1 / 43

CE80N Introduction to Networks & The Internet

CE80N Introduction to Networks & The Internet. Dr. Chane L. Fullmer UCSC Winter 2002. Reading. Chapter 3, Telephones Everywhere Chapter 4, The World Was Once Analog, Chapter 5, The Once and Future Digital Network; . Telephone Network. Telephone analogy for development of the Internet

presley
Download Presentation

CE80N Introduction to Networks & The Internet

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CE80N Introduction to Networks&The Internet Dr. Chane L. Fullmer UCSC Winter 2002

  2. Reading • Chapter 3, Telephones Everywhere • Chapter 4, The World Was Once Analog, • Chapter 5, The Once and Future Digital Network; CE80N -- Winter 2002 -- Lecture #2

  3. Telephone Network • Telephone analogy for development of the Internet • Getting going (one person with the “only” phone does not gain much) • Early phone development was fragmented: • Each town/locale/region had independent phone system • No hardware standards (especially international) • Connections made manually (human operators) CE80N -- Winter 2002 -- Lecture #2

  4. History of the Telephone • 1876: Alexander Graham Bell obtains patent for the telephone • 1877: The first commercial telephone service, Bell Telephone, is in operation • 1881: The first long-distance line for public use opens between Boston and Providence • 1891: The first automatic dial system is patented • 1900: Loading coil, a device which significantly reduces the tendency of a telephonic signal to grow weaker over distance, is developed CE80N -- Winter 2002 -- Lecture #2

  5. History of the Telephone • 1915: Formal opening of line between New York and San Francisco • 1927: Commercial telephone service by radio between New York and London opens for the first time • 1947: Onset of use of microwave radio, later to become dominant carrier for long-distance telephony in U.S. • 1965: Onset of the use of an electronic switching system with the first commercial electric central office • 1988: Use of first trans-Atlantic fiber-optic cable for telephone CE80N -- Winter 2002 -- Lecture #2

  6. Telephone is pervasive CE80N -- Winter 2002 -- Lecture #2

  7. The Telephone Network • Provides Universal Service • Any individual user may call up any other user. • Ubiquitous CE80N -- Winter 2002 -- Lecture #2

  8. A Necessary Perspective • Today (and for a bit longer?) two network “types”: voice, data. • Both use telephone company (telco) services -- and sometimes other services. • Need to understand basic telco to understand the Internet. CE80N -- Winter 2002 -- Lecture #2

  9. Telephone Network • Interconnects billions of phones world-wide • Designed specifically for voice: • two-way conversations • small end-to-end delays • dedicated circuit is set up between two endpoints • Telephone handset: • carbon microphone, sound pressure changes resistance. (constant voltage). Current becomes “analog” of sound • Earphone turns current into sound pressure (moves diaphragm to move air, create sound pressure) CE80N -- Winter 2002 -- Lecture #2

  10. Plain Old Telephone Service (POTS) Source: Telephony Basics http://jhunix.hcf.jhu.edu/~tnaugler/770.512/Common_files/TelephonyBasics/TelephonyBasics.htm CE80N -- Winter 2002 -- Lecture #2

  11. Local Exchange Carrier • Local Loop – The connection between the central office (CO) and your home. • Local Loop Bypass – Replacing the wired connection from the CO with a wireless link. CE80N -- Winter 2002 -- Lecture #2

  12. Inter-Exchange Carrier CE80N -- Winter 2002 -- Lecture #2

  13. Cellular Network Source: WebProForum http://www.iec.org/tutorials/cell_comm/ CE80N -- Winter 2002 -- Lecture #2

  14. Internet Telephony Source: WebProForum http://www.iec.org/tutorials/int_tele/index.html CE80N -- Winter 2002 -- Lecture #2

  15. CE80N -- Winter 2002 -- Lecture #2

  16. Phone-to-phone conversations CE80N -- Winter 2002 -- Lecture #2

  17. It’s An Analog World

  18. Electromagnetic waves • Frequency = Speed of Light/Wavelength • f (Hz) = 3x108/l(meters) Source: NASA http://imagers.gsfc.nasa.gov/ems/ems.html CE80N -- Winter 2002 -- Lecture #2

  19. EM Spectrum • AM radio (550-1600 kHz) • FM radio (88 – 108 MHz) • TV (52-88 MHz, 174-216 MHz, 470-900 MHz) • Satellite (GHz) • Infrared (200-300 THz) CE80N -- Winter 2002 -- Lecture #2

  20. The Analog World • Analog devices • An analog device maintains an exact physical analog of information. • Phonograph – Physical image (grooves) • Tape recorder/player – Magnetic image • Early telephone handset – mic./speaker • Not Perfect – • Prone to distortion • Hiss, cracks, pops • High/Low end roll-off CE80N -- Winter 2002 -- Lecture #2

  21. Digital and Analog • Digital signals can be any one of a finite number of discrete values • Grades, digital watch, day of the year, letters in the alphabet, integers • Analog signals can be any one of an infinite number of values • Voice signal into a microphone, analog watch, real numbers, electromagnetic wave CE80N -- Winter 2002 -- Lecture #2

  22. Digital versus Analog • Digital generally has better performance • Regenerative repeaters • Analog - distortion and noise cumulative • Digital - true regeneration • Analog simpler (lower cost) • High installed analog base • Cost of digital circuitry now decreasing CE80N -- Winter 2002 -- Lecture #2

  23. Binary Number System • We have 10 fingers • Computers have devices with 2 states ... 1000 100 10 1 ... 10^310^210^110^0 10011 the binary number 2^42^32^22^12^0 place values (1 * 2^4) + (0 * 2^3) + (0 * 2^2) + (1 * 2^1) + (1 * 2^0) = 16 + 0 + 0 + 2 + 1 = 19 CE80N -- Winter 2002 -- Lecture #2

