Network Cabling

1
Network Cabling

• Unit 25
• Data Communications and Networks

2
Types of network cabling

• In the past co-axial cable was used for LAN
  networks
• Today UTP (unshielded twisted pair) is mostly
  used for office wiring
• In some situations STP (shielded twisted pair)
  may be used.
• Fibre optic cable may be used for the network
  backbone

3
Types of network cabling
RJ45 plug
BNC plug
UTP cable
Co-axial cable
Fibre optic cables
4
Types of LAN
5
10Base5

• The original Ethernet specification created by
  Intel, Xerox and DEC.
• Uses thick coaxial cable (10mm) in a bus topology
• Connects to computer via a transceiver which is
  clamped to the cable

Co-axial cable
Transceiver
Connector to computer
6
10Base2

• An improvement on 10Base5 in that it used thinner
  co-axial cable (RG58 5mm diameter) which was
  cheaper and easier to install
• Topology was still bus but the cable connected to
  each NIC via BNC plugs and a T-piece
• As with 10Base5 a terminator was required at each
  end of the cable to prevent signal bounce

BNC socket on NIC
Terminator
T-piece
BNC plug
7
10Base-T

• Uses UTP (unshielded twisted pair) cable with
  RJ45 connectors
• UTP cable is cheaper than co-axial cable
• Easier to install since the cable is more
  flexible
• Uses a star topology with a hub or switch at the
  centre
• Star topology is more reliable and easier to
  troubleshoot

8
100Base-T

• Same topology and connectors as 10Base-T
• Speed increased to 100Mbps
• Current office LAN standard
• Many LAN NICs and switches are 10/100
  auto-sensing

9
1000Base-T

• Also called Gigabit Ethernet
• Next upgrade from 100Mb LAN
• Uses the same cables and connectors as 100Base-T
• Uses all 4 pairs of wires in UTP cable

10
UTP cable types

• UTP cable is available in various categories

11
UTP cable types

• UTP cable is also available for installation in
• General office space this is usually PVC coated
  cable, which may give off poisonous fumes in a
  fire
• Plenum that is the space between the ceiling
  and the floor above it. Cable located in these
  spaces should be coated in Teflon or rated as
  LSNH (Low Smoke No Halogen) which means they do
  not give off poisonous fumes or smoke in a fire.
• Plenum cables are generally more expensive.

12
STP cable

• Similar to UTP but with a foil shield around the
  wires
• Used in locations where electrical interference
  may be a problem, e.g. factories and air
  conditioning plant

Foil shield
Wire pairs
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Network cable installation
Fibre optic link to server room
Network cabinet
PC
Office
NIC
Switch
Ready made UTP cable
Ready made UTP cable
RJ45 wall socket
Patch panel
Custom made UTP wiring
14
Network cable installation

• The minimum radius through which a UTP cable
  should be bend is 4 times its diameter.
• Always leave some cable slack in case of
  repositioning or repairs
• Use cable ties to keep bunches of cable tidy do
  not over-tighten the ties.
• Always number cables and sockets
• Keep cables clear of fluorescent lights or other
  electrical equipment
• Do not run data cables inside or tie data cable
  to electrical trunking
• Always test each section of the cabling as it is
  completed

15
Network cabling terminology

• EIA/TIA 568A an industry standard for UTP
  wiring. Defines performance characteristics of
  cables and connectors, colour codes for wiring
  schemes etc.
• Crosstalk. This is the way signals from one cable
  can interfere with signals on another adjacent
  cable. The purpose of the twists in UTP wire is
  to reduce the effects of crosstalk
• Attenuation. This is the loss of signal strength
  due to the resistance in the wire. Long cables
  and poorly made connections increase attenuation.