft IT Academy Administrator
Computer Information Systems Instructor
Albany Technical College
Attention: Accessing Demos
• This course presents many demos.
• The Demos require that you be logged in to the Virtual
Technical College web site when you click on them to
run.
• To access and log in to the Virtual Technical College
web site:
– To access the site type www.vtc.com in the url window
– Log in using the username: CIS 1140 or ATCStudent1
– *Enter the password: student
• If you should click on the demo link and you get an
Access Denied it is because you have not logged in to
vtc.com or you need to log out and log back in.
*Remember that passwords are case sensitive so enter it in all
lower case letters.
Objectives
• Explain basic data transmission concepts,
including full duplexing, attenuation, and noise
• Describe the physical characteristics of coaxial
cable, STP, UTP, and fiber-optic media
• Compare the benefits and limitations of different
networking media
• Explain the principles behind and uses for serial
connector cables
• Identify wiring standards and the best practices
for cabling buildings and work areas
Transmission Basics
• In data networking, transmit means to
issue signals to the network medium
• Transmission refers to either the process
of transmitting or the progress of signals
after they have been transmitted
Network Cabling and Communication Overview
Cabling Demo
Analog and Digital Signals
• Information transmitted via analog or digital signals
– Signal strength proportional to voltage
• In analog signals, voltage varies continuously and appears as a
wavy line when graphed over time
– Wave’s amplitude (the height of the wave) is a measure of its
strength
– Frequency: number of times wave’s amplitude cycles from
starting point, through highest amplitude and lowest amplitude,
back to starting point over a fixed period of time
• Measured in Hz
– Wavelength: distance between corresponding points on a
wave’s cycle
– Phase: progress of a wave over time in relationship to a fixed
point
• Analog transmission susceptible to transmission flaws such as noise
Analog and Digital Signals
• Digital signals composed of pulses of precise, positive voltages and
zero voltages
– Positive voltage represents 1
– Zero voltage represents 0
• Binary system: uses 1s and 0s to represent information
– Easy to convert between binary and decimal
• Bit: a single binary signal
• Byte: 8 bits
– Typically represents one piece of information
• Overhead: describes non-data information that must accompany
data for a signal to be properly routed and interpreted
Transmission Direction:
Simplex, Half-Duplex, and Duplex
• Simplex transmission: signals may travel in
only one direction (TV or Radio)
• Half-duplex transmission: signals may travel in
both directions over a medium
– Only one direction at a time (Walkie Talkies
or Intercom System)
• Full-duplex or duplex: signals free to travel in
both directions over a medium simultaneously
(Telephone)
– Used on data networks
– Channel: distinct communication path
between nodes
• May be separated logically or physically
Full Duplex vs Half Duplex Demo
Transmission Direction:
Multiplexing
• Multiplexing: transmission form allowing multiple
signals to travel simultaneously over one
medium
– Channel logically separated into subchannels
• Multiplexer (mux): combines multiple signals
– Sending end of channel
• Demultiplexer (demux): separates combined
signals and regenerates them in original form
– Receiving end of channel
Relationships Between Nodes
•Point-to-point transmission involves only one transmitter and
one receiver.
•Point-to-multipoint transmission involves one transmitter and
multiple receivers.
Broadcasts involve one transmitter and multiple,
undefined receivers
Nonbroadcast point-to-multipoint transmission issues
signals to multiple, defined recipients
Throughput and Bandwidth
• Throughput: measure of amount of data transmitted during given
time period
• Measured in bits per second, kilobits per second, megabits per
second etc.
