A Very Brief History of Early Digital Networking COMP 117: Internet Scale Distributed Systems (Spring 2017) A Very Brief History of Early Digital Networking Noah Mendelsohn Tufts University Email: noah@cs.tufts.edu Web: http://www.cs.tufts.edu/~noah

Shannon & Information Theory

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

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

Whirlwind, SAGE & US Air Defense

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

Whirlwind computer

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

Core Memory Aside: for 20 years before transistor memories became available, core memory made digital computing practical

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

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. 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. History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html

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

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 Source: http://en.wikipedia.org/wiki/AN/FSQ-7_Combat_Direction_Central

Paul Barran & Packet Switching

Paul Baran, Donald Davies and Packet Switching 1964: Paul Baran proposes packet switching design Design goal: a resilient network to maintain command and control

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

Packet switching When you communicate… …packets find independent routes through the network

Packet switching When you communicate… …packets find independent routes through the network

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

Packet vs. 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

A Brief History of The Internet

History of the Internet DNS (Mockapetris) First Web Server 14 Arpanet Nodes + 1/month NSFNet 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 ARPANet Developed TCP/IP (Cerf & Kahn) 1960 1965 1970 1975 1980 1985 1990 Adapted from http://www.computerhistory.org/internet_history/

History of the Internet DNS (Mockapetris) First Web Server 14 Arpanet Nodes + 1/month NSFNet By 1992, the Internet is doubling in size every 3 months Baran & Davies Packet Switching Work Prompts Gov’t Investment Metcalfe Begins Ethernet work at Xerox PARC 1989: 80,000 hosts Tim BL Proposes Web ARPANet Developed TCP/IP (Cerf & Kahn) 1960 1965 1970 1975 1980 1985 1990