Sem 1v2

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Sem 1v2 Chapter 8 Design and Documentation
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• Your network design could take into consideration
  many technologies (e.g. token-ring, FDDI, and
  Ethernet),

• Once you have settled on Ethernet, you must
  develop a Layer 1 LAN topology.

• You must determine the type of cable, and the
  physical (wiring) topology that you will use.
• The most common choice is CAT 5 UTP as the
  media, and an extended star topology as the
  physical (wiring) topology.

• Then you must decide on which one, of the several
  types of Ethernet topologies, you need to use.

Two common types of Ethernet are 10Base-T and
100Base-TX (Fast Ethernet).

• You might use hubs, repeaters, and transceivers
  in your design, along with other Layer 1
  components such as plugs, cable, jacks, and patch
  panels.
• To finish Layer 1 design, you must generate both
  a logical and a physical topology.

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• The next step is to develop a Layer 2 LAN
  topology.
• You could add switches to reduce congestion and
  collision domain size. In the future, you may be
  able to afford to replace hubs with switches, and
  more less intelligent Layer 1 devices with more
  intelligent Layer 2 devices.

• The next step, then, is to develop a Layer 3
  topology
• You could use routers to build scalable
  internetworks (larger LANs, WANs, networks of
  networks), or to impose logical structure on the
  network you are designing, or use them for
  segmentation

Your network design should also consider the
placement of such things as file servers,
databases, and other shared resources, as well as
the LAN's link to WANs and to the Internet.

• Finally, you should document your network
  design's physical and logical topologies.

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There are three key aspects to the "Dartmouth
method design process. First, there is the
problem solving cycle, which consists of
Original problem statement. Redefine
problem. Develop general specifications.
Brainstorm alternatives. Select most
viable alternative. Check problem
definition. Redefine and add
specifications. Brainstorm again if
necessary. Reiterate until problem is
appropriate. The second key aspect to their
approach is the problem-solving matrix. This is a
graphical organizer Simply list alternatives
(choices) down the horizontal rows list
specifications across the vertical columns. A
third key aspect of design is brainstorming by
brainstorming we mean a special 2 to 10 minute
session which follows these rules 1. quantity
of ideas 2. no censorship of ideas 3.
building upon others ideas 4. wildest ideas
possible
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• Explain how to start designing a network.
• 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.
• Your first step in the process is to gather
  information about the organization. This
  information should include
• organization's history and current status
• projected growth
• operating policies and management
• procedures
• office systems and procedures
• viewpoints of the people who will be using
  the LAN

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• The second step is to make a detailed analysis
  and assessment of the current and projected
  requirements of those people who will be using
  the network.
• The third step is to identify the resources and
  constraints of the organization. Organization
  resources that can affect the implementation of a
  new LAN system fall into two main categories -
  computer hardware and software resources, and
  human resources.
• The questions you ask should include
• What financial resources does the
  organization have available?
• How are these resources currently linked
  and shared?
• How many people will be using the network?
• What are the computer skill levels of the
  network users?
• What are their attitudes toward computers
  and computer applications?
• Following these steps, and documenting the
  information, will help you estimate costs and
  develop a budget for the implementation of a LAN.
• The final step is to document the information in
  the framework of a formal report.

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• Explain a general network design process.
• In technical fields the design process includes
• designer - person doing the design
• client - person who has requested, and is
  probably paying forthe design
• user(s) - person(s) who will be using the product
  
• brainstorming - generation of creative
  ideas for the design
• specifications development - usually
  numbers which will measure how well the design
  works
• building and testing - to meets client
  objectives and satisfies certain standards

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• Describe the documents that are required for a
  network design.
• The following list includes some of the
  documentation that you should create as you
  design a network
• engineering journal
• logical topology
• physical topology
• cut sheets
• problem-solving matrices
• labeled outlets
• labeled cable runs
• summary of outlets and cable runs
• summary of devices, MAC addresses, and
• IP addresses

9
Give an overview of wiring closet selection,
MDF/IDF selection, and power supply issues.
There are standards governing MDFs and IDFs,
and you will learn some of these standards while
learning how to select the network wiring
closet(s) Finally, there are issues regarding
how the AC power from the electric power company
can have negative effects on our network.
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Describe the proper size for a wiring closet.
EIA/TIA 568-A specifies that, in an Ethernet
LAN, the horizontal cabling runs must be attached
to a central point in a star topology. The
central point is the wiring closet. The size of
the closet will vary with the size of the LAN,
and the types of equipment required to operate
it. the size of the closet will vary with the
size of the LAN, and the types of equipment
required to operate it.
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• Describe the environmental specifications for a
  wiring closet.
• Any location that is selected for a wiring closet
  must satisfy certain environmental requirements,
  which include power supply and HVAC
  (heating/ventilation/air conditioning) issues.
• The location must be secure from unauthorized
  access, and must meet all applicable building and
  safety codes.
• materials for walls, floors, and ceilings
• temperature and humidity
• locations and types of lighting
• power outlets
• room and equipment access
• cable access and support.

