Ethernet Cables

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Ethernet Cables
R
R
Sw
Straight-Through
Cross-Over
PC
PC
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Twisted-Pair Cabling

• Common traits of all twisted-pair cabling types
  and categories
• The wires are copper
• The wires come in pairs
• The pairs of wires are twisted around each other
• The pairs of wires are usually enclosed in a
  cable sheath individually and as a group of wires

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Twisted-Pair Cabling

• Crosstalk
• Signal bleed from one cable to another
• Usually occurs in poorly wired media
• Cancellation
• Insulates the signal from the effects of signal
  bleeding

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Unshielded Twisted-Pair (UTP)

• Cabling used for a variety of electronic
  communications

CAT 5e Designed to correct shortcomings of CAT
5, particularly for Gigabit Ethernet and
full-duplex operation. Signaling rate 100MHz
like CAT 5. CAT 6 Recommended cabling for
Ethernet over copper at speeds up to 1 Gigabit.
Signaling rate up to 200MHz.
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Unshielded Twisted-Pair (UTP)

• UTP advantages
• Thin flexible cable that is easy to string
  between walls
• Most modern buildings come with CAT 5e or CAT 6
  UTP already wired into the wall outlets or at
  least run between the floors
• Because UTP is small, it does not quickly fill up
  wiring ducts
• Costs less per foot than other type of LAN cable

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Unshielded Twisted-Pair (UTP)

• UTP disadvantages
• Somewhat susceptible to interference
• Pair twisting does help, but it does not make the
  cable impervious to electrical noise
• Its unrepeated length limit is 100 meters

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RJ-45 Connectors

• Registered Jacks (RJ)
• Type of telecommunication connector used for
  twisted-pair cabling
• Typically RJ-45 connectors resemble the typical
  RJ-11 connectors that connect the phone to the
  wall
• Difference between RJ-45 connectors and RJ-11
  connectors is that the former has eight wires
  (four-pair) and the latter four (two-pair)
• Some RJ-11 connectors are used with three-pair
  (six-wire) UTP

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Terminology

• The RJ-45 jack is the receptacle
• And the RJ-45 plug is the connector at the end of
  the patch cable

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Horizontal Cabling Standards

• Horizontal cabling
• The twisted-pair or fiber-optic media connecting
  workstations and wiring closets
• Electronics Industries Alliance and
  Telecommunications Industry Association (EIA/TIA)
• Define a set of specifications which covers
  outlets near the workstation, mechanical
  terminations in wiring closets, and all cable
  running along the horizontal path between wiring
  closet and workstation (EIA/TIA 568A cabling
  standards, EIA/TIA 569 pathways and spaces)

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Horizontal Cabling Standards
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Horizontal Cabling Standards

• EIA/TIA-568A
• Specifies that the maximum distance for a UTP
  horizontal cable run is 90 meters (295 feet)
• Total of 10 meters is allowed for patch cables
  (a.k.a. patch cords)
• In addition to UTP, the following cable types may
  be used for horizontal pathways
• STP Shielded Twisted Pair
• Fiber-optic

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Wiring Closets

• Contain the wiring and wiring equipment for
  connecting network devices, such as routers,
  switches, patch panels, and hubs
• EIA/TIA-568 and EIA/TIA-569 standards apply to
  the physical layout of media and wiring closets,
  with the latter stating there must be a minimum
  of one wiring closet per floor
• Furthermore, when a given floor area (catchment
  area) exceeds 1,000 square meters, or the
  horizontal cabling more than 90 meters,
  additional wiring closets are needed

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Wiring Closets

• The main distribution facility (MDF) is the
  central junction point for wiring of a star
  topology
• The additional closets are called intermediate
  distribution facilities (IDFs)
• IDFs are required when
• Catchment area of MDF is not large enough to
  capture all nodes
• The LAN is in a multistory facility
• The LAN encompasses multiple buildings

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Proximity to the POP

• Ensure that main wiring closet is close to the
  point of presence (POP) to a wider network, e.g.,
  to the Internet.

Network spanning multiple buildings
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Proximity to the POP
Network spanning multiple floors
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Backbone

• Backbone cable (sometimes called vertical
  cabling) connects wiring closets to each other in
  an extended star topology
• EIA/TIA-568A specifies four different options for
  backbone cabling
• 100-ohm UTP
• 150-ohm STP
• 62.5/125-micron optical fiber (multi-mode)
• Single-mode optical fiber

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Installing Connectors
RJ-45 connector
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Installing Connectors
UTP wires
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Installing Connectors
Jack wiring (T568B)
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Installing Connectors

• EIA/TIA-T568B
• Wiring method used to indicate which colors are
  assigned to which pin for UTP cable
• T568A is sometimes used (different color
  termination sequence)
• Punch tool
• Used to punch down cable at the patch panel or
  wall plate
• Crimp tool
• Used to terminate RJ-45 plug on cable

