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Network Design Issues

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Title: Network Design Issues


1
Network Design Issues
  • Design and Documentation
  • Semester 1, Ch. 8

2
Content
  • Network design and documentation.
  • Planning structured cabling.
  • Design practices.
  • Electricity and grounding.
  • Network power supply.

3
General design process
  • Develop a Layer 1 LAN topology
  • The type of cable (fiber, coaxial, CAT 5 ).
  • The physical (wiring) topology.
  • Types of Ethernet topologies.
  • Hub, repeater, closet, patch panel ...
  • Develop a Layer 2 LAN topology
  • To add Layer 2 devices to your topology to
    improve its capabilities.
  • Develop a Layer 3 LAN topology
  • Build scalable inter-networks.
  • Link to WANs.

4
Network Design Issues
  • Gather information about the organization
  • Make a detailed analysis and assessment of the
    current and projected requirements of those
    people who will be using the network.
  • Identify the resources and constraints of the
    organization.
  • Financial
  • Human Resources
  • Skill level of users
  • Attitudes of users towards technology
  • Documentation for cost estimates, budgeting

5
Problem-solving matrices
6
Documentation needed 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

7
Wiring Closets (TIA/EIA 568-A)
  • Main Distribution Facility (MDF)
  • Intermediate Distribution Facility (IDF)
  • Horizontal cabling runs must be attached to a
    central point in star topology (the wiring
    closet, where the patch panels, hubs, etc. are
    installed)

8
Wiring Closets (TIA/EIA 569)
  • Each floor must have at least one (1) wiring
    closet and additional wiring should be provided
    when the floor area exceeds 1000 square meters.

9
Wiring Closet Specifications
10
Wiring Closet SpecificationEnvironmental
Specification
  • Any room, or closet that you choose to serve as a
    wiring closet should adhere to guidelines
    governing such items as the following 
  • materials for walls, floors, and ceilings
  • temperature and humidity
  • locations and types of lighting
  • power outlets
  • room and equipment access
  • cable access and support

11
Walls, Floors Ceilings
  • Any openings for conduits or sleeved cores must
    be sealed with smoke and flame retardant
    materials
  • All cable leaving the room to IDFs, etc. should
    be via a 10.2cm sleeved core or conduit.

12
Walls floors and ceilings
  • Rooms must not have a dropped, or false, ceiling.
  • If MDF POP may be located inside the room. The
    interior wall of the POP site, behind the PBX,
    should be covered from floor to ceiling with 20mm
    plywood, with minimum of 4.6 m of wall space
  • Fire-prevention materials should be used during
    construction.
  • NO false or dropped ceiling

 20mm A-C plywood that is at least 2.4m high.
30.5 cm
  • MDF 100 lb/ft2
  • IDF 50 lb/ft2
  • If possible, should be Raised tiled floor or some
    other type of finished surface. (to control dust
    and minimize ESD)

13
Temperature and Humidity
  • Temperature should be maintained at 21C when all
    equipment is in operation
  • Humidity should be maintained between 30-50.
  • no water or steam pipes running through or above
    the room, with the exception of a sprinkler
    system.
  • Failure to maintain these standards could result
    in UTP wiring corrosion.

14
Lighting fixtures/power outlets
  • If the closet serves as the MDF - minimum of two
    dedicated, non-switched AC duplex electrical
    outlet receptacles, each on separate circuits.
  • It should also have at least one duplex power
    outlet positioned every 1.8 m along each wall of
    the room, and should be positioned 150 mm above
    the floor.
  • A wall switch, that controls the rooms main
    lighting, should be placed immediately inside the
    door.
  • Lighting requirements for a telecommunications
    closet specify a minimum of 500 lx (brightness of
    light equal to 50 foot candles), and that light
    fixtures be mounted a minimum of 2.6 m above the
    floor.
  • Fluorescent lighting may be used if installed
    properly but they are not preferred.

15
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.
  • A wiring hub and patch panel may be mounted to a
    wall with a hinged wall bracket, or with a
    distribution rack
  • Hinged wall bracket - 48 cm for the panel to
    swing out from the wall.
  • Distribution rack - minimum 15.2 cm of wall
    clearance for the equipment, plus another
    30.5-45.5 cm for physical access by workmen and
    repairmen. A 55.9 cm floor plate, used to mount
    the distribution rack, will provide stability,
  • If the patch panel, hub and other equipment are
    mounted in a full equipment cabinet, they require
    at least 76.2 cm of clearance in front, in order
    for the door to swing open. Typically, such
    equipment cabinets are 1.8 m high x .74 m wide x
    .66 m deep.

