Transcript Lecture Five - Personal Web Server

Lecture Five
LAN hardware
COAXIAL CABLE
UTP and Optical Fiber
LAN Design Step 1
Standards
LAN Hardware
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The basic hardware components that are
required to operate a local area network
are:
 work stations
 the networking media
 NIC cards
 a hub or wiring center.
 Server
 Server: Node or software program that
provides services to clients.
A file server
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File servers are PCs.
File servers operate at higher rates of speed and
are the most powerful PCs on networks. In
short.
File servers act as central data repositories and
as central repositories for network application
programs.
most file servers are only responsible for retrieval
of information
they cannot generate information or perform the
type of computations associated with data bases.
Workstations
the networking media?
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media that connects the file server and
workstations.
There are four types of networking media
that can be used:
unshielded twisted pair cable,
shielded twisted pair cable,
coaxial cable, and fiber-optic cable.
NIC cards
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Network interface card or NIC card is where the
physical or MAC address is located.
It is where a device connects to the media and is
located at the data link layer of the OSI model.
On a LAN every workstation and file server has a
NIC card.
Located inside these devices, the NIC card is
designed to plug into one of the expansion slots
on the motherboard.
a hub or wiring center
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Usually, the term hub is used to describe a
network device that serves as the center
of a star-topology network
 hubs can also be understood to be
hardware devices that contain multiple
independent but connected modules of
network equipment.
 In Ethernet where hubs act as multiport
repeaters
What can contribute to degradation of the
signal on the networking media?
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To ensure optimal performance, it is important for the
network media to carry the signal from one device to
another with as little degradation as possible.
In networking, there are several factors that can cause the
signal to degrade. Some of these factors are internal.
Others are external.
Inside copper wires factors such as opposition to the flow
of electrons (resistance), opposition to changes in voltage
(capacitance), and opposition to changes in current
(inductance) can cause signals to degrade.
External sources of electrical impulses that can attack the
quality of electrical signals on the cable include lighting,
electrical interference etc
What causes EMI and RFI to
occur?
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Each wire in a cable can act like an antenna.
When this happens, the wire actually absorbs
electrical signals from other wires in the cable
and from electrical sources outside the cable.
If the resulting electrical noise reaches a high
enough level, it can become difficult for NIC cards
to discriminate the noise from the data signal.
When electrical noise on the cable originates
from signals on other wires in the cable, this is
known as crosstalk.
What is cancellation?
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When electrical current flows through a wire, it
creates a small, circular magnetic field around
the wire.
The direction of these magnetic lines of force is
determined by the direction in which current
flows along the wire.
If two wires are part of the same electrical circuit,
electrons flow from the negative voltage source
to the destination along one wire and from the
destination to the positive voltage source along
the other wire.
Cancellation
What other factors contribute to
signal loss and interference?
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A complex electrical characteristic
involving resistance, or the opposition to
the flow of electrons, and reactance, or the
opposition to changes in voltage
and current, is known as impedance.
 For optimal network performance, it is
important that the network media have a
specific impedance in order to match the
electrical components in the NIC cards.
What types of factors influence the
selection of the network media?
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The type of connecting material used by a
network will determine things such as how much
data and how fast the data can travel across the
network.
While factors such as how much data and how
fast the data can be moved across the network
are important in determining what type of network
media to use, other factors such as expense and
where the cable will be used are important as
well.
n addition, network media can differ in the type of
cable jacket they employ. Simply put, the jacket is
the outside covering of the cable.
What are some advantages
of using coaxial cable?
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Coaxial cable consisted of a hollow outer cylindrical
conductor that surrounds a single inner wire conductor.
Coaxial cable consists of two conducting elements.
One of these is located in the center of the cable and is
copper. conductor.
This center copper conductor is surrounded by a layer of
flexible insulation.
Over this insulating material is a shield composed of woven
copper braid or metallic foil that acts as the second wire in
the circuit.
As its name implies this outer braid acts as a shield for the
inner conductor. Thus, it can help reduce the amount of
interference. Outside this shield is the cable jacket.
What are some disadvantages of
using coaxial cable?
Coaxial cable is available in
different thicknesses.
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As a general rule, the thicker the cable, the more
awkward it is to work with.
This is an important point to remember especially
if cable must be pulled through existing conduits
and troughs that are limited in size.
As a general rule of thumb, the more difficult
network
media is to install, the more expensive it will be to
install.
And, in fact, coaxial cable is more expensive to
install than twisted-pair cable.
Thinnet and Cheapernet
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Thinnet - Term used to define a thinner,
less expensive version of the cable
specified in the IEEE 802.3 10Base2
standard.
 Cheapernet - Industry term used to refer to
the IEEE 802.3 10Base2 standard or the
cable specified in that standard
What is unshielded twisted
pair cable?
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unshielded twisted pair cable, or UTP, is a
four-pair wire medium used in a variety of
networks.
 More specifically, unshielded twisted pair
cable is composed of pairs of wires.
 Each pair of wires is insulated from the
other pairs. Unshielded twisted pair cable
relies solely on the cancellation effect
produced by the twisted wire pairs to limit
signal degradation caused by EMI and RFI
Network type
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A network said to have an ARCnet
architecture would use one set of
standards, while one having a Token Ring
architecture would use another set of
standards.
Token Ring
of using unshielded twisted
pair cable?
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Unshielded twisted pair cable is easy to
install and is less expensive than other
types of networking media.
 In fact, UTP costs less per foot than any
other type of LAN cabling.
i
RJ connector
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a good, solid connection is practically guaranteed. Because
of this, potential sources of network noise can be greatly
reduced.