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Patch Panel
Patch panel (back) pins
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Patch Panel Punch Tool
Patch panel ports
Punch tool used to terminate horizontal cable at
back of patch panel
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Crimp Tool
Used to attach plug to patch cable
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Color Scheme

• Association of pair number with color
• Originally used by the telephone industry
• Pair 1 - White with blue strips (W-Bl)
• Blue with white strips (Bl)
• Pair 2 - White with orange strips (W-O)
• Orange with white strips (O)
• Pair 3 - White with green strips (W-G)
• Green with white strips (G)
• Pair 4 - White with brown strips (W-Br)
• Brown with white strips (Br)

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Termination Sequence

• EIA/TIA
• T568B termination standard
• Most widely used for data communication
• Defines the order in which incoming pairs are
  terminated into plug pins

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T568B Standard

• Each end wired the same, i.e., straight through
• Plug receptacle end with locking tab at bottom
• Yellow pairs/pins used for 10BaseT 100BaseT

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Cross-Over Cable

• Also called an uplink cable
• Cross transmit and receive at one end
• That is, use T568A at one end T568B at other

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Cross-Over Cable
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Straight-Through Cross-Over
Standard Cross-Over
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Pin Numbers
Locking tab on back
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Making Patch Cable

• Cut a about 1½ to 2 of cable off the roll, or
  cut the plugs off an old cable.
• Cut about 2 of the jacket from the end.
• Cut away the ripcord and discard it.
• Untwist the pairs and arrange them in the T568B
  color sequence.
• Cut all eight wires squarely ½
• from the jacket with the wire
• cutter.

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Making Patch Cable
All the way to end

• Insert wires into the plug and push them all the
  way to the end.
• Insert the plug into the crimping tool. Press
  the handles together firmly. Remove plug from
  tool.

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Making Patch Cable

• Inspect plug to be sure the termination is
  correct
• Conductors should all be touching the end of the
  plug.
• All 8 pins should be fully depressed.
• The pins feet should be fully inserted into the
  wire.
• The flange should be fully
• depressed against the jacket,
• and the end of the jacket should
• be beyond the flange.

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Cable Testers Wire Map

• Important measurement a cable tester makes to
  check wiring sequence

Wire map error detection
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Cable Testers Wire Map
Crossed pairs
Split pairs
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Cable Testers Attenuation

• Attenuation is the loss of signal power over the
  distance of a cable
• Signal injector
• Puts traffic on a wire so that a cable tester can
  measure attenuation and crosstalk
• The lower the attenuation, the better

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Cable Testers Noise

• Alternating current (AC) signal noises are called
  oscillations and can alter the digital signals
  that computers receive on the wire
• The motherboard and other internal integrated
  circuits of a computer use the chassis as their
  ground
• Faulty AC wiring can also cause problems with
  transmissions because the signal reference ground
  is the computer chassis and grounding plate

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Cable Testers NEXT

• Near end crosstalk (NEXT)
• Measure of interference from other wire pairs
• Causes of NEXT include
• Split pairs
• Too much wire untwisted at the patch panel, jack,
  or connectors
• Bends, kinks, or stretches in the cabling

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Cable Testers NEXT
NEXT test on a cable analyzer
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Cable Testers Distance Measure

• EIA/TIA-568A specifies maximum cable lengths for
  network media
• Cables that are too long can cause delays in
  transmission and network errors
• Time-domain reflectometer (TDR)
• Cable tester that can detect the overall length
  of a cable or the distance to a cable break

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Three-Layer Network Model

• Divides a network into three connectivity layers
• Consists of
• Core layer
• WAN technology to interconnect sites
• Forms the higher-level backbone
• Distribution layer
• Backbone network used to interconnect buildings
• Forms the campus network
• Access layer
• LAN or group of LANs providing connectivity for
  end-stations (servers, workstations, printers)
• Technology closest to users

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Three-Layer Network Model
Three-layer hierarchical network model
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Two One-Layer Network Models

• Two-layer network model
• Divides a network into two connectivity layers
• Core
• Access
• One-layer network model
• Smaller networks
• Includes WAN connectivity equipment and LAN
  connectivity equipment in same layer
• May be adapted to the two-layer and three-layer
  design models in the future
• Note that the difference between the three models
  is the number of levels of routers

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Two-Layer Network Model
Two-layer hierarchical network model
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One-Layer Network Model
One-layer network model
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Summary

• UTP cabling
• Nomenclature EIA/TIA, wiring closet, MDF, IDF,
  POP, horizontal cable, vertical (backbone) cable
• Installing connectors
• Cable testers
• Network hierarchy models

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End