Surveillance or Security?: The Risks Posed by New Wiretapping Technologies (7 page)

While IP addressing can handle portability, it has some trouble with
mobility. Being connected is a heavy-duty operation-it sends signals
down the line that the IP address, which designates the physical location
of the device, is such-and-such. An IP address, say for routing a piece of
email or downloading a movie, needs to be stable for at least the duration of the data being transferred to it. That stability is quite complicated to
achieve when the user is mobile, and the problem has not been fully solved
yet. (What appears to be IP connectivity on a moving vehicle-for example,
the web browsing now available on some planes-is actually a local IP
network connecting to the Internet via a cell link. The IP address does not
change as the device moves.)

If Internet communications have not fully sorted out how to handle
highly mobile communications, another community had that problemand solution-as its raison d'etre. Cell phones allow users to communicate
while moving. This is not always easy; for example, if the speaker is on a
high-speed train, special technology is needed so that the call is not
dropped.52 There are two parts to enabling the mobility of cell phone users.
Cell phones (called mobile phones in Europe) rely on a network of radio
towers to transmit the communication. But a cell phone is not fixed in
space and so the system also needs a way to determine that the user has
paid for services. Thus each user is registered in a Home Location Register
(HLR), a very large database that stores subscriber information (including
to what services users are entitled) about all users in that home location.
Users are assigned to a particular HLR based on their phone number.53 That
solves part of the problem, but, of course, cell phone subscribers are
mobile. So as a subscriber moves about the network, information about
the user's privileges on the network must also travel. Otherwise there is
simply too much delay in completing calls while the network checks back
with the HLR. In addition to the HLR there is a local, smaller database
called the Visitor Location Register (VLR) that contains a portion of the
subscriber's information.

Calls are handed from tower to tower as the phone subscriber moves
during a conversation. These towers, or base stations, are divided into
groups called Location Areas. When a cell phone is turned on, the phone
identifies itself through its phone number to the nearest tower (note that
unlike a telephone on the PSTN, a cell telephone number is definitely not
a program used to define the phone's location). By checking in with the
appropriate HLR (easy to determine from the phone number), the base
station grants the phone service.

When a roaming phone is initially turned on, and maybe every thirty
minutes after that, a signaling message is sent from the phone to the HLR.54
This enables the HLR to route calls to the subscriber. The first time a
roaming subscriber tries to make a call, the HLR is queried: to what services
is the subscriber entitled? After that, the VLR is established in the new
Location Area; all queries go to it, rather than the HLR. (This is why the initial call made while roaming may take longer to connect than subsequent ones.) A new VLR is created whenever a subscriber crosses into a
new Location Area.

2.6 Voice on the Data Network

In the Internet, voice communications systems did not happen until
several decades after written applications (such as email). There was one
exception: in 1973 an engineering team led by Danny Cohen of the Information Sciences Institute (ISI) of the University of Southern California used
the ARPANET to make calls between ISI and MIT Lincoln Lab in Lexington,
Massachusetts.55 At the time, the entire cross-capacity of the ARPANET was
only two or three 56-kilobit lines, the equivalent of two or three dial-up
modems. A voice call, which is very rich in data, could use up the entire
capacity. Thus the issue was how to compress the data rate for voice calls
way down. While current voice calls use about 64 kilobits for a call, the
1970s effort did the call using just 2 to 3 kilobits.56 "Remember, the phone
companies were looking over our shoulders laughing," Cohen recalled
years later, "and our job was just to prove it could be done. We did. 1117

The network did not have reasonable bandwidth for voice calls until the
mid-1990s. Speed was part of the problem. While emails can take a few
seconds to transit their route and that presents no difficulty, people will
drop a phone conversation if there is as much as a half second delay in
transmission. Early versions of the network were too slow to support realtime voice compression that, in the 1970s, took two or three cabinets of
cutting-edge electronics to achieve. Today's Internet is much faster than the
ARPANET of three decades ago, and such compression is no longer needed.
Voice communications over the Internet, known as VoIP, has arrived.

