Guide to Network Cabling Fundamentals

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Guide to Network Cabling Fundamentals

• Chapter 8

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Chapter 8 - Testing and Troubleshooting

• Understand the necessity for testing your cable
  system
• Define and perform tests on copper and fiber
• Understand troubleshooting methods and general
  techniques
• Identify and use testing and troubleshooting
  tools
• Design a disaster avoidance plan
• Manage your documentation

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Testing Your Cabling System

• After the cabling is in place, a final critical
  step remains in the installation testing the
  system
• Three types of cable testing exist
• Operational testing ensures that a system is
  working properly and includes these procedures
  checking all cables for continuity performing
  polarity tests of cable pairs running a
  connectivity test testing for cable shorts and
  opens
• Performance testing is designed to ensure that a
  system complies with all applicable codes and
  standards

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Testing Your Cabling System

• Three types of cable testing (cont.)
• Acceptance testing is designed to demonstrate
  functionality, prove conformity to
  specifications, and ensure performance based on
  customers measurement criteria, called
  parameters
• Acceptance testing serves to satisfy the contract
  with the customer and these requirements the
  types of cable to use for each portion of the
  installation the acceptable means for running
  the cable various types of termination
  equipment the performance expected from each
  type of cable complete documentation of the
  installation and test results

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Testing Copper and Fiber Media

• Test copper UTP cable in accordance with the TIA
  TSB-67 standard, which specifies methods,
  parameters, and minimum requirements for testing
  installed Category 3, 4, and 5 cabling
• There are several benefits of testing and
  certifying according to TSB-67
• Verifying that no faults occurred during the
  installation, and ensure that the system will
  perform according to the users requirements
• Protecting the installer from blame if a problem
  occurs

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Testing Copper and Fiber Media

• TSB-67 defines two types of tests for UTP
• The basic link is the permanent part of a cable
  run that includes 90 meters of horizontal cable,
  the telecommunications outlet, and the first
  punch-down in the telecommunications room
• The channel encompasses the basic link plus all
  patch cords and equipment cords
• These tests should both be performed they are
  important in verifying proper workmanship, and
  they provide a future reference for the systems
  proper state of operation or performance (or
  baseline)

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Testing Copper and Fiber Media

• TSB-67 tests for copper UTP cable
• The wire map test identifies wiring errors (opens
  and shorts, crossed-pair, reversed-pair,
  split-pair), and checks connectivity
• The length test verifies that cable length is
  within the specifications for maximum allowable
  length
• The attenuation test measure a cables signal
  loss from end to end all cable pairs must be
  tested
• The near-end crosstalk (NEXT) test measures the
  signal coupling from one pair of wires to another
  pair within the same cable

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Testing Copper and Fiber Media

• Proposed new tests for copper UTP cable are known
  as TSB-95
• Propagation delay measures the time, in
  nano-seconds (nS), it takes a signal to travel a
  cable
• Attenuation-to-crosstalk ratio (ACR) is the
  difference between the NEXT and attenuation
  measurements
• The power sum measurement compares the crosstalk
  effects on all pairs in a cable
• Return loss is a measurement of the signal that
  echoes or reflects back into the transmitter

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Testing Copper and Fiber Media

• General testing rules for copper UTP cable
• Do not move any cable or equipment during testing
• Record pass/fail indications and always record
  the actual measured values and the date
• If any part of the system is reconfigured, retest
  it
• Always perform the NEXT test and record the
  measurements from both ends of the cable
• When performing channel tests, always test with
  the end-user cords and patch cords in place
• If a cable barely passes a test, record this
  marginal result in the report of actual test
  measurements

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Testing Copper and Fiber Media

• Test fiber-optic cable to demonstrate that any
  exhibited loss does not exceed the acceptable
  limits defined by ANSI/EIA/TIA-568-B.3
• Testing ensures that the cabling system
• Meets the customers attenuation specifications
• Provides documentation of baseline readings,
  which are an essential gauge for future
  troubleshooting
• When testing, test the power levels on the
  transmitter and receiver to ensure proper
  operation

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Testing Copper and Fiber Media

• Attenuation testing of fiber is crucial after
  installation because interruptions in the cable
  (splices and connections) provide more
  opportunities for signal loss
• During attenuation testing, measure cables in
  both directions and at both available wavelengths
• A wavelength is the measure of the color of
  light, expressed in nanometers (nm)
• Spare fibers or unterminated fibers do not
  require attenuation testing, but the do need to
  be tested for continuity

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Testing Copper and Fiber Media

• Attenuation testing must be done on every link
  segment of cable
• Link segments consist of cable, connectors, other
  connections, and splices between two fiber-optic
  termination units in the system
• The three basic link segment types are
  horizontal, backbone, and composite
• To compute the acceptable attenuation value for
  any link segment, use this equationacceptable
  link attenuation cable attenuation connector
  attenuation splice attenuation

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Testing Copper and Fiber Media

• Optical connectors, adapters, and cable
  assemblies must comply with the requirements of
  ANSI/EIA/TIA-604-3-1997, FOCIS 3 also test the
  system in accordance with TIA FOTP
• Follow these procedures before testing begins
  read the equipment manufacturers testing
  instructions ensure that all connectors, jumpers
  and adapters are properly cleaned ensure that
  the light source or optical domain reflectometer
  (OTDR) operates within the range of 85030 nm for
  multimode cable and1300 20 nm for single-mode
  cable

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Testing Copper and Fiber Media

