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Computer Networks

Computer Networks. 6.829 Fall 2005 September 8, 2005 nms.csail.mit.edu/6.829. Muscle-Powered Communications. Human messengers on foot or horseback “Command and Control” between capital and the field 14 AD: Roman relays—50 miles per day for regular mail, 100 miles per day for express mail

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Computer Networks

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  1. Computer Networks 6.829 Fall 2005 September 8, 2005 nms.csail.mit.edu/6.829

  2. Muscle-Powered Communications • Human messengers on foot or horseback • “Command and Control” between capital and the field • 14 AD: Roman relays—50 miles per day for regular mail, 100 miles per day for express mail • 1280 AD: Kublai Khan—200-250 mi per day“Poste Haste”— “Fast Post” —riders signal by horns

  3. “Let us turn now to the system of post-horses by which the Great Khan sends his dispatches. You must know that the city of Khan-balik is a centre from which many roads radiate to many provinces, one to each, and every road bears the name of the province to which it runs. ... When one of the Great Khan's messengers sets out along any of these roads, he has only to go twenty-five miles and there he finds a posting station, which in their language is called yamb and in our language may be rendered as 'horse post'. … Here the messengers find no less that 400 horses, stationed here by the Great Khan's orders and always kept in readiness for his messengers … "By this means the Great Khan's messengers travel throughout his dominions and have lodgings and horses fully accoutred for every stage. … The whole organization is so stupendous and so costly that it baffles speech and writing.” -- Marco Polo (1290)

  4. The Pony Express 1861 AD: The Pony Express • 150-200 mi/day, 1966 mi from Missouri to California, 10-13 days • Longest ride: 14 year old “Buffalo Bill” Cody, 384 mi • Record time: 7 days 17 hours with President Lincoln’s Inaugural Address, March 4, 1861 Western Union’s line puts it out of business, October 1861

  5. Visual communications: The optical telegraph Pics: Proc. Symp. on the Optical Telegraph, Stockholm, June ’94 • Chappe (1763-1805), a “defense contractor”; 1st message successfully sent in 1794 • 1799: Napoleon seizes power; sends “Paris is quiet, and the good citizens are content.” • 1814: Extends from Paris to Belgium & Italy • 1840: 4000 miles, 556 stations, 8 main lines, 11 sublines, each hop ~10 km • Many “advanced” techniques: switching, framing, codes, redundant relays, message acks, priority messages, error notification, primitive encryption!

  6. Scientific Advances • Late 18th—Early 19th Century • Increasing evidence of the close relationship between electricity and magnetism • Oersted (Copenhagen): demonstrated electricity’s ability to deflect a needle • Sturgeon (London), 1825: electromagnet demo • Joseph Henry, 1830: 1-mile demo: current through long wires, causing bell to ring! • Faraday (London), 1831: EM induction experiments (induction ring), basis for motors

  7. The Electric Telegraph • Cooke and Wheatstone, Railroad Telegraph, 1837 • 14 mi installed by 1838 • 4000 mi by 1852

  8. The Electric Telegraph (Samuel Morse) Morse Code (1835-1837) • 1838: demo’d over 2 miles • 1844: US- sponsored demonstration between Baltimore and Washington DC

  9. Dots and Dashes Span the Globe • 1852: First international telegram • Reuters establishes “Telegraph News Network” • 1858: Cyrus Field lays first transatlantic cable • US President & Queen Victoria exchange telegrams • Line fails in a few months • 1866: New cable & technology developed by William Thompson (Lord Kelvin)

  10. Dots and Dashes Span The Globe • Communications “arms” race in the Imperial Age • No nation could trust its messages to a foreign power • 1893: British-owned Eastern Telegraph Company and the French crisis in Southeast Asia • 1914: British cut the German overseas cables within hours of the start of WW I; Germany retaliates by cutting England’s Baltic cables and the overland lines to the Middle East through Turkey • Strategic necessity: circumventing the tyranny of the telegraph lines owned by nation states

  11. Wireless! James Clerk Maxwell (1831-1879) "... we have strong reason to conclude that light itself -- including radiant heat, and other radiations if any -- is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws." Dynamical Theory of the Electromagnetic Field, 1864. Heinrich Hertz (1857 - 1894) • Mid-1880s: Demonstrated experimentally the wave character of electrical transmission in space

  12. Wireless Telegraphy Guglielmo Marconi • 1895: 21 year-old demonstrates communication at distances much greater than thought possible • Offers invention to Italian government, but they refuse • 1897: Demonstrates system on Salisbury Plain to British Royal Navy, who becomes an early customer • 1901: First wireless transmission across the Atlantic • 1907: Regular commercial service commenced

  13. “Portable” radio, circa 1915 Airborne radio telephone, post WW I Wireless in Warfare

  14. The Telegraph Learns to Talk • Morse telegraph: no multiplexing • Only one message sent/received at a time • Second half of 19th century: many researchers work on improving capacity • One idea: sending messages at different pitches (Graham Bell)

  15. The Telephone Alexander Graham Bell • 1876: Demonstrates the telephone at US Centenary Exhibition in Philadelphia • Bell and Elisha Gray rush patents to USPTO, Bell first by a few hours • Bell offers to sell patents to Western Union for $100,000, who refuse. Bell Telephone Company founded 9 July 1877. • 1878: Western Union competes using rival system designed by Thomas Edison and Elisha Gray. Bell sues and wins.