• Probably most significant factor in choosing transmission method
• Limited by signaling and multiplexing techniques used in given
transmission method
• Transmission methods using fiber-optic cables achieve faster
throughput than those using copper or wireless connections
• Noise and devices connected to transmission medium can limit
throughput
• Bandwidth: difference between highest and lowest frequencies that
a medium can transmit
• Measured in Hertz or cycles
• 1 Hertz is the measure of a signal from its starting point to it’s
highest amplitude to it’s lowest amplitude and back to the starting
point
Baseband and Broadband
• Baseband: digital signals sent through direct current
(DC) pulses applied to a wire
– Requires exclusive use of wire’s capacity
– Baseband systems can transmit one signal at a time
– Half-duplex or duplex transmission
– Ethernet
• Broadband: signals modulated as radiofrequency (RF)
analog waves that use different frequency ranges
– Does not encode information as digital pulses
– Simplex transmission
Communication Methods Demo
Transmission Flaws: Noise
•
•
•
•
•
Electromagnetic interference (EMI): waves emanating from electrical
devices or cables
Radio frequency interference (RFI): electromagnetic interference caused by
radiowaves
Crosstalk: signal traveling on a wire or cable infringes on signal traveling
over adjacent wire or cable
Certain amount of signal noise is unavoidable
All forms of noise measured in decibels (dB)
Attenuation
Attenuation can be described as the loss of signal strength as the signal flows
away from it’s source. It is caused by resistance on electrical networks and by
optical loss on fiber optic networks.
An analog signal distorted by noise and then amplified
A digital signal distorted by noise and then repeated
Latency
• Delay between transmission and receipt of a signal
– Many possible causes:
• Cable length
• Intervening connectivity device (e.g., modems and
routers)
• Round trip time (RTT): Time for packets to go from
sender to receiver and back
• Cabling rated for maximum number of connected
network segments
• Transmission methods assigned maximum segment
lengths
Network Cables
• A cable is the medium that provides the physical
foundation for data transmission
• Several types of cable are commonly used
• Some networks use only one type of cable, while others
employ several cable types
• The type of cable chosen depends on:
– The size of the network
– The protocols being used
– The network’s physical layout, or topology
Network Transmission Media Demo
New and Old Cables and Connectors Demo
Common Media Characteristics:
Throughput
• Probably most significant factor in choosing
transmission method
• Limited by signaling and multiplexing techniques
used in given transmission method
• Transmission methods using fiber-optic cables
achieve faster throughput than those using
copper or wireless connections
• Noise and devices connected to transmission
medium can limit throughput
Cost
• Many variables can influence final cost of
implementing specific type of media:
– Cost of installation
– Cost of new infrastructure versus reusing
existing infrastructure
– Cost of maintenance and support
– Cost of a lower transmission rate affecting
productivity
– Cost of obsolescence
Noise Immunity
• Some types of media are more susceptible
to noise than others
– Fiber-optic cable least susceptible
• Install cabling away from powerful
electromagnetic forces
– May need to use metal conduit to contain and
protect cabling
• Possible to use antinoise algorithms
Size and Scalability
• Three specifications determine size and
scalability of networking media:
– Maximum nodes per segment
• Depends on attenuation and latency
– Maximum segment length
• Depends on attenuation, latency, and segment
type
• Populated segment contains end nodes
– Maximum network length
• Sum of network’s segment lengths
Connectors and Media Converters
• Connectors are the pieces of hardware that connect the wire to the
network device.
• Every medium requires a specific kind of connector
• Media converter: hardware enabling networks or segments running
on different media to interconnect and exchange signals
– Type of transceiver
• Device that transmits and receives signals
Copper wire-to-fiber media converter
Coaxial Cable
• High resistance to noise; expensive
• Impedance: resistance that contributes to controlling signal
(expressed in ohms)
• Thickwire Ethernet (Thicknet RG-8): original Ethernet medium
– 10BASE-5 Ethernet
• Thin Ethernet (Thinnet RG-58 /U): more flexible and easier to handle
and install than Thicknet
– 10BASE-2 Ethernet
– Coax comes in many types, but their construction is similar: a
central copper core surrounded by an insulator, a braided metal
shielding, and an outer cover called the sheath or jacket
Coaxial Cable Demo
Coaxial Cable Types
The table below describes the different coaxial cable grades.
