Computer Networks

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Computer Networks

• 15-744 Spring 2007
• January 17, 2006
• www.cs.cmu.edu/dga/15-744/S07

2
Logistics

• Target class size 24
• people registered 29
• people on waitlist 29
• So
• Please sign roll sheet today Monday!
• But If youre not a Ph.D. student, odds are not
  good.

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Syllabus and official stuff

• Please see Web page for syllabus
• Check the announcements frequently!
• Course requirements
• Read the papers before class! Participate!
• Four assignments (really, 2 split in ½)
• Two theory
• Two tools of the trade (analysis measurement)
• Two midterm-type exams (mid end)
• And a project in a pear tree

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Project

• Groups of 3
• Regular meetings w/course staff over the semester
• Goal Real, meaningful research
• I expect some of them to lead to pubs
• Challenge Background vs. problem selection
• Get started early run ideas past us!
• First meeting is SOON 02/05

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Paper Discussion Site

• Experiment this year On-line slashdot-style
  paper discussion
• Ask the Authors Top-ranked questions about
  contemporary papers will be forwarded to the
  authors
• Collaborative with 15-849 and a networks class at
  Georgia Tech
• See website for link to the site
• Create accounts soon.

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Background

• A standard undergrad networking course of some
  sort.
• IP addressing, some simple routing (RIP,
  link-state), some Ethernet and CSMA/CD,
  understand bandwidthdelay products, latency, a
  bit of TCP
• http//www.cs.cmu.edu/srini/15-441/F06/

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Questions about logistics?

• Or should we move on to networking?
• In a manner of speaking

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Muscle-Powered Communications

• Human messengers on foot or horseback
• Command and Control between capital and the
  field
• 14 AD Roman relays50 miles per day for regular
  mail, 100 miles per day for express mail
• 1280 AD Kublai Khan200-250 mi per dayPoste
  Haste Fast Post riders signal by horns

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• 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 than 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)

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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
  Lincolns Inaugural Address, March 4, 1861
• Western Unions line puts it out of business,
  October 1861

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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!

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Scientific Advances

• Late 18thEarly 19th Century
• Increasing evidence of the close relationship
  between electricity and magnetism
• Oersted (Copenhagen) demonstrated electricitys
  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

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The Electric Telegraph

• Cooke and Wheatstone, Railroad Telegraph,
  1837
• 14 mi installed by 1838
• 4000 mi by 1852

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The Electric Telegraph (Samuel Morse)

• Morse Code (1835-1837)
• 1838 demod over 2 miles
• 1844 US- sponsored demonstration between
  Baltimore and Washington DC

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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)

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Dots and Dashes Span The Globe

• Communications arms race in the Imperial Age
• No nation could trust its messages to a foreign
  power
• 1914 British cut the German overseas cables
  within hours of the start of WW I Germany
  retaliates by cutting Englands 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

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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

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Early Uses (cf. IM today!)

• Valentine by a Telegraph Clerk (male) to a
  Telegraph Clerk (female)
• "The tendrils of my soul are twinedWith thine,
  though many a mile apart,And thine in
  close-coiled circuits windAround the needle of
  my heart.
• "Constant as Daniell, strong as
  Grove,Ebullient through its depths like Smee,My
  heart pours forth its tide of love,And all its
  circuits close in thee.
• "O tell me, when along the lineFrom my full
  heart the message flows,What currents are
  induced in thine?One click from thee will end my
  woes."
• Through many an Ohm the Weber flew,And
  clicked this answer back to me, --"I am thy
  Farad, staunch and true,Charged to a Volt with
  love for thee."

Daniell, Grove and Smee are types of batteries
used by telegraphers.
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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

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Wireless in Warfare
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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)

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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.

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Bells Early Telephones Most Valuable Patent
US Patent 174,465 (March 7, 1876)
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Mechanical Telephone Switch

• Almon Brown Strowger (1839 - 1902)
• 1889 Invents the girl-less, cuss-less
  telephone system

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Ma Bell and the telcos.

• Bells patents expire in 1890s over 6000
  independent operators spring up
• 1910 Bell System controls 50 of local telephone
  market
• 1913 ATT U. S. government reach Kingsbury
  Agreement ATT 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 ATT Bell (ATT, Lucent,
  NCR)
• Much activitity, mergers, splits, acquisitions
  over past 10 years

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Computer Comms Packet Switching

• ARPA 1957, in response to Sputnik
• Paul Baran (RAND)
• Early 1960s New approaches for survivable comms
  systems hot potato routing and decentralized
  architecture, 1964 paper
• Donald Davies (UK NPL), early 1960s
• Coins the term packet
• Len Kleinrock (MIT) Information flow in large
  communication nets, 1961
• J. Licklider Galactic Network (MIT and then
  head of computer research at DARPA)
• L. Roberts (MIT), first ARPANET plan for
  time-sharing remote computers, SOSP 67 paper

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

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

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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.)
• 1973, Bob Metcalfes Harvard thesis Ethernet
• 1976, UUCP distributed by ATT
• 1978, TCP and IP split (end-to-end principle)
• 1980, ARPANET grinds to halt due to a virus

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(No Transcript)
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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 Jacobsons
  solutions
• Decentralized administration

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Some Decentralized Administration (1987)
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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

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Year 2000
36
Internet hosts (names) with time40 per year
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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

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d(technology)/dt for networks
1,000,000
100,000
10,000
Normalized Growth since 1980
1,000
Moores Law 2x / 18 months
100
10
1
1980
1983
1986
1989
1992
1995
1998
2001
Thanks to Nick Mckeown _at_ Stanford for some of
these data points
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Acknowledgments

• Professor Hari Balakrishnan, MIT, for many of
  these slides
• 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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For Next Time

• Please read The Design Philosophy of the DARPA
  Internet Protocols