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Re: A technology that helps the modern world keep running celebrates its 40th anniversary on 5 August. - HERE WE GO AGAIN djf
From: David Farber <dave () farber net>
Date: Thu, 7 Aug 2008 11:49:03 -0700

I know Paul very well at and after RAND and knew Davies as well . They were colleagues in the best sense of the word 
and understood each others contribution to where we are now.   djf


________________________________________
From: Robert Anderson [anderson () rand org]
Sent: Thursday, August 07, 2008 2:16 PM
To: David Farber
Subject: Re: [IP] A technology that helps the modern world keep running celebrates its 40th anniversary on 5 August.  - 
HERE WE GO AGAIN djf

Dave - 1968??  I must remind your audience that Paul Baran published
a very exhaustive set of reports in 1964, based on work he'd done in
previous years, on the concept now called packet switching.  The
following are available for downloading on RAND's website
(www.rand.org):

1964  RM-3767   On Distributed Communications: XI: Summary Overview.
1964  RM-3766   On Distributed Communications: X. Cost Estimate.
1964  RM-3763   On Distributed Communications: VII. Tentative
Engineering Specifications and Preliminary Design for a High-Data-
Rate Distributed Network Switching Node.
1964  RM-3762   On Distributed Communications: VI. Mini-Cost Microwave.
1964  RM-3097   On Distributed Communications: V. History, Alternative
Approaches, and Comparisons.
1964  RM-3765   On Distributed Communications: IX. Security, Secrecy,
and Tamper-Free Considerations.
1964  RM-3638   On Distributed Communications: IV. Priority,
Precedence, and Overload.
1964  RM-3103   On Distributed Communications: II. Digital Simulation
of Hot-Potato Routing in a Broadband Distributed Communications Network.
1964  RM-3420   On Distributed Communications: I. Introduction to
Distributed Communications Networks.
1964  RM-3764   On Distributed Cdmmunications: VIII. the Multiplexing
Station.
1962  P-2626    On Distributed Communications Networks.

Bob A.



On Aug 7, 2008, at 10:26 AM, David Farber wrote:

09:09 GMT, Tuesday, 5 August 2008 10:09 UK
The accelerator of the modern age

It has often been said that change is the only constant in the 21st
Century.

And there is little doubt that the restless tone of these times is
something that the web has helped to accelerate.

But the only reason that the net and the web can cope with that
punishing pace is thanks to work done four decades ago by British
mathematician Donald Davies at the UK's National Physical
Laboratory (NPL).

On 5 August 1968 Dr Davies gave the first public presentation of
work he had been doing on a method of moving data around computer
networks called "packet switching".

The idea may sound mundane but, said John Pethica, chief science
advisor at the NPL, the modern world would be a lot slower without it.

The internet, mobile phone networks and fixed line phones now all
use the principles Davies and his team established to cram as much
data as they can down the cables and wires making up the world's
telecommunication networks.

Clogged pipes

Dr Pethica said the urge to find a better way to handle data
emerged when computer networks were almost unheard of. Donald
Davies, NPL

At that time making a phone call involved creating a dedicated
circuit between the handset of a caller and the person they wanted
to chat to.

"A lot of people realised that point-to-point was going to be a big
problem, even for telephones even before they thought about
computers," said Dr Pethica. "The problem was how you turn it away
from that."

The problem with human speech is that most of it is made up of
silence - be that the pauses between words, time taken to breathe
or gaps when one person waits for another to speak.

Using most of a telephone network to transmit silence is not a very
efficient use of that resource. Far better would be to find a way
to fill the blank spots with the moments from others calls when
those folk were speaking.

Dr Pethica said many in the computer world in the late 60s were
thinking about how to solve this problem.

"There were other ideas around, like Paul Baran at Rand, but they
were nowhere near as useful as what Donald Davies did in terms of
size of packets and nodes," said Dr Pethica.

"It was Donald who had the idea of making a set of nodes that you
send packets of data to that find their own way through," said Dr
Pethica.

The insight of Dr Davies and his team was to slice data, be that a
chat on the phone, an e-mail or a picture, into separate pieces or
packets. These are then put on the network and rely on the
intelligence of nodes in the network to help them wend their way to
their destination. Once there they are re-assembled into the right
order.

Future proof

Dr Pethica said Davies' team worked out the mathematics that
optimised such an approach - an idea that has proved its usefulness
by still being in use today. Computer research at NPL, NPL

Error correction schemes included in the technology helped it cope
with the poor quality of phone lines in use in the late 1960s, said
Dr Pethica. In more modern times those schemes help ensure data
makes it across the busy lanes of the internet.

Davies and his colleagues went further than just establishing the
concept for packet switching - they also build the first computer
networks and proved their ideas could work.

"They had a whole series of early computers at NPL that they turned
in to a local area network (Lan)," said Dr Pethica. He pointed out
that the NPL scientists built such a network far in advance of the
day when such things would become the common way to link up
machines in an office.

"The important breakthrough that he and his team made was to build
the Lan and make it work," he said.

Even before Dr Davies presented his work publicly, news of it had
spread through the international computer science community.

As a result he was invited to talk about it to a team from the US
Advanced Research Project Agency (Arpa) working on the fledgling
internet. The principles he established were rolled in to the
technology to make that network function.

Dr Pethica said packet switching idea was developed with an eye on
the future and how a computer network might grow. Forty years on
the scalability in the Dr Davies insight is still proving its
worth, he said.



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