16
Cable access and support
Within 15.2 cm of the wall
10.2 cm
Any wall/ceiling openings that provide access for
the conduit, or sleeved core, must be sealed with
smoke and flame-retardant materials that meet all
applicable codes
17
Identifying Potential Wiring Closets
  • Draw a floor plan of the building to scale, and
    identify all of the devices that will be
    connected to the network. See pg. 290 (MUST DO
    THIS FIRST!)
  • Identify secure locations that are close to the
    POP, that can serve as either the sole wiring
    closet, or as the MDF
  • If IDFs are required. 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 that represent a
    radius of 50 m. from each of the potential hub
    locations.
  • Are there any potential hub locations whose
    catchment areas substantially overlap? If so, you
    could probably eliminate one of the hub
    locations.
  • Are there any potential hub locations whose
    catchment areas can contain all of the devices
    that are to be connected to the network? If so,
    then one of them could probably serve as the
    wiring closet for the entire building
  • If you will need more than one hub in order to
    provide adequate coverage for all of the devices
    that will be connected to the network, check to
    see if one of them is closer to the POP than the
    other(s)? If so, you will probably want to select
    it to serve as the MDF.

18
Wiring closet Floor plan
19
Wiring closet Potential Locations
20
Wiring Closets
  • If there are any potential wiring closet whose
    catchment areas substantially overlap, you could
    probably eliminate one of the wiring closet.
  • If there are any potential wiring closet whose
    catchment areas can contain all of the devices
    that are to be connected to the network, then one
    of them could serve as the wiring closet for the
    entire network.

21
Wiring closet Practice
  • Do any of the circles overlap?
  • Can any of the Potential locations be
    eliminated?
  • Do any of the circles provide coverage for all of
    the devices that will be connected to the
    network?
  • Which of the Potential locations seems to be the
    best?
  • Are there any circles where only a few of the
    devices fall outside the catchment area?
  • Which Potential location is closest to the POP?
  • Based on your findings, list the three best
    possible locations for wiring closets.
  • Based on your findings, how many wiring closets
    do you believe will be required for this network?
  • What are the advantages and disadvantages of each
    of the Potential locations?

22
Wiring closet Practice (cont.)
23
Backbone cabling consists of the following
  • backbone cabling runs
  • intermediate and main cross-connects
  • mechanical terminations
  • patch cords used for backbone-to-backbone
    cross-connections
  • 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

24
Networking Media for Backbone Cabling
  • 100 W UTP (four-pair)
  • Be careful, copper can act as a conductor and
    provide a path for lightening of used outside of
    the building
  • 150 W STP-A (two-pair)
  • 62.5/125 µ optical fiber
  • Optical fiber is preferred because its made of
    glass which is an insulator, not a conductor
  • Single-mode optical fiber

25
Locating an MDF in a Multi-Story Building
26
Locating an MDF in a Multi-Building Campus
27
Backbone TIA/EIA-568-A
  • Each IDF can be connected directly to the main
    distribution facility.
  • IDF horizontal cross-connect (HCC).
  • MDF main cross-connect (MCC).
  • 1st IDF interconnected to a 2nd IDF. The 2nd IDF
    is then connected to the MDF.
  • 2nd IDF intermediate cross-connect (ICC).
  • No more than one ICC can be passed through to
    reach the MCC.

28
Horizontal and Backbone Cabling (Type A)
MDF
IDF
3000m
29
Horizontal and Backbone Cabling (Type B)
2500m
500m
30
Horizontal and Backbone Cabling
31
(No Transcript)
32
ELECTRICITY AND GROUNDING
33
AC vs. DC
  • AC
  • Alternating Current
  • Can present significant problems for a network
  • Adds unwanted voltage to desired signals
  • Inconsistent voltage flow (rises and falls)
  • DC
  • Has constant voltage flow

34
Electrostatic discharge (ESD)
  • Static electricity.
  • The most damaging and uncontrollable form of
    electricity.
  • ESD must be dealt with in order to protect
    sensitive electronic equipment.
  • ESDs can destroy semiconductors and data
  • A solution that can help solve problems that
    arise from ESD is good grounding.

