Physical Media

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Physical Media
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Physical Media

• physical link what lies between transmitter
  receiver
• guided media
• signals propagate in solid media copper, coax,
  fiber
• unguided media
• signals propagate freely, e.g., radio signals

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Common Cabling

• Copper
• Twisted Pair
• Unshielded (UTP)
• CAT-1, CAT-2, CAT-3, CAT-4, CAT-5, CAT-5e
• Shielded (STP)
• Coaxial Cable
• Cable TV cable
• Fiber
• Single-mode
• Multi-mode

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Twisted Pair

• Most common LAN interconnection
• Multiple pairs of twisted wires
• Twisting to eliminate interference
• More twisting Higher bandwidth, cost
• Standards specify twisting, resistance, and
  maximum cable length for use with particular link
  layer

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Twisted Pair

• 5 categories
• Category 1
• Voice only (telephone wire)
• Category 2
• Data to 4Mbs (LocalTalk)
• Category 3
• Data to 10Mbs (Ethernet)
• Category 4
• Data to 20Mbs (16Mbs Token Ring)
• Category 5 (100 MHz)
• Data to 100Mbs (Fast Ethernet)
• Category 5e (350 MHz)
• Data to 1000Mbs (Gigabit Ethernet)

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Twisted Pair

• Common connectors for Twisted Pair
• RJ11 (6 pairs)
• RJ45 (8 pairs)
• Allows both data and phone connections
• (1,2) and (3,6) for data, (4,5) for voice
• Crossover cables for NIC-NIC, Hub-Hub connection
  (Data pairs swapped)

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UTP

• Unshielded Twisted Pair
• Limited amount of protection from interference
• Commonly used for voice and Ethernet
• Voice multipair 100-ohm UTP

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STP

• Shielded Twisted Pair
• UTP susceptible to radio and electrical
  interference
• To reduce this interference, extra shielding
  material added to obtain STP
• Cables heavier, bulkier, and more
• Often used in token ring topologies
• 150 ohm STP two pair (IEEE 802.5 Token Ring)
• Not as common as UTP

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Coaxial cable

• Single copper conductor at center
• Plastic insulation layer
• Highly resistant to interference
• Braided metal shield
• Support longer connectivity distances over UTP

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Coaxial cable

• Thick (10Base5)
• Large diameter 50-ohm cable
• N connectors
• Thin (10Base2) cables
• Small diameter 50-ohm cable
• BNC, RJ-58 connector
• Video cable
• 75-ohm cable
• BNC, RJ-59 connector
• Not compatible with RJ-58

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Fiber

• Center core made of glass or plastic fiber
• Transmit light versus electronic signals
• Protects from electronic interference, moisture
• Plastic coating to cushion core
• Kevlar fiber for strength
• Teflon or PVC outer insulating jacket

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Fiber

• Single-mode fiber
• Smaller diameter (12.5 microns)
• One mode only
• Preserves signal better over longer distances
• Typically used for SONET or SDH
• Lasers used to signal
• More expensive
• Multi-mode fiber
• Larger diameter (62.5 microns)
• Multiple modes
• LEDs used to signal
• WDM and DWDM
• Photodiodes at receivers

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PL Fiber connectors

• ESCON
• Duplex SC
• ST
• MT-RJ (multimode)
• Duplex LC

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Wireless

• Entire spectrum of transmission frequency ranges
• Radio
• Infrared
• Lasers
• Cellular telephone
• Microwave
• Satellite
• Acoustic (see ESE sensors)
• Ultra-wide band
• http//www.ntia.doc.gov/osmhome/allochrt.html

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What runs on them?
Protocol Summary
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Summary

• When connecting 2 nodes, you have 2 choices
• Use wires to connect the nodes
• What cable to use to connect the transmitter and
  receiver?
• Twisted Pair
• Coax
• Fiber
• Wireless transmission