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Describe the specifications that apply to walls,
floors, and ceilings. All interior walls, or at
least those on which equipment is mounted, should
be covered with ¾" plywood that is raised a
minimum of 1 ¾" from the underlying wall. The
main distribution facility for the building, then
the telephone point of presence (POP), may also
be located inside the room. Minimum of 15' of
wall space provided for the terminations and
related equipment. Fire retardant paint must be
used on the walls. Rooms selected for wiring
closets must not have a dropped, or false,
ceiling. The MDF required equipment, with a
minimum capability of 250 lbs. per sq. foot.
Where the wiring closet serves as an intermediate
distribution facility (IDF), the floor must be
able to bear a minimum load of 100 lb. per sq.
foot. The room should have a raised floor.
Floor coverings should be tile, or some other
type of finished surface.
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8.2.1.4. Describe the specified standards for
temperature and humidity levels. There should
be no water or steam pipes running through or
above the room, with the exception of a sprinkler
system, which may be required by local fire
codes. Relative humidity should be maintained
at a level between 30 and 50. The wiring
closet should include sufficient HVAC to maintain
a room temperature of approximately 70
Fahrenheit.
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8.2.1.5. Describe the requirements for
lighting fixtures and power outlets. A wall
switch should be placed immediately inside the
door. Fluorescent lighting should be avoided
because of the outside interference that it
generates. If there is only one wiring closet
in a building, or if the closet serves as the
main distribution facility, there should be at
least one duplex power outlet positioned every
10 along each wall of the room. If the
wiring closet serves as an IDF, then there should
be at least two duplex power outlets located
along each wall.
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8.2.1.6. Describe the requirements for room
and equipment access. The door of a wiring
closet should be at least 3' wide, and should
swing open out of the room, The lock should be
located on the outside of the door, but allow
anyone who is on the inside to exit at any time.
A wiring hub and patch panel may be mounted to a
wall with a hinged wall bracket, or with a
distribution rack.
If the choice is a distribution rack, then it
must have a minimum 6" of wall clearance for the
equipment, plus another 12"-18" for physical
access by workmen and repairmen. A 22" floor
plate, used to mount the distribution rack,
Full equipment cabinet, they require at least 30"
of clearance in front, in order for the door to
swing open. Typically, such equipment cabinets
are 72" high, 29" wide, and 26" deep.
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Design and Documentation 8.2.1.7.
Describe the specifications for cable access and
support.
If a wiring closet serves as a MDF or IDF, all
cable running to it or from should be protected
by 4" conduit or sleeved core.
A minimum of two excess sleeved cores or conduits
should be kept in each wiring closet. All conduit
and sleeved core should be kept to within 6" of
the walls.
All horizontal cabling that runs should be run
under a raised floor. The cabling should be
run through 4" sleeves that are placed above door
level. In order to ensure proper support, the
cable should run from the sleeve directly onto a
12" ladder rack in the room.
Conduit, or sleeved core, must be sealed with
smoke and flame retardant materials that meet all
applicable codes.
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Describe the first step in locating a wiring
closet for an Ethernet star topology.
The first step in locating a wiring closet is to
obtain, or create, to-scale floor-plans of the
area the network will service. Locating all the
deices that will be connected to the network.
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8.2.2.2. Describe how to select potential
locations for wiring closets.
A good place for a potential wiring closet
location is to identify secure locations that
are close to the POP, that can serve as the main
distribution facility. The POP is where
telecommunications facilities, provided by the
telephone company connect to the building's
communication facilities, it is essential that
the hub be located near it in order to facilitate
wide area networking and connection to the
Internet.
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8.2.2.3. Describe how to determine the
necessary number of wiring closets.
LANS that cover a large geographic area may need
more than one wiring closet. When this occurs,
one wiring closet must be designated as the main
distribution facility (MDF). Any additional
wiring closets are referred to as intermediate
distribution facilities (IDFs).
After you have drawn in all of the devices that
are to be connected to your network, on a floor
plan, The next step is to determine how many
wiring closets you will need to serve the area
covered by the network. You will use your site
map to do this. Use your compass to draw
circles that represent a radius of 50 m. Each
of the network devices you depicted on your
