Computer Networks15-744 Spring 2007January 17, 2006

www.cs.cmu.edu/~dga/15-744/S07

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

Syllabus and official stuffPlease see Web page for syllabusCheck the announcements frequently!Course requirementsRead the papers before class! Participate!Four assignments (really, 2 split in )Two theoryTwo tools of the trade (analysis & measurement)Two midterm-type exams (mid & end)And a project in a pear tree

ProjectGroups of 3Regular meetings w/course staff over the semesterGoal: Real, meaningful researchI expect some of them to lead to pubsChallenge: Background vs. problem selectionGet started early; run ideas past us!First meeting is SOON 02/05

Paper Discussion SiteExperiment this year: On-line slashdot-style paper discussionAsk the Authors: Top-ranked questions about contemporary papers will be forwarded to the authorsCollaborative with 15-849 and a networks class at Georgia TechSee website for link to the siteCreate accounts soon.

BackgroundA standard undergrad networking course of some sort.IP addressing, some simple routing (RIP, link-state), some Ethernet and CSMA/CD, understand bandwidth*delay products, latency, a bit of TCPhttp://www.cs.cmu.edu/~srini/15-441/F06/

Questions about logistics?Or should we move on to networking?In a manner of speaking

Muscle-Powered CommunicationsHuman messengers on foot or horsebackCommand and Control between capital and the field14 AD: Roman relays50 miles per day for regular mail, 100 miles per day for express mail1280 AD: Kublai Khan200-250 mi per day Poste Haste Fast Post riders signal by horns

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)

The Pony Express1861 AD: The Pony Express150-200 mi/day, 1966 mi from Missouri to California, 10-13 days Longest ride: 14 year old Buffalo Bill Cody, 384 miRecord time: 7 days 17 hours with President Lincolns Inaugural Address, March 4, 1861

Western Unions line puts it out of business, October 1861

Visual communications: The optical telegraph 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!Pics: Proc. Symp. on the Optical Telegraph,Stockholm, June 94

Scientific AdvancesLate 18thEarly 19th CenturyIncreasing evidence of the close relationship between electricity and magnetismOersted (Copenhagen): demonstrated electricitys ability to deflect a needleSturgeon (London), 1825: electromagnet demoJoseph Henry, 1830: 1-mile demo: current through long wires, causing bell to ring!Faraday (London), 1831: EM induction experiments (induction ring), basis for motors

The Electric TelegraphCooke and Wheatstone, Railroad Telegraph, 1837 14 mi installed by 18384000 mi by 1852

The Electric Telegraph (Samuel Morse)Morse Code (1835-1837)1838: demod over 2 miles1844: US- sponsored demonstration between Baltimore and Washington DC

Dots and Dashes Span the Globe1852: First international telegramReuters establishes Telegraph News Network1858: Cyrus Field lays first transatlantic cableUS President & Queen Victoria exchange telegramsLine fails in a few months1866: New cable & technology developed by William Thompson (Lord Kelvin)

Dots and Dashes Span The GlobeCommunications arms race in the Imperial AgeNo nation could trust its messages to a foreign power1914: 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 TurkeyStrategic necessity: circumventing the tyranny of the telegraph lines owned by nation states

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

Early Uses (cf. IM today!)Valentine by a Telegraph Clerk (male) to a Telegraph Clerk (female): "The tendrils of my soul are twined With thine, though many a mile apart, And thine in close-coiled circuits wind Around 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 line From 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.

Wireless TelegraphyGuglielmo Marconi1895: 21 year-old demonstrates communication at distances much greater than thought possibleOffers invention to Italian government, but they refuse1897: Demonstrates system on Salisbury Plain to British Royal Navy, who becomes an early customer1901: First wireless transmission across the Atlantic1907: Regular commercial service commenced

Wireless in Warfare

The Telegraph Learns to TalkMorse telegraph: no multiplexingOnly 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)

The TelephoneAlexander Graham Bell1876: Demonstrates the telephone at US Centenary Exhibition in Philadelphia Bell and Elisha Gray rush patents to USPTO, Bell first by a few hoursBell 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.

Bells Early Telephones + Most Valuable PatentUS Patent 174,465 (March 7, 1876)

Mechanical Telephone SwitchAlmon Brown Strowger (1839 - 1902)1889: Invents the girl-less, cuss-less telephone system

Ma Bell and the telcos.Bells patents expire in 1890s; over 6000 independent operators spring up1910: Bell System controls 50% of local telephone market1913: 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 weapon1950: Bell System controls 84% of the local telephone access market1984: 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

Computer Comms & Packet SwitchingARPA: 1957, in response to SputnikPaul Baran (RAND)Early 1960s: New approaches for survivable comms systems; hot potato routing and decentralized architecture, 1964 paperDonald Davies (UK NPL), early 1960sCoins the term packetLen Kleinrock (MIT): Information flow in large communication nets, 1961J. 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

ARPANET & InternetworkingARPANet1967: 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 implementedthe interface message processor

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

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

History, contd.1972, modified ARPANET email program (BBN), various demos and apps; CYCLADES effort in France; telnet spec1973, APRANET becomes international1973-75, internetworking effort (Kahn & Cerf, et al.)1973, Bob Metcalfes Harvard thesis: Ethernet1976, UUCP distributed by AT&T1978, TCP and IP split (end-to-end principle)1980, ARPANET grinds to halt due to a virus

History, contd.1981, many networks (BITNET, CSNET, Minitel, )1982, DoD standardizes on TCP/IP1984, DNS introduced1986, NSFNet started, NNTP, MX records, big outage in New EnglandCongestion collapse episodes, Van Jacobsons solutionsDecentralized administration

Some Decentralized Administration (1987)

History, cont.1990, No more ARPANET1991, WWW (Berners-Lee)1990s: everyone gets on the webmid-1990s: NSFNet gets out of centralized backbone; ISPs take off1996, telcos ask for IP phones to be banned, bubble starts2001, bubble bursts; much progress in between!2000s: net truly international; more non-PC devices than computers on the Internet

Year 2000

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

The Big ChallengesInternetworking: interconnecting in the face ofHeterogeneityScaleGenerality of uses

SharingWireless and mobilityHandling and facilitating evolution: expanding the net toward new usesCoping with abuses

d(technology)/dt for networksMoores Law2x / 18 months1101001,00010,000100,0001,000,00019801983198619891992199519982001Normalized Growth since 1980Thanks to Nick Mckeown @ Stanford for some of these data points

AcknowledgmentsProfessor 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

For Next TimePlease read The Design Philosophy of the DARPA Internet Protocols

Ted Kennedy joke: Congratulates them on their "Interfaith" message processor, thanks them for their ecumenical effortsIn fact, the system crashed at the letter "G" of the word "LOGIN".