Computer Networks Spring 2007 January 17, /S07

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

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

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

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 and a networks class at Georgia Tech See website for link to the site Create accounts soon.

Background A “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 TCP 441/F06/ 441/F06/

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

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— 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 Express 1861 AD: The Pony Express mi/day, 1966 mi from Missouri to California, 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

Chappe ( ), a “defense contractor”; 1st message successfully sent in : 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 Visual communications: The optical telegraph

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

The Electric Telegraph Cooke and Wheatstone, Railroad Telegraph, mi installed by mi by 1852

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

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)

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 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

Wireless! James Clerk Maxwell ( ) "... 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, Heinrich Hertz ( ) 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 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

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

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)

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 : Western Union competes using rival system designed by Thomas Edison and Elisha Gray. Bell sues and wins.

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

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

“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

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

ARPANET & Internetworking BBN team that implemented the interface message processor 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

ARPANET Topology in 1969 First inter-site demo, 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 program (BBN), various demos and apps; CYCLADES effort in France; telnet spec 1973, APRANET becomes international , internetworking effort (Kahn & Cerf, et al.) 1973, Bob Metcalfe’s Harvard thesis: Ethernet 1976, UUCP distributed by AT&T 1978, TCP and IP split (end-to-end principle) 1980, ARPANET grinds to halt due to a virus Robert Morris (Cornell; now MIT)

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

Some Decentralized Administration (1987)

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

Year 2000

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

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

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

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

For Next Time Please read The Design Philosophy of the DARPA Internet Protocols