  24. Binary Number System • Text can be represented in binary • ASCII - American Standard Character Information Interchange Ascii Binary CodeA 01000001 a 01100001B 01000010 b 01100010C 01000011 c 01100011D 01000100 d 011001001 00110001 # 001000112 00110010 $ 001001003 00110011 % 00100101 CE80N -- Winter 2002 -- Lecture #2

  25. Sampling – A Moving Snapshot • Recording of voltage levels at prescribed time intervals. • Nyquist’s Theorem: If an analog signal is sampled at 2x(highest frequency), we can adequately reproduce the signal. • Highest frequency in voice is 4000 Hz. Sample at 8000 Hz (disconnect/connect 8000 times per second) • Analogy – movie frames CE80N -- Winter 2002 -- Lecture #2

  26. Quantization • Round up the voltage level to the nearest of 256 predetermined levels • Quantizing error (difference between actual level and level the voltage was rounded to) • AKA lossiness • Low amplitude signals more affected - add more quantizing levels CE80N -- Winter 2002 -- Lecture #2

  27. Quantization • Convert the 256 quantization levels to an 8-bit code • PCM code • Every sound over the telephone is one of 256 unique pitches and volumes. CE80N -- Winter 2002 -- Lecture #2

  28. Sampled Voice • Sample voice signal 8000 times/second • voice signal is bandlimited to 3.4 kHz (filter at 4 kHz) • Quantize samples to 256 quantization levels • logarithmic spacing gives better resolution at the low signal levels • Each sample is represented by 8 bits • Basic rate for voice is 64 Kbps CE80N -- Winter 2002 -- Lecture #2

  29. Sampled Music -- CDs • Sample music signal 44,100 times/second • Music signal is bandlimited to 22 kHz CE80N -- Winter 2002 -- Lecture #2

  30. Days of Future Past • Digital and back again • Smoke signals • Drums • Flashlights • Telegraph • Morse Code (encoding system) CE80N -- Winter 2002 -- Lecture #2

  31. Days of Future Past • Telegraph • Users did not have to deal with the Morse Code directly • Instant communication – (office to office) • The Telephone System began as analog, but has now transformed over time to a digital network. CE80N -- Winter 2002 -- Lecture #2

  32. The Digital Network • The Internet is digital – so are the computers that you use…. • Uses a binary encoding system • Two symbols – 0 or 1 • Again, users do not need to be aware of the encoding system used in the Internet. CE80N -- Winter 2002 -- Lecture #2

  33. Time-Division Multiplexing • Carry many voice conversations on one link • Significant cost savings • One single line instead of 24 separate lines • Example: Freight Transportation • Freight cars (from 5 companies) • 5 separate locomotives, 5 lines • 5 separate trains, 1 line • Join all boxcars together to single engine, single track • Co A + Co B + Co C + Co A + Co B + Co C ... CE80N -- Winter 2002 -- Lecture #2

  34. Time Division Multiplexing • Carry many voice conversations on one link • Example: 24-to-1 multiplexer • Samples 24 voice links 24 times as fast as the input rate • 24 samples constitute a frame • Multiplexed links can be multiplexed further CE80N -- Winter 2002 -- Lecture #2

  35. Digital Signaling (DS) Hierarchy: CE80N -- Winter 2002 -- Lecture #2

  36. Circuit Switching • Network consists of switches • Each user is connected to a switch • To connect two users, a circuit must be established through the network • Switch consists of: • switching hardware => data plane • switch controller => control plane CE80N -- Winter 2002 -- Lecture #2

  37. Signaling • Mechanism to set up and tear down circuits • Performed by switch controllers • Establishment of a telephone call: • handset goes off-hook • user dials numbers • switch controller: • interprets tones and determines destination • sets up a circuit to the remote-end system • rings the remote end-system • remote user picks up phone CE80N -- Winter 2002 -- Lecture #2

  38. Issues in the Telephone Network • Circuit switching: • circuit is limited to 64 kbps • wasteful of bandwidth when the circuit is idle • unsuitable for multimedia services • Infrastructure: • huge investment in existing equipment • demand for new services CE80N -- Winter 2002 -- Lecture #2

  39. Compare and Contrast • Internet • packet-switching • connectionless • dumb network • intelligent end-systems • unreliable connection • designed for data • no quality-of-service • Telephone Network • circuit-switching • connection-oriented • intelligent network • dumb end-systems • reliable connection • designed for voice • quality-of-service • idle time wasted • bandwidth granularity problem CE80N -- Winter 2002 -- Lecture #2

  40. The Digital Network • Summary • The telephone system is pervasive, ubiquitous, and provides universal service. • Digital vs Analog • Sampling and quantization to convert analog signals • The telephone network is now digital too. CE80N -- Winter 2002 -- Lecture #2

  41. Glossary • Analog • Any representation of information in which the amount of a substance or signal is proportional to the information represented • A-to-D converter • Abbreviation for Analog-to-Digital converter. CE80N -- Winter 2002 -- Lecture #2

  42. Glossary • Binary • Any number system that uses two values. • Binary digit (bit) • Either a 0 or 1. • Nibble – 4 bits (half a byte) • Byte -- 8 bits CE80N -- Winter 2002 -- Lecture #2

  43. Glossary • Digital • Any technology that uses numbers to represent information. • Distortion • Input signals that are changed in unintended ways. • Integrated circuit • A small complex electronic device that contains many transistors. CE80N -- Winter 2002 -- Lecture #2

More Related