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Chap 8 Design and
Documentation
Andres, Wen-Yuan Liao
Department of Computer Science and Engineering
De Lin Institute of Technology
[email protected]
http://www.cse.dlit.edu.tw/~andres
Overview
• Network Design and Documentation
• Document brainstormed ideas,
problem solving matrices
Wiring closet specifications
Wiring and electrical techniques used
in network building
Basic Network Design and
Documentation
General design process
Network design issues
General network design
process
Network design documents
General design process
Layer 1 design
A
logical and a physical topology
Layer 2 LAN topology
 Reduce
congestion and collision
domain size
Layer 3 topology
 Break
up both collision and
broadcast domains.
Network design issues
Gather information about the
organization
Make a detailed analysis and
assessment of the current and
projected requirements
Identify the resources and
constraints of the organization
Network design documents
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
Wiring Closet Specifications
Overview of wiring closet selection
Size
Environmental specification
Walls, floors, and ceilings
Temperature and humidity
Lighting fixtures and power outlets
Room and equipment access
Cable access and support
Overview of wiring
closet selection
MDF:Main Distribution
Facility/Facilities
IDF:Intermediate Distribution
Facilities
Size
The horizontal cabling runs must
be attached to a central point in
a star topology
The central point is the wiring
closet
 Where
the patch panel and the
hub must be installed
Size
TIA/EIA-569
A minimum of one wiring
closet
 Additional wiring closets
for each 1,000 m2

Environmental specification
Power supply and
heating/ventilation/air conditioning
(HVAC) issues
Be secure from unauthorized
access
Meet all applicable building and
safety codes
Walls, floors, and ceilings
Bear the load
 MDF:
4.8 kPA (100 lb/ft²)
 IDF: 2.4 kPA (50 lb/ft²)
Raised floor
 Accommodate
incoming horizontal
cables
Floor coverings should be tile
Temperature and humidity
Maintain a room temperature of
approximately 21° C
No water or steam pipes running
through or above the room, with
the exception of a sprinkler system
Relative humidity should be
maintained at a level between
30%-50%
Lighting fixtures & power outlets
A minimum of two dedicated, nonswitched, AC duplex electrical
outlet receptacles, each on
separate circuits
Florescent lighting should be
avoided for cable pathways
because of the outside
interference that it generates
Room and equipment access
The door of a wiring closet
should be at least .9 m wide,
and should swing open out of
the room, thus ensuring an
easy exit for workers
The lock should be located on
the outside
Room and equipment access
Allow 48 cm for the panel to swing
out from the wall
A distribution rack, then it must
have a minimum 15.2 cm of wall
clearance for the equipment, plus
another 30.5-45.5 cm for physical
access by workmen and repairmen
Cable access and support
If a wiring closet serves as an MDF, all
cable running from it should be
protected by 10.2 cm conduit or
sleeved core
All horizontal cabling that runs from
work areas to a wiring closet should be
run under a raised floor
Cable access and support
Any wall/ceiling openings that
provide access for the conduit,
or sleeved core, must be sealed
with smoke and flame-retardant
materials
Identifying Potential Wiring
Closets
Topology as floor plan
Selecting potential locations
Determining number of wiring
closets
Identification practice
Topology as floor plan
In order to determine the location
of a wiring closet
 Drawing
a floor plan of the building
 Adding to it all of the devices that
will be connected to the network
 Computers, printers and file
servers
Selecting potential locations
Identify secure locations that are
close to the POP
The POP is where
telecommunications services,
provided by the telephone
company, connect to the building's
communication facilities
Determining number of
wiring closets
Use your compass to draw circles: a
radius of 50 m from potential hub
locations
If overlap, eliminate one of the hub
locations
To see if one of them is closer to the
POP than the other(s)
Horizontal and Backbone
Cabling
Catchment area problems
MDF location in a multi-story building
Example of where you would use multiple
wiring closets
Cabling for MDF and IDF connections
Backbone cabling media
TIA/EIA-568-A requirements for backbone
cabling
Maximum distances for backbone cabling
Catchment area problems
If the 100 m catchment area
cannot provide enough coverage,
it can be extended by using
repeaters
 100
Ohm UTP (four pair)
 150 Ohm STP-A (two pair)
 2 fiber (duplex) 62.5/125 µm optical
fiber
 Multimode optical fiber
MDF location in a multistory building
The MDF is usually located on
one of the middle floors of the
building
The POP might be located on
the first floor, or in the
basement
Cabling for MDF and IDF
connections
Backbone cabling: vertical
cabling
 Connect
other
wiring closets to each
Backbone cabling media
TIA/EIA-568-A
 100 Ω UTP (four-pair)
 150 Ω STP-A (two-pair)
 62.5/125 µm multimode optical fiber
 Single-mode optical fiber
The IDF is sometimes referred to as the
horizontal cross-connect (HCC)
The MDF is sometimes referred to as the
main cross-connect (MCC)
Only one
Electricity and Grounding
Differences between AC and DC
AC line noise
Electrostatic discharge
Grounding electrical current in computer
equipment
Purpose of grounding computer
equipment
Safety ground connections
Safety ground connection problems
Differences between AC & DC
DC flows at a constant value
when circuits are turned on
AC rises and falls in current
values
AC line noise
Coming from a nearby video
monitor, or hard disk drive
It does this by adding unwanted
voltages to the desired signals
Prevent a computer's logic gates
from detecting the leading and
trailing edges of the square signal
waves
Electrostatic discharge
ESDs can destroy
semiconductors and data, in a
random fashion, as they shoot
through a computer
A solution that can help solve
problems that arise from ESD is
good grounding
Grounding electrical current
in computer equipment
The safety ground wire is connected to any
exposed metal part of the equipment
The motherboards and computing circuits in
computing equipment are electrically
connected to the chassis
This also connects them to the safety
grounding wire, which is used to dissipate
static electricity.