floor plan should fall within one such circle.
Overlap of circles may remove a catchment
area. Are there any potential hub locations
whose catchment areas can contain all of the
devices that are to be connected to the network
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8.2.2.4. Perform potential wiring closet
identification Describe your task.
Answer the following questions 1. Do any
of the circles overlap? 2. Can any of the
potential wiring closet locations be eliminated?
3. Do any of the circles provide coverage
for all of the devices that will be connected to
the network? 4. Which of the potential
wiring closet locations seems to be the best?
5. Are there any circles where only a few of the
devices fall outside the catchment area? 6.
Which potential wiring closet is closest to the
POP? 7. Based on your findings, list the
three best possible locations for wiring closets.
8. Based on your findings, how many wiring
closets do you believe will be required for
this network?
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8.2.3.1. Describe the building in which you
will install the LAN.
The building in which you will install the LAN
will provide work stations for 71 workers, and
will include seven printers. The description of
the building is as follows The building
occupies 7,200 sq. ft. of office space, all on a
single floor. The building is 60' wide x 120'
long. The ceiling height in all rooms, unless
otherwise specified, is 12'. All ceilings are
dropped ceilings, unless otherwise specified.
All floors are poured concrete covered with
industrial carpet, unless otherwise specified.
All heating and cooling in the building is
supplied by a forced air system..
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8.2.3.2. Describe the potential of wiring
closet "A".
8.2.3.3. Describe the potential of wiring
closet "B".
8.2.3.4. Describe the potential of wiring
closet "C".
8.2.3.5. Describe the potential of wiring
closet "D".
8.2.3.6. Describe the potential of wiring
closet "E".
8.2.3.7. Describe the potential of wiring
closet "F".
8.2.3.8. Describe the potential of wiring
closet "G"
8.2.3.9. Describe the potential of wiring
closet "H"
8.2.3.10. Describe the potential of wiring
closet "I".
8.2.3.11. Describe the potential of wiring
closet "J".
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8.3.1.1. Describe what happens when the
catchment area of a wiring closet is not large
enough.
Unlike the prior example for choosing a wiring
closet, many buildings will require cable runs
greater that 100 meters. This necessitates the
use of repeaters, or multi-port repeaters called
hubs, and the use of IDFs. Emphasize to the
students that these requirements are a matter of
both technology (the network will not work
properly if the rules are violated) and standards
(networks must be built according to various
standards).
EIA/TIA-568 specifies the use of CAT 5 UTP for
all horizontal cabling, when an Ethernet LAN
uses a simple star topology.
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8.3.1.2. Describe the location of the MDF in a
multi-story building.
Typically, the main hub, of an extended star
topology Ethernet LAN, is centrally located.
So important is this central location, that in
a high rise building, the MDF is usually located
on one of the middle floors of the building, even
though the POP might be located on the first
floor, or in the basement.
Backbone cabling (red lines) connects the POP to
the MDF. Backbone cabling is also used to connect
the MDF to the IDFs
Horizontal cabling runs (blue lines) radiate out
from the IDFs on each floor,
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8.3.1.3. Name another example of where you
would use multiple wiring closets.
Another example of a LAN, that would probably
require more than one wiring closet, would a
multi-building campus.
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8.3.1.4. Describe the type of cabling that
connects the IDFs to the MDF.
The IDF to MDF connections are called "backbone"
cabling. There are specific EIA/TIA-568
standards The type of cabling that EIA/TIA-568
specifies for connecting wiring closets to each
other is called backbone cabling. Sometimes you
may see backbone cabling referrred to as vertical
cabling. Backbone cabling consists of the
following backbone cabling runs
intermediate and main cross-connects
mechanical terminations patch cords used
for backbone-to-backbone cross-connection
vertical networking media between wiring
closets on different floors
networking media between the MDF and the POP
networking media used between buildings in
a multi-building campus
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Describe the type of networking media that you
would use for backbone cabling.
Acceptable choices for backbone cabling are UTP
or optical fiber. Most backbones installed today
use optical fiber, for its immunity to EMI/RFI,
lack of grounding problems, extremely long cable
runs, and extremely high bandwidth.
EIA/TIA-568 specifies four types of networking
media that can be used for backbone cabling.
These include 100 Ohm UTP 150 Ohm
UTP 62.5/125 µ optical fiber
single-mode optical fiber Although EIA/TIA-568
recognizes 50 W coaxial cable, generally, it is
not recommended for new installations.
Most installations today use the 62.5/125 µ
