But the devices that use the highway system are highly regulated. You can't
take a go-cart onto Route 66; you can't drive a tank down your local street.
Regulations control the devices that can be used on a highway. But regula-
tion does not control who gets to go where. Use remains, in our terms, free.

The same could exist for spectrum. But to see how, we need to think a bit
differently about what spectrum is and how it is used. As David Reed says of
policy makers, so is it for most of us: We are "grounded in theory or com-
mon sense [about spectrum] that does not match the phenomena we are
seeing every day."[5-20]

///\\\

To understand the possibility of free spectrum, consider for a moment
the way old versions of Ethernet worked. Ethernet is the protocol you most
likely use to connect your computer to your company's local area network.
If you have a cable modem at home, it is the protocol used to connect your
computer to the cable modem. It is essentially a way for many devices on a
single network to "share" the resources of that network. But the critical fea-
ture of this sharing is that it occurs without any central authority deciding
who does what when.

How?

When a machine on an Ethernet network wants to talk with another
machine -- when it wants, for example, to send content to a printer, or to
send an e-mail across the Internet through an e-mail server -- the machine
requests from the network the right to transmit. It asks, in other words, to re-
serve a period of time on the network when it can transmit. It makes this
reservation only if it hears that the network at that moment is quiet. It be-
haves like a (good) neighbor sharing a telephone party line: first the neigh-
bor listens to make sure no one is on the line, and only then does she
proceed to call. Likewise with the old versions of Ethernet: the machine
would first determine that the network was not being used; if it wasn't, it
would send a request to reserve the network.[5-21]

What if two machines sent that request at the very same time? If that hap-
pened, the network would record a "collision" on the network, and each
machine would register that its request had failed. Each machine would
need to request access to the network again. But rather than each machine
requesting access at the same time, each waits for a random amount of time
until it sends its request again. Ethernet technologies demonstrate that this
protocol for dealing with collisions is quite good at facilitating coordinated
use of a common network.

[[77]]

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