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Copyright 2012, 2015 & 2016 – Noah Mendelsohn
A Very Brief History of Early Digital Networking
Noah Mendelsohn Tufts University Email: [email protected] Web: http://www.cs.tufts.edu/~noah
COMP 150-IDS: Internet Scale Distributed Systems (Spring 2016)
© 2010 Noah Mendelsohn 2
Shannon &
Information Theory
© 2010 Noah Mendelsohn 3
Claude Shannon and Information Theory
1948: Claude Shannon publishes: A mathematical theory of communication*
* http://cm.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf Photo by Tekniska Museet
© 2010 Noah Mendelsohn 4
Claude Shannon and Information Theory
Shannon’s work is as fundamental to digital communication as Turing’s is to digital computing
Information theory – Quantifies information: how much information does a bit represent? – Relates information transmission to bandwidth requirements – Provides quantitative analysis of rate at which information can be sent over a noisy
channel
Shannon showed that information could be communicated reliably
He predicted how much information could be communicated reliably given that channel characteristics are known
BTW: Shannon and Turing knew each other and met for several months
© 2010 Noah Mendelsohn 5
Whirlwind, SAGE &
US Air Defense
© 2010 Noah Mendelsohn 6
Early history of digital data transmission
1948: Claude Shannon publishes: A mathematical theory of communication*
Late 1940’s: US seeks means of providing cold-war air defense
Late 1949: Digital Radar Relay – experiment sending radar dataover phone lines - first digital transmisison over the phone
1951: MIT Whirlwind machine goes online
© 2010 Noah Mendelsohn
Whirlwind computer
7
© 2010 Noah Mendelsohn 8
Whirlwind computer
The first significant real time computer system
Innovation: core memory & digital networking
5000 vacuum tubes
16 bit parallel ALU
20,000 instructions/second – limited by storage speed
4000 bytes of core memory – invented for Whirlwind
Pictures by Dan Smity
© 2010 Noah Mendelsohn 9
Core Memory
Aside: for 20 years before transistor memories became available, core memory made digital computing practical
© 2010 Noah Mendelsohn 10
Early history of digital data transmission
1948: Claude Shannon publishes: A mathematical theory of communication*
Late 1940’s: US seeks means of providing cold-war air defense
Late 1949: Digital Radar Relay – experiment sending radar dataover phone lines - first digital transmisison over the phone
1951: MIT Whirlwind machine goes online (approximate)
1953: Cape Cod System tests sending radar data through phone lines to Whirlwind
© 2010 Noah Mendelsohn 11
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
Forrester promptly began preparing to receive and process digitized radar signals. The feasibility demonstration of the radar/digital-data concept took place at Hanscom Field in September 1950. The radar, which was an original experimental model of a microwave early-warning unit built by the wartime MIT Radiation Laboratory, closely resembled the radars used in the D-Day invasion of Normandy.
© 2010 Noah Mendelsohn 12
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
Forrester promptly began preparing to receive and process digitized radar signals. The feasibility demonstration of the radar/digital-data concept took place at Hanscom Field in September 1950. The radar, which was an original experimental model of a microwave early-warning unit built by the wartime MIT Radiation Laboratory, closely resembled the radars used in the D-Day invasion of Normandy.
While military observers watched closely, an aircraft flew past the radar, the digital radar relay transmitted the signal from the radar to Whirlwind via a telephone line, and the result appeared on the computer's monitor. The demonstration was a complete success and proved the feasibility of ADSEC's air defense concept.
© 2010 Noah Mendelsohn 13
Early history of digital data transmission
1948: Claude Shannon publishes: A mathematical theory of communication*
Late 1940’s: US seeks means of providing cold-war air defense
Late 1949: Digital Radar Relay – experiment sending radar dataover phone lines - first digital transmisison over the phone
1951: MIT Whirlwind machine goes online (approximate)
1953: Cape Cod System tests sending radar data through phone lines to Whirlwind
1957: First SAGE system, based on Whirlwind technology – SAGE runs US air defenses until 1983! (video) * *
Good book on Whirlwind: Bright Boys, by Tom Green
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
© 2010 Noah Mendelsohn
The SAGE Computer System (AN/FSQ-7)
60,000 vacuum tubes[8] (49,000 in the computers)
Consumed up to 3 megawatts of electricity
Performed about 75,000 instructions per second
Memory: ~65,000 32 bit words
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Source: http://en.wikipedia.org/wiki/AN/FSQ-7_Combat_Direction_Central
© 2010 Noah Mendelsohn 15
Paul Barran &
Packet Switching
© 2010 Noah Mendelsohn 16
Paul Baran, Donald Davies and Packet Switching
1964: Paul Baran proposes packet switching design
Design goal: a resilient network to maintain command and control
© 2010 Noah Mendelsohn 17
Circuit switching (the way the old phone system worked)
When you make a call…
…switches are set to reserve links for a fixed route for the life of the call
© 2010 Noah Mendelsohn 18
Packet switching
When you communicate…
…packets find independent routes through the network
© 2010 Noah Mendelsohn 19
Packet switching
When you communicate…
…packets find independent routes through the network
© 2010 Noah Mendelsohn 20
Paul Baran, Donald Davies and Packet Switching
1964: Paul Baran proposes packet switching design
Design goal: a resilient network to maintain command and control
Questions to consider: – Performance: better or worse than circuit switch?
– How are routing tables maintained?
– Why was it counter-intuitive
Success of early packet switching tests motivates government funding for ARPANet
© 2010 Noah Mendelsohn 21
Packet vs. Circuit Switching
Circuit switching – Good for continuous predictable flows
– Easy to put “smarts” into the middle of the network (smart switches)
– The way to go when all you have is analog communication
Packet switching – Adapts well to changing loads
– Relatively cheap to make lots of quick “connections”
– Paul Baran’s insight: digital makes packet switching possible (packet does not “degrade” as it gets copied through intermediate nodes)
1960’s: AT&T did not believe packet switching would work
Packet switching tends to put value outside the network
When systems are fault-tolerant, you can often build them from cheaper components
© 2010 Noah Mendelsohn 22
A Brief History of The Internet
© 2010 Noah Mendelsohn 23
History of the Internet
1960 1965 1970 1975 1980 1985 1990
ARPANet
Developed
DNS (Mockapetris)
Bob Metcalfe Begins
Ethernet work at
Xerox PARC
Baran & Davies Packet
Switching Work
Prompts Gov’t
Investment
1989: 80,000 hosts
Tim BL Proposes
Web
NSFNet
TCP/IP (Cerf & Kahn)
14 Arpanet Nodes + 1/month
First Web Server
Adapted from http://www.computerhistory.org/internet_history/
© 2010 Noah Mendelsohn 24
History of the Internet
1960 1965 1970 1975 1980 1985 1990
ARPANet
Developed
DNS (Mockapetris)
Metcalfe Begins
Ethernet work at
Xerox PARC
Baran & Davies Packet
Switching Work
Prompts Gov’t
Investment
1989: 80,000 hosts
Tim BL Proposes
Web
NSFNet
TCP/IP (Cerf & Kahn)
14 Arpanet Nodes + 1/month
First Web Server
By 1992, the Internet is doubling in size every 3 months