fiber-optic cable, as a matter of course, for
backbone cabling.
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Explain how EIA/TIA-568 requirements for backbone
cabling impact the topology.
Three more acronyms --are introduced in the
context of the EIA/TIA-568 standards. MCC (Main
Cross Connect) ICC (Intermediate Cross
Connect) HCC (horizontal cross connect) The
topology that is used is the extended star
topology. Because more complex equipment is
located at the most central point in an extended
star topology, sometimes it is referred to as a
hierarchical star topology.
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There are two ways in which an intermediate
distribution facility can be connected to the
main distribution facility. In the first, each
intermediate distribution facility can be
connected directly to the main distribution
facility. In this case, because the IDF is
where the horizontal cabling connects to a
patch panel in the wiring closet, whose backbone
cabling then connects to the hub in the main
distribution facility, the IDF is sometimes
referred to as the horizontal cross-connect
(HCC). The main distribution facility is
sometimes referred to as the main cross-connect
(MCC), because it connects the backbone cabling
of the LAN to the Internet.
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A second method of connecting an IDF to the
central hub uses a "first" IDF interconnected to
a "second" IDF. The "second" IDF is then
connected to the MDF. In such instances, the IDF
that connects to the work areas is called the
horizontal cross-connect, and the IDF which
connects the horizontal cross-connect to the MDF
is called the intermediate cross-connect (ICC).
Note that no work areas or horizontal wiring
connects to the intermediate cross-connect when
this type of hierarchical star topology is used.
EIA/TIA-568 specifies that no more than one
intermediate cross-connect can be passed through
to reach the main cross-connect.
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Describe the EIA/TIA-568 specifications for
maximum distances of backbone cabling. The
maximum backbone lengths for single-mode optical
fiber (3000m), multimode optical fiber (2500m),
and UTP (90m) are presented. Note the 3km
distance of optical fiber allows it to be used in
a area greater than many high school and junior
college campuses.
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8.3.2.1. Explain the difference between AC and
DC.
The rise and fall of the current values in AC.
The current value remains constant in DC.
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8.3.2.2. Describe how AC line noise creates a
problem. One of the ways AC power line noise
creates problems is by coupling into the media
and distorting digital signals. Other forms of
noise also cause problems on the networking
medium.
You will discover as you work with networks, that
AC line noise, coming from a nearby video
monitor, or hard disk drive, can be enough to
create errors in a computer system. It does
this by burying the desired signals and
preventing a computer's logic gates from
detecting the leading and trailing edges of the
square signal waves. This problem can be
further compounded when a computer has a poor
ground connection.
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8.3.2.3. Explain how electrostatic discharge
can create problems. If students are to be
installing NICs or RAM they should be
particularly aware of the potential problem of
ESD (ElectroStatic Discharge).
You know from experience, that such ESDs can
sting momentarily, but in the case of a computer
such shocks can be disastrous. ESDs can destroy
semiconductors, and data, in a random fashion, as
they shoot through a computer.
One solution to prevent electrostatic discharge,
is good grounding.
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8.3.2.4. Describe how to ground electrical
current in computer equipment.
For both alternating (AC) and direct current (DC)
electrical systems, the flow of electrons is
always from a negatively charged source to a
positively charged source.
Conductors
Insulators.
The safety ground wire is always connected to
any exposed metal parts of the equipment. In
computer equipment, motherboards and computing
circuits are electrically connected to the
chassis, and therefore to the safety grounding
wire. This ground is used to dissipate static
electricity.
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8.3.2.5. Explain the purpose of grounding
computer equipment.
The purpose of connecting the safety ground to
the exposed metal parts of the computing
equipment is to prevent such metal parts from
becoming energized with a hazardous voltage that
may occur as a result of a wiring fault inside
the device.
8.3.2.6. Describe, and explain the function
of, the safety ground connection. What should
be emphasized here is that electricity presents a
hazard to a person should that person become
part of an electrical circuit. Human beings
conduct electricity, and if they should
accidentally become part of a live electrical
circuit, they can be harmed. The purpose of
safety ground connections is to hopefully form a
different circuit, of less resistance the
unfortunate human, so that electron take the path
of least resistance (to ground) and not through
