Hardware Reference
In-Depth Information
• Leased lines
At least one of these services should be available to you, and if you live in a medium- to
large-size city, you might be able to choose from several broadband solutions. The first
portion of this chapter focuses on these solutions.
Cable TV
Cable TV (CATV)-based Internet piggybacks on the same CATV service lines used for
cable television service.
The device used to connect a PC to a CATV network is called a
cable modem
. In fact,
the so-called “cable modem” is actually a great deal more. The device does indeed mod-
ulate and demodulate, but it also functions as a tuner, a network bridge, an encryptor, and
a Simple Network Management Protocol (SNMP) agent. To connect your PC to a CATV
network, you do not use a serial port as with dial-up modem technologies or Integrated
Services Digital Network (ISDN) terminal adapters. Instead, the most typical connection
today runs the incoming cable connection to an external cable modem, which has an Eth-
ernet connection to a router, which then connects from 1-255 PCs via Ethernet. Although
youcan directly connect a PC to a cable modem using Ethernet or(in some cases) univer-
sal serial bus (USB), I do not recommend that option because it precludes using a router.
I always recommend running a router between a cable, digital subscriber line (DSL), or
satellite modem and a PC because a router not only allows more than one PC to be con-
nected, but also provides a robust hardware firewall that helps shield the PCs connected
to it from Internet-based attacks. Some cable modems have a built-in wireless router, in
which case you don't need to purchase a separate one.
Tip
For maximum security, speed, and ease of sharing among multiple systems, I recommend
that you connect your cable modem (if it doesn't include its own router) to a router and then
connect the router to an Ethernet card or port in your system. Combination cable modems
androutersareavailablethatincludebothfunctionsinonebox.Thesedevicesaresometimes
referred to as cable gateways.
Cable Modems
ThecablemodemconnectstotheCATVnetworkusingthesamecoaxialcableconnection
as the cable TV service (see
Figure 16.1
). Thus, the cable modem functions as a bridge
betweenyournetworkandthehybridfiber/coax(HFC)networkthatconnectsallthecable
customers in your neighborhood.
Figure 16.1
A typical hybrid fiber-coax cable TV network that also includes two-way cable modem ser-
vice.