  16. Bell’s Early Telephones + “Most Valuable Patent” US Patent 174,465 (March 7, 1876)

  17. Mechanical Telephone Switch Almon Brown Strowger (1839 - 1902) • 1889: Invents the “girl-less, cuss-less” telephone system

  18. “Ma Bell” and the telcos. • Bell’s patents expire in 1890s; over 6000 independent operators spring up • 1910: Bell System controls 50% of local telephone market • 1913: AT&T & U. S. government reach Kingsbury Agreement: AT&T becomes regulated monopoly while promising "universal" telephone service; Controls “toll” services in U.S. • Long distance interconnection withheld as a competitive weapon • 1950: Bell System controls 84% of the local telephone access market • 1984: Divesture of Ma Bell (Judge Greene) • 1996: Trivesiture of AT&T Bell (AT&T, Lucent, NCR) • Much activitity, mergers, splits, acquisitions over past 10 years

  19. Computer Comms & Packet Switching ARPA: 1957, in response to Sputnik Paul Baran • Early 1960s: New approaches for survivable comms systems; “hot potato routing” and decentralized architecture, 1964 paper Donald Davies, early 1960s • Coins the term “packet” Len Kleinrock (MIT thesis): “Information flow in large communication nets”, 1961 J. Licklider & W. Clark (MIT), On-line Man Computer Communication L. Roberts (MIT), first ARPANET plan for time-sharing remote computers, SOSP ‘67 paper

  20. ARPANET & Internetworking ARPANet • 1967: Connect computers at key research sites across the US using pt-to-pt telephone lines • Interface Message Processors (IMP) ARPA contract to BBN • Ted Kennedy telegram on BBN getting contract BBN team that implemented the interface message processor

  21. ARPANET Topology in 1969 First inter-site demo, 1969. First crash very soon after!

  22. History, contd. • 1970, ARPANET hosts start using NCP; first two cross-country lines (BBN-UCLA and MIT-Utah)

  23. History, contd. • 1972, modified ARPANET email program (BBN), various demos and apps; CYCLADES effort in France; telnet spec • 1973, APRANET becomes international • 1973-75, internetworking effort (Kahn & Cerf, et al.) • 1976, UUCP distributed by AT&T • 1978, TCP and IP split (end-to-end principle) • 1980, ARPANET grinds to halt due to a virus

  24. History, contd. • 1981, many networks (BITNET, CSNET, Minitel, …) • 1982, DoD standardizes on TCP/IP • 1984, DNS introduced • 1986, NSFNet started, NNTP, MX records, big outage in New England • Congestion collapse episodes, Van Jacobson’s solutions • Decentralized administration

  25. Some Decentralized Administration (1987)

  26. History, cont. • 1990, No more ARPANET • 1991, WWW (Berners-Lee) • 1990s: everyone gets on the web • mid-1990s: NSFNet gets out of centralized backbone; ISPs take off • 1996, telcos ask for IP phones to be banned, bubble starts • 2001, bubble bursts; much progress in between! • 2000s: net truly international; more non-PC devices than computers on the Internet

  27. Year 2000

  28. Internet hosts (names) with time:~40% per year

  29. The Big Challenges • Internetworking: interconnecting in the face of • Heterogeneity • Scale • Generality of uses • Sharing • Wireless and mobility • Handling and facilitating evolution: expanding the net toward new uses • Coping with abuses

  30. Highest Link Capacity 2x / 7 months # Internet hosts 2x / 13.3 months Aggregate Internet Traffic 2x / 12 months Bits/s per dollar 2x / 79 months (crude estimate) DRAM Access Time 1.1x / 18months Speed of light 0x / 18 months! d(technology)/dt for networks 1,000,000 100,000 10,000 Normalized Growth since 1980 1,000 Moore’s Law 2x / 18 months 100 10 1 1980 1983 1986 1989 1992 1995 1998 2001 Thanks to Nick Mckeown @ Stanford for some of these data points

  31. Acknowledgments • Professor Randy Katz, UC Berkeley, for several of these slides • Professor Nick McKeown, Stanford, for some data (tech trends) • Various Web sites, including about.com, zakon.org, isc.org

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