the human's body.
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8.3.2.7. Describe the types of situations in
which a safetyground connection would not be
sufficient. The interesting situation of
multiple grounds is introduced. Although the
complete theory of how this occurs is beyond the
scope of the class, there are a few key features
to note. Ground is our reference voltage, that
which we call zero volts. All voltages are
measurements from one point relative to another
typically relative to ground since that is our
chosen reference point. But what happens when
there is a voltage between two physically
distinct areas (two buildings or two floors in a
building) that we are calling ground? Well
nothing would occur if no circuits where formed
involving these two different grounds. However,
recall we are often running long conducting
copper cables around the floors of the building
or between buildings to build our network.
These provide ways to form complex circuits
involving the different grounds and conducting
human beings or conducting electronic devices.
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8.3.3.2. Explain how network devices, placed
in separate buildings could create a dangerous
circuit. The way that Cat 5 UTP (or any
copper-based conductor) causes different earth
grounds to be a problem is illustrated.
A good way to avoid having current pass through
the body, and through the heart, is to use the
"one-hand" rule. Simply put, this rule says
that you should not use more than one hand at a
time to touch any electrical device. The second
hand should remain in your pocket.
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8.3.3.3. Describe the problems that could
arise because of faulty ground wiring. The
scenario where a difference in voltage exists
between the network cabling and the chassis of an
electronic device is described. Again, the
problem is a human becoming part of an unintended
circuit. When everything works correctly,
according to IEEE standards, there should be no
voltage difference between the networking media
and the chassis of a networking device.
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Explain how to avoid creating potentially
dangerous circuits between buildings. The use
of optical fiber -- which is electrically
insulating (non-conducting) -- is proposed as a
way to avoid creating potentially dangerous
circuits between building. Since
inter-building cabling is typically backbone
cabling anyway, and since today most
installations choose optical fiber as their
backbone medium, this requirement does not
present much of a problem.
8.3.3.6. Explain other types of problems that
can be facilitated by the use of UTP for backbone
cabling between buildings. As if the earth
ground issue wasn't enough reason to discourage
the use of copper-based media between buildings,
another reason is presented. Lightning strikes
can more efficiently couple into buildings, their
networks, and their power systems if there is a
copper conductor between buildings. The lesson
is to just use fiber between buildings!
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8.3.4.1. Describe your task for design
practice.
Provide a plan to network the computing devices,
in all three buildings, in an Ethernet extended
star topology. As you develop your networking
plan, assume that two computing devices are
located in each numbered room. Your plan should
show each of the following 1.location of the
MDF 2.location and number of IDFs
3.identity of IDFs used as horizontal
cross-connects 4.identity of IDFs used as
intermediate cross-connects 5.location of all
backbone cabling runs between MDF and IDFs
6.location of any backbone cabling runs between
IDFs 7.location of all horizontal cabling
runs from IDFs to work areas
42
8.3.5.1. Describe the building.
In order to learn how multiple earth grounds can
impact a LANs wiring scheme, assume that you have
been asked to prepare a wiring plan for a twenty
story building. Three companies occupy the
building Company A occupies the first fifteen
floors. Company B occupies the sixteenth,
seventeenth, and eighteenth floors. Company C
occupies the nineteenth and twentieth floors.
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8.4.1.1. Explain the classifications of power
problems. The definitions of normal mode and
common mode electrical problems are introduced.
Remember that all voltages (electrical
potential differences) are measured between two
points, so you must define what those two points
are when discussing potential voltage problems.
If a situation exists between the hot and neutral
wire, this is referred to as a normal mode
problem. If a situation involves either the
hot, or neutral wire, and the safety ground wire,
it is referred to as a common mode problem.
44
8.4.1.2. Explain which is the greater hazard
to safety and data, normal mode or common mode.
Common mode problems are identified as the
more serious of the two types of power
connection problems because they go directly to
the computer chassis.
45
8.4.1.3. Describe some typical power line
problems.
Surge A surge is a voltage increase above 110
of the normal voltage carried by a power line.
Sag A sag is a brownout that lasts less than a
second. These incidents occur when voltage on the