• The steps for testing end-to-end attenuation
• Take a reference reading by connecting a test
  jumper from the power meter to the optical source
• Take a check reading by connecting a second
  jumper to the first with an interconnection
  sleeve
• Subtract the reference from the check reading
• If attenuation is acceptable, proceed, otherwise,
  clean connectors and return to step 2
• Take an official attenuation test reading by
  performing an end-to-end attenuation test
• Determine end-to-end attenuation by subtracting
  the reference from the official attenuation test
  reading

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Troubleshooting Methods and General Techniques

• Successful troubleshooters must be logical,
  methodical, and good at problem solving
• Perform the following troubleshooting steps
• Identify the symptoms
• Verify user competency
• Identify the scope of the problem
• Recreate the problem
• Verify the physical integrity of all connections
• Determine if due to recent system changes
• Determine, implement, and test the solution

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Tools for Testing and Troubleshooting

• In many cases, it is more efficient to use a tool
  that can analyze and isolate system problems
• Tools for testing copper cable include
  multimeters test shorts, opens, continuity
  verifications, attenuation measurements, and
  electrical outlets continuity testers test for
  proper wiring mapping, opens, shorts, bad
  terminations and reversed-pairs certified field
  testers test all parameters required by TSB-67
  and TSB-95 time domain reflectometer (TDR) tests
  for line impedance, attenuation, opens, shorts,
  NEXT, cable distances, and connector or
  terminator problems

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Tools for Testing and Troubleshooting

• Tools (cont.)
• Tools for testing fiber-optic cable include
  power meters and optical light sources, which
  measure a cables signal strength and
  attenuation, and the light source can also
  determine leakage at connectors and bends
  optical time domain reflectometers (OTDRs)
  measure a cables length and signal strength
  jumpers connect the power meter and the light
  source interconnection adapters are circuit
  administration points that provide access to a
  circuit and mates connectors

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Disaster Avoidance

• A disaster is an event that prevents a business
  from performing its critical functions
• Disaster avoidance, or disaster prevention, is a
  series of measures designed to prevent, detect,
  or contain potentially calamitous incidents
• The first priority is to prevent disasters, but
  since this is impossible, the next priority is to
  develop procedures that minimize a disasters
  impact
• Proper planning can greatly reduce the trauma of
  rebuilding and repairing systems after a
  disaster, and it can help ensure the rebuilding
  is successful

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Disaster Avoidance

• Disaster planning
• To ensure disaster avoidance plan soundness,
  increase the amount of installed cables in the
  system, select the proper equipment, and think
  through as many what if scenarios as possible
• One of the best and easiest disaster avoidance
  methods is redundancy, which is built into a
  system by adding duplicate parts at any or all
  points
• Another method involves adding diversity to the
  system, using both fiber and copper to ensure
  that service continues through the copper if
  fiber is disabled

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Disaster Avoidance

• Disaster planning (cont.)
• Redundancy and diversity can be planned in
  backbone cables by running more than one and
  installing them along different paths
• Other aspects of network planning and
  installation are also critical to disaster
  avoidance, including grounding, firestopping,
  and physical connectivity
• Create redundancy for important network data and
  applications by mirroring part of the network to
  another building, city, or state

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Managing Your Documentation

• Managing test results
• Test results are a critical part of the
  documentation
• Use the following guidelines to manage test
  results from cable testers document the
  standards used for testing ensure the latest
  software version for the cable tester and record
  that too select a labeling scheme (cable ID)
  that matches the label on the patch panel or
  outlet select the format and media to use for
  test results
• Most newer cable testers come with the ability to
  download test results - do this every day

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Managing Your Documentation

• Data Management Equipment
• An important part of effective management is
  selecting the right tools for the job
• Consider the following equipment label printers
  range from simple models that require manual
  keypad input to models that connect to test tools
  and print labels after each test is performed
  software solutions such as spreadsheets and
  databases help manage test results, and mapping
  software to provide a logical view of the network

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Chapter Summary

• Test your cable installation before activating
  the service to guarantee that the system is
  working properly. Testing also ensures that all
  installed components meet the customers
  performance specifications, as well as codes and
  standards
• Operational testing includes continuity testing,
  verification of polarity, and connectivity
  testing to ensure that there are no shorts or
  opens. Performance testing ensures that the
  system complies with all applicable codes and
  standards. Acceptance testing is designed to
  prove conformity to specifications and ensure
  performance based on the customers measurement
  criteria

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Chapter Summary

• Always test UTP cable systems in accordance with
  the TIA TSB-67 standard, which specifies methods
  and parameters for testing installed Category 3,
  4, and 5 cabling with a hand-help instrument.
  This standard also defines basic link and channel
  test configurations for UTP cable. TSB-67 tests
  that are currently required for Category 5
  certification include wire map tests, length
  tests, attenuation tests, NEXT (near-end
  crosstalk) tests, and propagation delay tests

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Chapter Summary

• You must test fiber-optic cable for attenuation
  to comply with current standards. You should also
  test for attenuation on all link segments,
  connectors, adapters, and cable assemblies
• Even if you only perform new installations, you
  still need to know how to troubleshoot your
  system. A successful troubleshooter is logical,
  methodical, and good at problem solving.
  Troubleshooting steps include identifying
  symptoms, identifying the scope of a problem, and
  recreating the problem

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Chapter Summary

• Many of the tools you use for everyday
  installation and maintenance are the same ones
  you use to test cables or troubleshoot problems
• Disaster avoidance is designed to ensure the
  continuous availability of critical business
  services in case of disaster. Although you cannot
  prevent all disasters, you can minimize their
  effects by planning redundancy and diversity into
  telecommunications systems

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Chapter Summary

• The documentation manual provides important
  information about your network. This information
  can assist you in troubleshooting network
  problems, and it provides an accurate hardware
  and software inventory