35
Safety grounding
  • Third connector (round) in power socket is called
    the safety ground connection.
  • The safety ground wire is connected to any
    exposed metal part of equipments.
  • The motherboards and computing circuits in
    computing equipment are electrically connected to
    the chassis, this also connects them to the
    safety grounding wire.

36
Purpose of safety grounding
  • Prevent such metal parts from becoming energized
    with a hazardous voltage resulting from a wiring
    fault inside the device.
  • Be used to dissipate static electricity.
  • Whenever an electrical current is passed through
    this path into the ground, it causes protective
    devices such as circuit breakers to activate.

37
Safety Ground Connections
  • Large buildings frequently require more than one
    earth ground.
  • Separate earth grounds for each building are
    required in multi-building campuses.
  • When ground wires in separate locations have
    slightly different potential (voltage), to the
    common and hot wires, they can present a serious
    problem.
  • This errant potential voltage would have the
    ability to severely damage delicate computer
    memory chips.

38
Network devices on separate building
39
Dangerous circuit
  • Due to the ground wires for the devices in one
    location having a slightly different potential to
    both the common and hotwires than the ground
    wires for the devices in the second location.
  • Anyone touching the chassis of a device on the
    network would receive a nasty shock.
  • A good way to avoid having current pass through
    the body, and through the heart, is to use the
    one hand rule.

40
Avoiding dangerous circuit
  • TIA/EIA-568-A specifications for backbone cabling
    permit the use of fiber optic cable, as well as
    UTP cable.
  • UTP could provide a path for potentially fatal
    voltages.
  • When multiple buildings are to be networked, it
    is highly desirable to use fiber-optic cable as
    the backbone.
  • Whenever copper is used for backbone cabling, it
    can provide a pathway for lighting strikes to
    enter a building.

41
NETWORK POWER SUPPLY
42
Normal mode vs common mode
  • Normal mode problems
  • exist between the hot and neutral wires
  • do not, ordinarily, pose a hazard to you or to
    your computer. usually intercepted by a
    computer's power supply, an uninterruptible power
    supply, or an AC power line filter.
  • Common mode problems
  • exist between hot or neutral and the ground
    wires,
  • can go directly to a computer's chassis without
    an intervening filter.
  • do more damage to data signals than normal mode
    problems.
  • harder to detect.

43
Power problem
44
Typical Power Problems
  • Surge
  • Voltage increase gt 110
  • Hubs are especially vulnerable
  • Caused by lightening strikes, the power company,
    or equipment that cycles (AC, elevators, etc.)
  • Responsible for nearly ALL hardware damage
  • Sag/Brownout
  • Sag is a brownout that lasts less than 1 second
  • Voltage falls below 80
  • Account for large portion of power problems

45
Typical Power Problems
  • Spike
  • Overload of voltage
  • Lasts between .5 and 100 microseconds
  • Power line has been struck with a hit of at least
    240V (100 increase)
  • Caused by lightening, power company, equipment
    that cycles (AC, elevators, etc.)
  • Oscillations/Noise (Harmonics)
  • Caused by an excessively long wiring run where
    the wire acts as an antenna.

46
Surge protector pg. 327-328
  • To protect the system equipment from surges
    introduced between the building entrance and the
    system equipment, install the inline surge
    protector between those two points and as close
    as possible to the equipment being protected.
  • To protect the system equipment from surges
    introduced between the system equipment and the
    work area, install the inline surge protector
    between those two points and as close as possible
    to the equipment being protected.
  • To protect the work area equipment that is
    connected to the Local Exchange Carrier (LEC),
    Campus Backbone Cabling or System Equipment. If
    the work area equipment operates over more than
    one-pair, install the inline surge protector as
    close as possible to the equipment being
    protected.

47
Surge suppressor
  • Prevent surges and spikes from damaging the
    networking device.
  • A device called a metal oxide varistor (MOV) is
    most often used as this type of surge suppressor.
  • Can hold up to 330 V
  • Protects the networking devices by redirecting
    excess voltages, that occur during spikes and
    surges, to a ground.
  • Has a limited lifetime.
  • Would not be the best choice for your network.

48
Uninterruptible Power Supply
  • An uninterruptible power source is designed to
    handle only short-duration power outages.
  • Best handles sags and brownouts
  • 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.

49
UPS Components
50
UPS Types
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