Grounding
Prevent such metal parts from
becoming energized with a
hazardous voltage
Circuit breakers and Ground Fault
Circuit Interrupters (GFCIs)
Surge suppressors and
Uninterrupted Power Supplies (UPS)
 Be
required to protect computing and
networking equipment
Safety ground connection
problems
The earth ground between
buildings is almost never the
same
Cabling and Grounding
Causes of ground potential problems
Networking devices and dangerous circuits
Faulty ground wiring problems
Avoiding potentially dangerous circuits
between buildings
How fiber optic cable can prevent electrical
shocks
Reasons for using UTP for backbone cabling
between buildings
Causes of ground
potential problems
When devices with different
ground potentials are linked in a
circuit, they can produce
hazardous shocks
Networking devices and
dangerous circuits
The closed circuit produced by the use of
UTP cable would then allow electrical
current to flow from the negative source to
the positive source
One hand rule
You should not use more than one hand at a
time to touch any electrical device
 The second hand should remain in your pocket

Avoiding potentially
dangerous circuits between
buildings
Use fiber-optic cable as the
backbone
Because glass is an insulator
rather than a conductor,
electricity does not travel over
fiber-optic cables
Reasons for using UTP for
backbone cabling between
buildings
Whenever copper is used for
backbone cabling, it can
provide a pathway for lighting
strikes to enter a building
Network Power Supply
Issues: Power Line
Problems
Power problem classifications
Normal mode and common mode
Typical power line problems
Sources of surges and spikes
Surge and spike damage
Surge and spike solutions
Sag and brownout solutions
Oscillation solution
Power problem classifications
Normal mode problem
 Exists
between the hot and neutral
wire
 Do not, ordinarily, pose a hazard to
you or to your computer
 Be intercepted by a computer's power
supply, an uninterruptible power
supply or an AC power line filter
Power problem
classifications
Common mode problem
 If
a situation involves either the
hot, or neutral wire, and the
safety ground wire
 Go directly to a computer's
chassis without an intervening
filter.
Typical power line problems
Power disturbance
 Unwanted
voltage that is sent to
electrical equipment
 Include voltage surges, sags,
spikes, and oscillations
Another situation that can
cause power problems is a total
power loss
Surge
A voltage increase above 110% of
the normal voltage carried by a
power line
A few seconds
Hardware damage
Most computer power supplies that
run at 120 V are not built to handle
260 V for any length of time
Sag/Brownout
A brownout that lasts less than a
second
Voltage on the power line falls
below 80% of the normal voltage
 Caused
by overloaded circuits
Spike
An impulse that produces a voltage
overload on the power line
Spikes last between .5 and 100
microseconds
In simple terms, when a spike occurs it
means that your power line has
momentarily been struck with a
powerful hit of at least 240 V
Oscillations and Noise
Oscillations are also sometimes
referred to as harmonics, or
noise
A common cause of oscillation
is an excessively long
electrical wiring run, which
creates an antenna effect.
Sources of 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
Sources of surges and spikes
Inside your school, office, or
building
 Elevators,
photocopiers, and air
conditioners, cycle on and off, they
create momentary dips and surges
in power
Surge and spike solutions
Surge suppressors
When surges or spikes come in,
surge suppressors divert them to
ground
A good rule of thumb to follow is to
protect all networking devices with
surge suppressors
Surge and spike solutions
If you protect one networking
device with a surge suppressor,
then you should protect all
devices, including the telephone
line, in the same way
Sag and brownout solutions
Every network should have
some type of uninterruptable
power supply
Oscillation solution
The best way to address the
problem of oscillation is to
rewire
Surge Suppressors and
UPS Functions
Surge suppressors: networking device
locations
Surge suppressors: for power panel
locations
UPS: for certain LAN devices
UPS: for certain electrical problems
UPS: components
UPS: differences in UPS features
UPS: description and operation
Surge suppressors:
networking device locations
Surge suppressors are usually
mounted on a wall power socket, to
which a networking device is
connected
A device called a metal oxide
varistor (MOV) is most often used
as this type of surge suppressor
Surge suppressors:
networking device locations
This type of surge suppressor
has a limited lifetime,
dependent, in part, on heat and
usage
Surge suppressors: for
power panel locations
By placing a commercial grade
surge suppressor near the
power panel, the impact on the
network, of voltage surges and
spikes diverted to ground, can
be reduced
UPS: for certain electrical
problems
An UPS is designed to handle only
short-duration power outages
If a LAN requires uninterrupted
power, even during power outages
that could last several hours, then a
generator would be needed to
supplement the backup provided by
a UPS
UPS: components
Inverter
 Convert
low-level DC voltage of the
batteries into the AC voltage, normally
supplied by the power line, to networking
devices
battery charger
 Designed
to keep the batteries in peak
condition during periods when the power
line system is functioning normally
UPS: components
Batteries
 Generally,
the bigger the
batteries in a UPS, the longer a
period of time it will be able to
support networking devices
during power outages
UPS: description and
operation
A good UPS should be designed
to communicate with the file
server
 Shut
down files when the UPS
battery power nears its end
 A good UPS reports instances
when the server starts to run on
battery power
Summary
Document what you have done
A wiring closet
Backbone cabling
Surge suppressors