Surveillance or Security?: The Risks Posed by New Wiretapping Technologies Read Online Free PDF Page B

Such redundancy is surprisingly cheap to obtain. Say a
network has redundancy 1 if there are exactly enough wires connecting the
nodes so that there is one path between any two nodes; if there are twice
as many wires, call that redundancy 2, and so on.20 Trying experiments
on more traditional communications networks, Baran ran simulations and discovered that with a redundancy level of about 3, "The enemy could
destroy 50, 60, 70% of the targets or more and [the network] would still
work.i21 The design resulted in a highly robust system.

    The distributed networks that Davies and Baran had independently
invented were to be even more decentralized than decentralized networks
of earlier efforts. Network redundancy meant that paths might be much
longer than the typical PSTN communication. Thus the communications
signal had to be digital, not analog. That turned out to be a tremendous
advantage. There was no need for the entire data transfer to occur in one
large message; indeed, efficiency and reliability argued that the message
should be split into small packets.
    The idea was that when the packets were received the recipient's
machine sent a message back to the sender saying, "OK; got it." If there
was no acknowledgment, after a short period, the sender's machine would
resend the packet. Of course, because the packets traveled by varied routes,
they might arrive out of order. But the packets could be numbered, and
the receiving end could simply sort them back into order.
    One of the striking things about this proposed network was that while
the network itself was to be extremely reliable, individual components
need not achieve that same level of reliability. Instead the network
depended on "structural reliability, rather than component reliability.""
Small amounts of redundancy led to vastly increased reliability, a result
surprising to the engineers.23
    The Internet's decentralized control meant all machines on the network
were, more or less, peers. No one computer was in charge; the machines
were more or less equal and more or less capable of doing any of the
communication tasks. A computer could be the initiator or recipient of
a communication, or could simply pass a message through to a different
machine. This is the essence of a peer-to-peer network, and very much the
antithesis of the telephone company's hierarchical model of network
communication.
    In Britain, the telecommunications establishment supported Davies,24
but in the United States Baran received a chilly reception from AT&T.
Baran was turning all the ideas that AT&T had used to manage their system
upside down. While scientists at the research arm of AT&T were quite
excited by Baran's work, corporate headquarters viewed that approbation
as the reaction of head-in-the-cloud scientists and refused to have anything
to do with Baran's packet-switched network.25 The odd thing about all this
was that the new network was not actually a new network at all. Baran
had built his network on top of the existing telephone network built by Alexander Graham Bell and his successors. It "hooked itself together as a
mesh,i26 simply connecting everything in new ways.

    Scientific and technological ideas often emerge when the time is ripe,
and Baran and Davies were not the only ones to be considering packetswitched networks. (The actual term packet is due to Davies, who wanted
to convey the idea of a small package.) In 1961, Leonard Kleinrock, then
a graduate student at MIT, published the first of a series of papers analyzing
the mathematical behavior of messages traveling on one-way links in a
network. This analysis was critical for building a large-scale packet-switched
network.
    One could say, only partially tongue in cheek, that the Internet is due
to Sputnik, the Soviet satellite that in 1957 startled the United States out
of its scientific complacency. In response the U.S. government founded the
Defense Advanced Research Projects