VoIP means that the voice conversation is routed over a network using
the Internet Protocol. This network could be the Internet itself or it could
be a smaller regional or local network. Though the communication is a
real-time voice communication like a phone call, the technology is not
like the PSTN. Unlike the dedicated circuit that is established for a telephone call, at some point during the call, a VoIP communication is converted into packets that are sent over an IP-based network and then
reassembled at the endpoint.

The simplest form of VoIP-and the first to come onto the market-was
transparent to the user. The caller uses a telephone to make the call which
then travels, as it would normally, to the telephone company's central
office. There the call is converted to a digital signal, sent over an IP-based network to its destination; at the final hop to the recipient, it may change
to an analog signal (whether it does so depends on the type of phone and
network being used). This is the model that Vonage employed.

Of course, there is no reason that the customer's telephone has to be
an old-style voice phone; it could be a more modern IP-based telephone.
To the user the device itself looks-and acts-like a telephone, but its
innards and actions, as well as the connection to the outside world, are
quite different. The telephone converts the signal from analog to digital
and connects to a data network rather than the telephone network.

There is also a VoIP model that fully dispenses with the telephone; one
uses a computer to make the call and the Internet is used for routing the
communication (to another computer). This is how Skype58 works, but
Skype goes one step further. Skype is a fully peer-to-peer based VoIP system:
any machine running Skype may be used in the transmission of another
Skype user's call.59 Skype is a realization of Baran's peer-to-peer model of
communication. Just as the telephone company executives observed, this
communication system turns the telephone network model upside downleaving the utility to provide only the underlying wires.

The difference in networks means that the "phone" is not quite a telephone; this causes important differences. The telephone network is powered
by electricity but because PSTN telephones are powered from the central
office, the telephone network tends to stay up even when the electric
power grid goes down. Another issue is that IP-based telephones can run
into quality-of-service problems: if the network is being heavily used, communication quality can suffer. On the PSTN the situation is handled differently: either the call goes through and there is a steady connection or
one hears: "All circuits are busy now. Please try your call again later." Yet
another distinction is that Internet users do not necessarily know the IP
address of the person they wish to "call" using VoIP. Because the Internet
enables mobility, there is no "phone book" of IP addresses, which are often
allocated dynamically. The user can have a different IP address each time
they log on. In the space of an hour, the caller can move from a hotel
lobby to a cafe to an airport lounge. Most VoIP systems use a rendezvous
service that transforms a user identifier (e.g., a telephone number, screen
name, email address) into the user's current IP address."

2.7 Data on the Voice Network

While the Internet has enabled voice communications over what was
originally a data network, the telephone network has gone the other way: simplifying text transmission over a voice network. This is texting, also
called SMS.61 Texting arose from telephone signaling capabilities developed
in the 1980s. Once call setup information traveled on the same channel
as voice communications, but as communications systems moved to digital
transmission, an out-of-band channel was needed for transmitting the
signaling information. Thus Signaling System 6 (SS6), a packet-based digital
protocol for network control, was developed in the 1970s; it has since been
replaced by Signaling System 7 (SS7), which is more versatile. SS7 uses two
conduits: a Call Content Channel (CCC) that is typically, though not necessarily, used for voice communications, and a separate call signaling channel,
the Call Data Channel (CDC). This architecture enables such advanced
telephony features as caller ID, call forwarding, and voice mail.

When the CDC is not in use, it could be put to other purposes. One
such is enabling the transmission of short text messages between users;
that is the essence of SMS.62 SMS lets users send 140-character-long messages from the keypad of their cell phones.63 It was introduced by European
commercial carriers in 1993. The carriers did not use the same standard
for texting, and originally text messages could not be sent between networks. Once that issue was resolved, texting took off. By 2003, over 70
percent of Europeans were using text messaging.64 The telecommunications companies expected businesspeople to be the SMS users, but the
biggest market for SMS turned out to be teenagers, a pattern echoed in
other parts of the world.

