CMPE 150 Fall 2005 Lecture 6

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CMPE 150 Fall 2005Lecture 6

• Introduction to Networks and the Internet

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Announcements

• Labs
• 1 slot either M or W 4-6pm.
• Other slot? T or Th 6-8pm?
• First lab is next week.
• TA office hours T 6-7pm and Th 1-2pm in BME 314.

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Last Class

• PHY.
• Analog and digital technology/communication.
• Digitization.
• Sampling period and sampling rate.
• Bit rate.
• Signal and systems.
• Periodic signals.
• Fourier series.
• Bandwidth limitation.
• Channel capacity.

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Today

• PHY (contd).
• T1 demo.

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Guided Transmission Data

• Magnetic Media
• Twisted Pair
• Coaxial Cable
• Fiber Optics

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Magnetic Media

• Examples?
• Advantages?
• Disadvantages?

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Twisted Pair

• Oldest but still very common.
• Telephone system.
• Cheap and effective for long ranges.
• Bundles of twisted pairs.
• Can transmit both analog and digital signals.
• Bandwidth depends on thickness of wire and
  distance traveled.
• Mb/s for few kilometers.

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Twisted Pair

• (a) Category 3 UTP.
• (b) Category 5 UTP.

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Twisted Pair
http//searchnetworking.techtarget.com/sDefinition
/0,,sid7_gci211752,00.html
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Coaxial Cable

• Better performance than twisted pair, i.e.,
  higher bandwidth and longer distances.
• Good noise immunity.
• But
• Bandwidths close to 1GHz.
• Used widely in telephone networks for longer
  distances but gradually being replaced by fiber.
• Used for CATV!

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Coaxial Cable
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Fiber Optics

• Optical transmission.
• Optical transmission system light source,
  medium, and detector.
• Pulse of light 1.
• No light 0.
• Transmission medium ultra thin fiber of glass.
• Detector generates electrical pulse when
  perceives light.

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Transmitting Light

• (a) Three examples of a light ray from inside a
  silica fiber impinging on the air/silica boundary
  at different angles.
• (b) Light trapped by total internal reflection.

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Fiber Cables

• (a) Side view of a single fiber.
• (b) End view of a sheath with three fibers.

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Fiber Optic Networks

• A fiber optic ring.

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Fiber Optic Networks (2)

• A passive star connection in a fiber optics
  network.

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Fiber versus Copper Wire

• Fiber can handle much higher bandwidths.
• Low attenuation 50km without repeater.
• Unaffected by power surges/outages, and
  interference.
• Fiber is thin and lightweight easy to deploy and
  add new capacity.
• Difficult to tap.
• But

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Fiber versus Copper (contd)

• Fiber can be damaged easily.
• Optical transmission is unidirectional, so need 2
  fibers or 2 frequencies for 2-way communication.
• Fiber and fiber interfaces is more expensive.

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Public Switched Telephone System

• Structure of the Telephone System
• The Politics of Telephones
• The Local Loop Modems, ADSL and Wireless
• Trunks and Multiplexing
• Switching

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Structure of the Telephone System

• (a) Fully-interconnected network.
• (b) Centralized switch.
• (c) Two-level hierarchy.

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Structure of the Telephone System (2)

• A typical circuit route for a medium-distance
  call.

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Major Components of the Telephone System

• Local loops
• Connection from subscriber to end office.
• Trunks
• Outgoing lines connecting offices.
• Toll office
• Connects end offices.
• Switching offices
• Where calls are moved from one trunk to another.