a very brief history of early digital networking

Copyright 2012, 2015 & 2016 – Noah Mendelsohn

A Very Brief History of Early Digital Networking

Noah MendelsohnTufts UniversityEmail: [email protected]: http://www.cs.tufts.edu/~noah

COMP 150-IDS: Internet Scale Distributed Systems (Spring 2016)

© 2010 Noah Mendelsohn2

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


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


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






1951: MIT Whirlwind machine goes online (approximate)

1953: Cape Cod System tests sending radar data through phone lines to Whirlwind


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.



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.






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


© 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

14

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 linksfor a fixed route for the life of the call


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

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

1960 1965 1970 1975 1980 1985 1990

ARPANet

Developed

DNS(Mockapetris)

BobMetcalfeBegins

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/


History of the Internet

1960 1965 1970 1975 1980 1985 1990

ARPANet

Developed

DNS(Mockapetris)

MetcalfeBegins

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 doublingin size every 3 months

a very brief history of early digital networking

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