Texting is popular in Asia, where adoption of personal computers lags far
behind that of western Europe and the United States,65 and the cell phone
is the communications device of choice. One in three Chinese has a mobile
phone, and China is responsible for over 300 billion SMS communications
annually. The Asia-Pacific region and Japan sent an estimated 1.5 trillion
messages in 2007,66 and that number is only expected to grow. Everyoneteenagers, families, businesspeople, commuters-uses text messaging. Japan
was an early leader in texting. Japan's use is far broader than simple messages: five of 2007's bestselling novels were originally published via cell
phones.67 Japan's texting technology is, however, different from most other
nations': it is IP-based rather than using cell phone technology.

Texting can be used for fun and games, but it is also used for business.
That is its primary purpose in Africa. On a continent where transport and
wired communications are unreliable, SMS technology is a true business
enabler.68 As is the case throughout the world, the asynchrony of text
messaging is part of its attractiveness as a communications medium. Sometimes texting can be used for serious political business. In 2001, Philippine President Joseph Estrada was ousted after hundreds of thousands of people,
summoned to the streets by text messages, protested a vote that would
have cleared the president of wrongdoing.69 Even China, which carefully
controls communication channels and political activities, has had political
protests organized through texting.70

When it comes to text messaging, the United States is out of sync with
the rest of the world. The U.S. marketplace-based approach to cell phones
meant that unlike in Europe, there was no government mandate of a cell
phone standard. Carrier interoperability for SMS messaging did not occur
until 2002. Text messaging took off more slowly in the United States than
it did in the rest of the world and is, relatively speaking, expensive."

SMS is not without limitations. There is no guaranteed message delivery.
Furthermore, depending on the type of routing the message takes, the text
message may not receive the privacy protections of regular telephone communications but instead have only the lesser protections typical of email.72

2.8 Who Calls-and What Do They Communicate?

For a time, the telephone was the communications medium of choice. In
1960 people in the United States made about 100 billion domestic telephone calls73 and only 42 million international ones annually.14 By 1990
those numbers had increased to 402 billion and 984 million respectively.75
In 2004, the increase was not particularly striking; the numbers went up,
respectively, to 420 billion calls domestically and 10.9 billion overseas.76
That was because Americans were turning to wireless: Americans used
thirty-one billion minutes of wireless in 1995 and seventy times as much
by 2008 (2.23 trillion minutes annually)." Meanwhile during the period
from 1990 to 2004, more than 70 percent of the U.S. population began
using the Internet.78 Texting finally caught on, going from 75 billion text
messages sent in 2005 to 600 billion in 2008.79

The design objective behind the PSTN was to maximize voice quality
throughout the network. Depending on the language and emotions being
expressed, human speech appears in many patterns, and the human voice
in many timbres. Yet regardless of whether the conversation is in Chinese,
Aramaic, English, or Hindi and whether the speaker is an adult male, a
small child, a young woman, or an older one, speech and voices fall into
a fixed acoustic range. The same PSTN equipment can be used in Beijing
as in Bangalore without an effect on the quality of transmittal of the
speaker's utterances. Data are simpler but more fluid. Bits are Os or Is, yet
they can be used to represent nearly anything: a laundry list, an Instant Message conversation, course grades in a database, a blueprint, a photo
from Mars, the results from a search query, the census.

Because data varies tremendously, Kahn's design principles were simple:
deliver the data and do so efficiently. Or to put it another way: assume the
recipient herself will know how to maximize quality for her own particular
application. That "the function in question can completely and correctly
be implemented only with the knowledge and help of the application
standing at the endpoints of the communication systemi80 came to be
known as the end-to-end principle. It is the guiding principle of Internet
design, and this essential idea underlies the network's versatility.