What are some disadvantages of
using unshielded twisted pair cable?
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Generally speaking, unshielded twisted
pair cable is more prone to electrical noise
and interference than other types of
networking media.
 Once, it could be said that UTP was not as
fast at transmitting data as other types of
cable are.
 However, this is no longer true. In fact,
UTP today is the fastest copper based
media
What are some disadvantages of using
unshielded twisted pair cable?
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Generally speaking, unshielded twisted
pair cable is more prone to electrical noise
and interference than other types of
networking media.
 Once, it could be said that UTP was not as
fast at transmitting data as other types of
cable are.
 However, this is no longer true. In fact,
UTP today is the fastest copper based
media
Network using UTP
What is shielded twisted pair
cable?
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Shielded twisted pair cable, or STP,
combines the techniques of shielding,
cancellation, and twisting of wires.
As specified for use in Ethernet network
installations, 100 ohm shielded twisted pair cable
when properly installed, provides greater
resistance to both electromagnetic interference
and radio frequency interference without
significantly increasing the weight or size of the
cable.
Another type of shielded twisted pair cable is
specified for Token Ring installations. In this type
of STP cable, known as 150 ohm STP,
What are some advantages and
disadvantages of using shielded twisted pair
cable?
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Shielded twisted pair cable has all of the
advantages and disadvantages of
unshielded twisted pair cable.
 In addition, STP affords greater protection
from all types of external interference than
unshielded twisted pair cable.
 Moreover, generally speaking, shielded
twisted pair cable is more expensive than
unshielded twisted pair cable.
What is fiber-optic cable?
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fiber-optic cable is a networking medium
capable of conducting modulated light
transmissions.
 compared with other networking media,
fiber-optic cable is more expensive.
 However, on the plus side, fiber-optic
cable is not susceptible to
electromagnetic interference, and it is
capable of higher data rates than the other
types of networking media.
What are some of the advantages
of using fiber-optic cable?
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Not only is fiber-optic cable unaffected by
electromagnetic interference, it is completely
immune from crosstalk and radio frequency
interference as well.
Because of this freedom from internal and
external noise, signals can go farther and faster
when fiber-optic cable is used.
Since it cannot carry electrical signals, it is ideal
for connecting buildings that might have different
electrical grounds.
Where long cable spans of copper cable between
buildings could serve as an entry point for lightning strikes,
fiber-optic cable used in the same type of situation will not.
Where is fiber-optic cable
typically used?
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While fiber-optic cable has many benefits, its cost
makes it hard to justify its extensive use in most
network installations.
Certainly, the cost of running fiber-optic cable to
every desktop would be prohibitive!
Therefore, today in most networks, the use of
fiber is restricted to cabling runs between
buildings and as the backbone between wiring
hubs
What are the steps in LAN
design and implementation?
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For a LAN to be effective and serve the
needs of its users, it should be
implemented according to a planned
series of systematic steps.
 The four steps you will be following as
you complete this course are study,
selection and design, implementation, and
operation
What activities occur during the
investigation and analysis phase of step
one?
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During step one, information is gathered about
the organization. This information includes the
organization's history and current status,
projected growth, operating policies and
management procedures, office systems and
procedures, and the viewpoints of the people who
will be using the LAN.
Next during the investigation and analysis phase
of step one, the issues or problems that need to
be addressed are defined. Ideally, the information
gathering process will help clarify and identify
what these problems are.
Design (2)
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Another component of the investigation and analysis phase is
assessing the user requirements. A local area network
incapable of supplying prompt and accurate information to its
users is of little use. Therefore, special care must be taken to
ensure that the information requirements of the organization
and its workers are satisfied. Detailed analysis of current and
projected needs will help meet this need.
A fourth part of the investigation and analysis phase of step
one focuses on identifying the resources and constraints of the
organization. Organization resources that can impact the
implementation of a new LAN system fall into two general
categories: computer hardware and software resources and
human resources. An organization's existing computer
hardware and software must be documented and projected
hardware and software needs identified. How are these
resources currently linked and shared? What financial
resources does the organization have available? Documenting
these types of things will help estimate costs and develop a
budget for the LAN.
Standard
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IEEE - Institute of Electrical and Electronics
Engineers. Professional organization whose
activities include the development of
communications and network standards.
IEEE 802.3 - IEEE LAN standard that specifies an
implementation of the physical layer and the MAC
sublayer of the data link layer. IEEE 802.3 uses
CSMA/CD access at a variety of speeds over a
variety of physical media. Extensions to the IEEE
802.3 standard specify implementations for Fast
Ethernet. Physical variations of the original IEEE
802.3 specification include 10Base2, 10Base5,
10BaseF, 10BaseT, and 10Broad36. Physical
variations for Fast Ethernet include 100BaseT,
100BaseT4, and 100BaseX.
Standard (2)
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IEEE 802.5 - IEEE LAN standard that specifies an
implementation of the physical layer and MAC sublayer of
the data link layer. IEEE 802.5 uses token passing access at
4 or 16 Mbps over STP cabling and is similar to IBM Token
Ring.
IEEE 802.5 - IEEE LAN standard that specifies an
implementation of the physical layer and MAC sublayer of
the data link layer. IEEE 802.5 uses token passing access at
4 or 16 Mbps over STP cabling and is similar to IBM Token
Ring. See also Token Ring.
EIA/TIA-569 - Standard that defines and describes
horizontal pathways, telecommunications closets,
backbone pathways, equipment rooms, work stations, and
entrance facilities for local area network systems and,
where applicable, the minimum requirements for them.