Grade
Uses
Conductor
Resistance Rating
RG-58
Ethernet networking Tin-coated copper
50 ohms
RG-59
Cable TV
Copper-plated steel 75 ohms
RG-6
Satellite TV
Solid copper
75 ohms
RG-8
Thick Ethernet
Solid copper
50 ohms
Coaxial Connectors
• Connectors: pieces of hardware connecting wire to
network device
– Every networking medium requires specific kind of connector
Connector
BNC
F-Type
F-type connector
Description
•Molded onto the cable
•Used to create Ethernet network connections
•Twisted onto the cable
•Used to create cable and satellite TV
connections
•Used to hook a cable modem to a broadband
cable connection
Connectors Demo
Twisted-Pair Cable
•
•
Twisted-Pair Cable:
Color-coded pairs of insulated copper wires 0.4 to 0.8 mm in diameter,
twisted in pairs around each other and encased in a plastic coating
– The twists in a twisted-pair cable reduce the effect of crosstalk, the
infringement of the signal from one wire pair on another wire pair’s
signal; crosstalk is measured in decibels (dB), a measurement unit
of signal strength of a sound’s intensity
– The number of twists per inch determines how resistant the pair
will be to noise but increases attenuation
– TIA/EIA 568 standard divides twisted-pair wiring into several
categories
– Level 1 or CAT 3, 4, 5, 5e, 6, 6e, 7
– Is the most common form of cabling used on LANs
– Is relatively inexpensive, easy to install, and capable of spanning
significant distances before additional equipment is required
– Can accommodate several different topologies, but is most often
used in a star topology
– Can handle the faster networking transmission rates in use today
– Is available in unshielded, shielded and screened
Twisted Pair Cabling and Connectors Demo
Shielded Twisted-Pair (STP)
• Shielded Twisted-Pair (STP):
– The cable consists of insulated wire pairs that are
surrounded by a metal shielding, such as foil
– The effectiveness of the shield depends on the
environmental noise to which STP is subjected, the
grounding mechanism, and the material, thickness,
symmetry and consistency of the shielding
– STP is more expensive than UTP, but does provide
better immunity to EMI and RFI
UTP (Unshielded Twisted-Pair)
•
•
Less expensive, less resistant to noise than STP
– The cable contains color-coded pairs of
insulated copper wires inside a plastic jacket
– Each pair has a different number of twists per
inch, depending on the grade, to help eliminate
interference from adjacent pairs or cables
Categories:
– CAT 3 (Category 3): up to 10 Mbps of data at
16 MHz
– CAT 4 (Category 4): 16 Mbps throughput at up
to 20 MHz
– CAT 5 (Category 5): up to 1000 Mbps
throughput at 100 MHz
– CAT 5e (Enhanced Category 5): higher twist
ratio 350 MHz
– CAT 6 (Category 6): six times the throughput of
CAT 5. Wires encased in foil. 250 MHz
– CAT 6e (Enhanced Category 6): reduced
attenuation and crosstalk. Capable of 550 MHz.
– CAT 7 (Category 7): signal rates up to 1 GHz.
Contains sheilding and uses different
connectors.
Twisted Pair Connectors
Connector
RJ-11
RJ-45
Description
•Has 4 connectors
•Supports up to 2 pairs of wires
•Uses a locking tab to keep connector secure in outlet
•Used primarily for telephone wiring
•Has 8 connectors
•Supports up to 4 pairs of wires
•Uses a locking tab to keep connector secure in outlet
•Used for Ethernet and some token ring connections
Comparing STP and UTP
• Throughput: STP and UTP can both transmit data at 10,
100, and 1000 Mbps
– Depending on grade of cabling and transmission
method used
• Cost: STP usually more expensive than UTP
• Connector: Both use RJ-45 and RJ-11
• Noise Immunity: STP more noise-resistant
• Size and scalability: Max segment length for both is 100
m on 10BASE-T and 100BASE-T networks
– Maximum of 1024 nodes
TIA/EIA 568A Series
• The T568A wiring standard is
the most popular wiring
standard currently in use for
networks. In the T568A
standard the green wire and
the green and white striped
wire transmits data from the
device, while the orange and
orange and white striped wire
receives data from the
network.