power line falls below 80 of the normal
voltage. Spike A spike is an impulse that
produces a voltage overload on the power line
that last between .5 and 100 microseconds. When a
spike occurs it means that your power line has
momentarily been struck with a powerful hit of
at least 240 V. Oscillation Oscillations are
also sometimes referred to as harmonics, or
noise. A common cause of oscillation is an
excessively long electrical wiring run
46
8.4.1.4. Describe the sources or surges and
spikes.
There are numerous sources of electrical surges
and spikes. Probably the most common one is a
nearby lightning strike.
Utility switching operations performed by the
local power company can also trigger electrical
surges and spikes.
Equipment such as elevators, photocopiers, and
air conditioners,, cycle on and off, they create
momentary dips and surges in power
47
8.3.2.5. Explain the purpose of grounding
computer equipment.
The purpose of connecting the safety ground to
the exposed metal parts of the computing
equipment is to prevent such metal parts from
becoming energized with a hazardous voltage that
may occur as a result of a wiring fault inside
the device.
48
8.4.1.5. Describe the damage that can occur
because of surges and spikes. A spike or a
surge can wreak havoc on any type of sensitive
electronic equipment. including networking
devices. Consequences of electrical surges and
spikes can be severe. Possibilities include
lockups, loss of memory, problems in retrieving
data, altered data and garbling. Some of the
damage that can occur because of surges and
spikes is introduced. One thing that wasnt
mentioned is actual destruction of the electronic
equipment.
49
8.4.1.6. Describe the solution(s) for the
problems of surges and spikes. Surge
suppressors for all devices connected to the LAN
(PCs, hubs, switches, routers) are recommended as
a defense against surges and spikes.
As a general rule therefore, consider the
telephone line to be part of the network. If one
networking device is protected by a surge
suppressor, then all devices, including the
telephone line, should be protected in the same
way.
50
8.4.1.7. Describe the solution(s) for the
problems of sags and brownouts.
Uninterruptible power supplies (UPS) are
presented as the solution to sags and brownouts
(where the power company sine wave has too low an
amplitude).
A drop in AC power may cause only the faintest
flicker of your electric lights, however, the
same drop in power can be devastating to your
data.
51
8.4.1.8. Describe the solution for the
problems of oscillation. The best way to
address the problem of oscillation is to
rewire. Although this may seem to be an
extreme and expensive solution, it is the
probably the only reliable way you can ensure
completely clean, direct, power and ground
connections.
52
Explain the effectiveness of surge suppressors
when they are located close to networking
devices.
Surge suppressor mounted on a wall power socket.
This type of surge suppressor has circuitry that
is designed to prevent surges and spikes from
damaging the networking device. A device
called a metal oxide varistor (MOV) it most often
used as this type of surge suppressor. An MOV
protects the networking devices by redirecting
excess voltages, that occur during spikes and
surges, to a ground. Simply put, a varistor is
a device that is capable of absorbing very large
currents without damage. An MOV can hold voltage
surges on a 120 V circuit to a level of
approximately 330 V.
Describe the best type of surge suppressor, and
where it should be located. A commercial grade
surge suppressor installed at the power
distribution panel is the recommended solution
to surges and spikes.
53
8.4.2.3. Describe which networking devices
should be supported by an uninterruptable power
supply.
The problem of sags and brownouts can best be
addressed by the use of uninterruptable power
supplies (UPS).
At a minimum, every network file server should
have a source of backup power. Where power
wiring hubs bridges and routers are used, power
backup must be provided to them in order to avoid
failures in the system. An online UPS can
reduce the transfer time to zero.
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8.4.2.4. Describe the kinds of power outages
that a UPS will handle. The utility of UPS for
short-duration power events is described.
Longer-term power disruptions typically exceed
the capacity of UPS, so a backup generator would
be required as well. For most LANs, the
protection offered by a UPS will be more than
accurate. But if a network had human lives,
important government communications, or financial
transactions travelling on it, then it may be
intolerable to have a few hours of network
downtime and a backup generator would be
necessary.
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8.4.2.5. Describe the components of a typical
UPS.
A UPS consists of batteries, a battery charger,
and a power inverter.
In any event, a good UPS should be designed to
communicate with the file server. This is
important so that the file server can be warned
to shut down files when the UPS battery power
nears its end. Additionally, a good UPS reports
instances when the server starts to run on
battery power, and supply this information to
any work stations running on the network, after
the power outage has occurred. The END