Chap 8 Design and Documentation Andres, Wen-Yuan Liao Department of Computer Science and Engineering...
-
Upload
cassidy-willoughby -
Category
Documents
-
view
221 -
download
0
Transcript of Chap 8 Design and Documentation Andres, Wen-Yuan Liao Department of Computer Science and Engineering...
Chap 8 Design and Documentation
Andres, Wen-Yuan Liao
Department of Computer Science and Engineering
De Lin Institute of Technology
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 designA logical and a physical topology
Layer 2 LAN topology Reduce congestion and collision
domain size
Layer 3 topologyBreak 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 topologyThe 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 floorAccommodate incoming horizontal c
ables
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, non-switched, 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 closetDrawing a floor plan of the building Adding to it all of the devices that
will be connected to the networkComputers, 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 repeaters100 Ohm UTP (four pair) 150 Ohm STP-A (two pair) 2 fiber (duplex) 62.5/125 µm optical f
iber Multimode optical fiber
MDF location in a multi-story 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 cablingConnect wiring closets to each
other
Backbone cabling mediaTIA/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.
GroundingPrevent 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 deviceThe second hand should remain in your pocket
Avoiding potentially dangerous circuits between
buildings Use fiber-optic cable as the backboneBecause 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 disturbanceUnwanted 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 voltageCaused by overloaded circuits
SpikeAn 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 buildingElevators, 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
InverterConvert 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
BatteriesGenerally, 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 serverShut down files when the UPS
battery power nears its endA 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