• It typically doesn’t matter
which scheme you choose,
but to avoid confusion and
potential transmission errors
you should ensure that you
cable all wiring on your LAN
according to one standard.
TIA/EIA 568B Series
In the T568B standard
the orange and orange
and white striped wire
transmits data from the
device, while the green
wire and the green and
white striped wire
receives data from the
network.
Crossover Cable
•Crossover cables are used to wire two computer’s network cards together without the
use of a hub/switch or to wire two hubs/switches together through their data ports
(stacking)
•To create a crossover cable wire one end of the cable 568A and the other end 568B
Straight-through Patch Cable Assembly
Instructions
• Strip the cable jacket back about 3/4 of
an inch from the end of the cable
• Sort the pairs so they fit into the
connector in the correct order
• Insert the pairs into the connector
• Crimp the pins with a crimp tool
• Repeat for other end and test cable
Twisted Pair Wiring Tools
Fiber-Optic Cable
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•
Accommodates high bandwidths and long distances
Benefits over copper cabling:
– Nearly unlimited throughput
– Very high resistance to noise
– Excellent security
– Ability to carry signals for much longer distances before requiring
repeaters than copper cable
– Industry standard for high-speed networking
Throughput: transmission rates exceed 10 Gigabits per second
Cost: most expensive transmission medium
Connector: 10 different types of connectors
– Typically use ST SC or MTRJ connectors
Noise immunity: unaffected by EMI
Size and scalability: segment lengths vary from
150 to 40,000 meters
– Optical loss: degradation of light signal after it travels a certain
distance away from its source
Fiber Optic Cable Demo
Fiber Optic Cables
The table below describes the different fiber optic cable types.
Type
Single
Mode
Multimode
Description
•Transfers data through the core using a single light ray (the ray is
also called a mode)
•The core diameter is around 10 microns
•Supports a large amount of data
•Cable lengths can extend a great distance
•Expensive
•Transfers data through the core using multiple light rays
•The core diameter is around 50 to 100 microns
•Cable lengths are limited in distance
Figure 3-33 ST (straight tip) Figure 3-34 SC
(subscriber connector
connector
or standard connector)
Figure 3-35 LC (local
connector)
Figure 3-36 MT-RJ
(mechanical
transfer-register
jack) connector
36
DTE (Data Terminal Equipment) and DCE
(Data Circuit-Terminating Equipment)
Connector Cables
• DTE (data terminal equipment)
– Any end-user device
• DCE (data circuit-terminating equipment)
– Device that processes signals
– Supplies synchronization clock signal
• DTE and DCE connections
– Serial
• Pulses flow along single transmission line
• Sequentially
– Serial cable
• Carries serial transmissions
DTE and DCE Connector Cables
Figure 3-37 DB-9 connector
•
•
•
Figure 3-38 DB-25 connector
RS-232 (Recommended Standard 232)
– EIA/TIA standard
– Physical layer specification
• Signal voltage, timing, compatible interface characteristics
– Connector types
• RJ-45 connectors, DB-9 connectors, DB-25 connectors
RS-232 used between PC and router today
RS-232 connections
– Straight-through, crossover, rollover
Structured Cabling
• Structured cabling specifies standards without
regard for the type of media or transmission
technology used on the network. In other
words, it is designed to work just as well for
10BaseT networks as it does for 100BaseFX
networks.
• Structured cabling is based on a hierarchical
design that divides cabling into subsystems.
• You should be familiar with the principles of
structured cabling before you attempt to
design, install, or troubleshoot an
organization’s cable plant.
