Transcript Wire Media: UTP

Wire Media: UTP
• Unshielded Twisted Pair (UTP)
– Ordinary copper wire
– Twisted several times per inch to reduce interference
– Pair of wires needed for a complete electrical signal
– Unshielded: nothing but plastic coating
• No protection from interference
Wire Media: UTP
• Unshielded Twisted Pair (UTP)
– Business telephone wiring traditionally comes
in 4-pair UTP wire bundles
– Used in LAN wiring to use existing building
wiring technology
Wire Propagation: RJ-45
• RJ-45 connector terminates a UTP bundle
– Slightly wider than RJ-11 residential connector
– Width needed for 8 wires
Wire Media: UTP to the Desktop
• UTP
– Dominant for line from desktop to first hub or switch
– Inexpensive to buy and install
– Rugged: can take punishment of office work
– Easily 100 Mbps, 1 Gbps with careful insulation
UTP
First Hub or Switch
Wire Media: Optical Fiber
• Optical Fiber
–
–
–
–
Glass core, surrounding glass cladding
Light source turned on/off for 1/0
Total internal reflection at boundary
Almost no attenuation
Cladding
Core
Light
Source
Reflection
Wire Media: Optical Fiber
• Limited by Distortion
– Light entering at different angles travels
different distances (different number of
reflections)
– Called different modes
– Light from successive bits becomes mixed over
long distances
Light
Source
Wire Media: Optical Fiber
• Multimode Fiber
Mod B
– Wide core makes easy to splice (50 or 62
microns)
– Many angles for rays (modes)
– Short propagation distance (usually 200 m to
500 m)
Light
Source
Wire Media: Optical Fiber
• Single Mode Fiber
– Narrow core difficult to splice (5 or 8 microns)
– Only one angle for rays (one mode), so (almost)
no distortion
– Longer propagation distance (usually up to 2
km for LAN fiber, longer for long-distance
fiber)
– Narrow core makes fiber fragile and difficult to
splice
Wire Media: Optical Fiber
• Optical Fiber
– High speeds over long distances
• 200 m to 2 km
– Costs more than UTP, but worth it on long runs
– Good for all links between hubs and switches
within and between buildings in a site network
Optical
Fiber
Wire Media: UTP and Optical Fiber
• The emerging pattern: UTP from first hub
or switch to desk, Fiber everywhere else on
site
Wire Media: Coax
• Coaxial Cable
– Used in cable TV, VCRs
– Central wire, external concentric cylinder
– Outer conductor wrapped in PVC
Outer Conductor Wrapped in PVC
Inner
Wire
Screw-On Connector
Wire Media: Coaxial Cable
• Coaxial Cable
– Installed widely today in old 10 Mbps Ethernet
LANs
– Not being used in new installations
• Optical fiber more cost-effective for long links
• UTP more cost-effective for desktop links