ARPA WAS NEARLY BEATEN TO IT by the British, who from 1968 had
a local area network of their own, the NPL Data Communications
Network operated in London’s National Physical Laboratory. It
was based on designs by Donald Davies, the inventor of packet
switching, and operated until 1986. Davies’ ideas included a
national commercial data network and, in 1966, his team produced
a design for the laboratory network, including the concept for an
‘interface computer’ we’d call a router.
The NPL ideas were presented at the Symposium on Operating
Systems Principles, a conference held in 1967 in Gatlinburg,
Tennessee. The plan for ARPANET was also presented there,
by Larry Roberts of ARPA, and he took away with him many of
Davies’ concepts, including the speed at which it should operate.
ARPANET was originally designed to run at a transmission
rate of 2.4kbit/s, but this was upgraded to 50kbit/s after NPL’s
remarkable 786kbit/s line speed.
Independently, Paul Baran of the RAND Corporation had
come up with a similar idea to packet-switching, published in
his papers titled ‘On Survivable Communications’, but called
the packets ‘message blocks’. However, his work lacked Davies’
breakthrough idea that computer network traffic comes in
bursts, not a constant flow like a phone conversation. It was this,
along with the ability of the routers (known as IMPs, or Interface
Message Processors) to route traffic around failures as long as
a path could be found, that fed into one of ARPANET’s disputed
design goals. Baran’s work was meant to survive and adapt in the
event of a nuclear attack. Was ARPANET?
On the ‘no’ side is Charles Herzfeld, ARPA director 1965-1967,
who wrote “The ARPANET was not started to create a Command
and Control System that would survive a nuclear attack, as many
now claim... Rather, it came out of our frustration that there were
only a limited number of large, powerful research computers in
the country and that many research investigators, who should
have access, were geographically separated from them.”
This sounds extremely altruistic, but is countered by Stephen
J Lukasik, director of DARPA (it gained the ‘D’ in 1972 and lostit again in 1993, only for it to return in 1996) from 1970 to 1975,
who said: “The goal was to exploit new computer technologies to
meet the needs of military command and control against nuclear
threats, achieve survivable control of US nuclear forces, and
improve military tactical and management decision making.”
Whether it was deliberate or not, the ARPANET ended up being
inherently survivable thanks to its distributed nature and the
ability to recompute routing tables to take account of nodes that
suddenly stop responding. “One of the questions that gets asked
and statements made is that this was a defense department
project and it was the Cold War, so it must have been motivated
by nuclear survivability,” says Steve Crocker, who formed the
Networking Working Group with Vint Cerf in 1969 as a UCLA grad
student. “The short answer to that is ‘no’,” he says. “But the long
answer is a bit more complicated.”
We like a complicated answer, so let’s have it. “In the funding
process from a multi-layered bureaucracy, there’s a lot of latitude
at different levels,” says Crocker. “And so, depending upon how
much you’re spending and what buttons you’re pushing, some
things take place without a great deal of major focus and other
things rise to the level of national prominence, and get sorted out
in the newspapers and in Congress.
“Fundamentally, this network was motivated by how you
communicate across laboratories, how you foster interactivity,
how you make computers more useful and do that in a distributed
sense. On the other hand,” Crocker says, “it was also evident that,
since this was being funded by the Department of Defense, there’s
a question of its military relevance. The vast majority of military
communications have nothing to do with weapons, it’s how do
you know where all your people are? How do you know whether
you’ve ordered enough toilet paper? Lots of planning documents,
a big bureaucracy that runs on communications. So, to justify the
project in terms of how it will affect military communications is
easy in a broad sense. On occasion, there were discussions about
how someday in the future, this technology might be useful for
deciding how to build future survivable networks.
The IMP team at
Bolt Beranek and
Newman. Robert
Kahn is fifth from
the left, in black.getting connected
40 MAXIMU MPC APR 2022
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