• Cable plant: hardware making up enterprisewide cabling system
Structured Cabling
Figure 3-39 TIA/EIA structured cabling in an
enterprise
Cable Design and Management
•
•
Cable plant: hardware making up
enterprise-wide cabling system
Structured cabling: TIA/EIA’s 568
Commercial Building Wiring Standard
– Entrance facilities point where
building’s internal cabling plant
begins
• Demarcation point: division
between service carrier’s
network and internal network
– Backbone wiring or Vertical crossconnect: interconnection between
telecommunications closets,
equipment rooms, and entrance
facilities
– MDF (main distribution frame) also
known as the main cross-connect or
the Equipment room: Interconnection
point between the LAN/WAN and the
service provider’s facility. Location of
significant networking hardware,
such as servers and mainframe
TIA/EIA structured cabling in a building
hosts
Cable Design and Management
– IDF (intermediate distribution
frame) or
telecommunications closet:
contains connectivity for
groups of workstations in
area, plus cross connections
to equipment rooms
– Horizontal wiring: wiring
connecting workstations to
closest telecommunications
closet
– Work area: encompasses all
patch cables and horizontal
wiring necessary to connect
workstations, printers, and
other network devices from
NICs to telecommunications
closet
Horizontal Wiring Subsystem
• Horizontal wiring— Wiring that connects workstations to the closest
telecommunications closet. TIA/EIA recognizes three possible cabling
types for horizontal wiring: STP, UTP, or fiber-optic. The maximum
allowable distance for horizontal wiring subsystem is 100 m. This span
includes 90 m to connect a data jack on the wall to the
telecommunications closet plus a maximum of 10 m to connect a
workstation to the data jack on the wall plus the cross connect.
Patch panel
Patch panel
Horizontal wiring
Wiring Rack
Punchdown block
Patch Panel
“Telco Room”
Only twisted pair can be terminated in the
punch down block.
Data Outlet
Data Outlet
Structured Cabling
TIA/EIA specifications for backbone cabling
Installing Cable
• Many network problems can be traced to poor cable installation
techniques
• Two methods of inserting UTP twisted pairs into RJ-45 plugs:
TIA/EIA 568A and TIA/EIA 568B
• Straight-through cable allows signals to pass “straight through”
between terminations. Straight-through cables are used when
connecting a PC to a Hub or Switch or when connecting Hubs
together through their uplink ports.
• Crossover cable: termination locations of transmit and receive wires
on one end of cable reversed. Crossover cables are used when
connecting a PC directly to another PC without going through a Hub
or when connecting or “stacking” two hubs together through their
data ports.
Summary
• Information can be transmitted via two methods: analog or digital
• In multiplexing, the single medium is logically separated into multiple
channels, or subchannels
• Throughput is the amount of data that the medium can transmit
during a given period of time
• Baseband is a form of transmission in which digital signals are sent
through direct current pulses applied to the wire
• Noise is interference that distorts an analog or digital signal
• Analog and digital signals may suffer attenuation
• Cable length contributes to latency, as does the presence of any
intervening connectivity device
• Coaxial cable consists of a central copper core surrounded by a
plastic insulator, a braided metal shielding, and an outer plastic
cover (sheath)
• Twisted-pair cable consists of color-coded pairs of insulated copper
wires
• There are two types of twisted-pair cables: STP and UTP
Summary (continued)
• There are a number of Physical layer specifications for Ethernet
networks
• Fiber-optic cable provides the benefits of very high throughput, very
high resistance to noise, and excellent security
• Fiber cable variations fall into two categories: single-mode and
multimode
• Structured cabling is based on a hierarchical design that divides
cabling into six subsystems
• The best practice for installing cable is to follow the TIA/EIA 568
specifications and the manufacturer’s recommendations
• Wireless transmission requires an antenna connected to a
transceiver
• Infrared transmission can be used for short-distance transmissions
The End