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

surprising; the telegraph was
not only modeled on the railroad, in many parts of the world early telegraph
networks and railway systems were inseparable.' Telegraph wires traveled along railroad rights of way, railroad stations served as telegraph offices,'
and the telegraph was used to let stations up the line know when the train
would be in.

    Telegraph networks were "decentralized": networks with hubs or clusters and with some, but limited, connectivity between the hubs.' Decentralized networks look like railroad connections between major cities and
the suburbs. There are railway connections between a city and its suburbs,
and between the cities, but typically there are no direct connections
between one city's suburbs and another's. For example, all routes from
Cold Spring Harbor, a Long Island suburb, to Boston require travel via New
York City.
    Decentralized systems, however, provide some redundancy of routes.
To travel from New York to Boston, one could take the direct way through
New Haven, or a completely distinct routing, perhaps through Albany and
Springfield. (You might do the latter if the railroad bridge at New London
were out.) A centralized system provides no redundancy; it is like a hotel
switchboard. Everything-calls from one guest room to another, to the
restaurant, front desk, concierge, and so on-is routed through the centralized switch. Figure 2.1 shows a centralized railway network and a decentralized subway network.
    Initially networks were quite local. The subscriber would ring the local
switch and tell the operator the name of the party with whom they wanted
to speak. The first switches were manual, consisting of panels with jacks
and cables between them. The operator would ring that party and then
connect the two lines on the switchboard via patch cords. While the original operators were teenage boys, their antics soon made clear that more
responsible people were needed, and young women became the telephone
operators of choice.' A Missouri undertaker designed the first automated
telephone switch."
    We tend to think of a phone number as the name of the phone at
a particular location, but it is actually something else entirely. As Van
Jacobson, one of the early designers of Internet protocols, once put it, "A
phone number is not the name of your mom's phone; it's a program for
the end-office switch fabric to build a path to the destination line card.i11
    Figure 2.1 (opposite page)
    Centralized versus decentralized networks. Illustration by Nancy Snyder.
    Consider, for example, the U.S. telephone number: 212-930-0800. The
first three digits-the area code-establish the general area of the phone
number; in this case it is New York City. The next three digits, normally called the telephone exchange, represent a smaller geographic area.12 In
our example the last four digits are, indeed, the local exchange's name for
the phone. Taken as a whole, the set of ten digits constitute a route description; the switching equipment within the network interprets that information much like a program and uses it to form a connection.

    The first thing a modern telephone-and I will start by describing just
landline phones-must do is signal that it is "off hook" and thus ready to
make a call. This happens when the receiver is lifted, which closes a circuit,
creating a dial tone and signaling the central office (the local phone
exchange). Then the subscriber can dial the phone number she wishes to
reach ("dial," of course, being an anachronism from the era of rotary telephones). When the central office receives this number, its job is to determine where to route the call.
    If the call is local-that is, within the same area code-then the switches
at the central office need to determine which trunk line, or communication
channel, should be used to route the call to an appropriate intermediate
telephone exchange. This new exchange repeats the process, but this time
connects to the